Soil Improvement

The ground is a natural grand system; it is composed of myriad constituents that aggregate to form several geologic and biogenic systems. These systems operate independently and interplay harmoniously via important networked structures over multiple spatial and temporal scales. This paper presents arguments and derivations couched by the authors, to first give a better understanding of these intertwined networked structures, and then to give an insight of why and how these can be imitated to develop a new generation of nature-symbiotic ground engineering techniques. The paper draws on numerous recent advances made by the authors, and others, in imitating forms (e.g. synthetic fibres that imitate plant roots), materials (e.g. living composite materials, or living soil that imitate fungi and microbes), generative processes (e.g. managed decomposition of construction rubble to mimic weathering of aragonites to calcites), and functions (e.g. recreating the self-healing, self-producing, and self-forming capacity of natural systems). Advances are reported in three categories of Materials, Models, and Methods (3Ms). A novel value-based appraisal tool is also presented, providing a means to vet the effectiveness of 3Ms as standalone units or in combinations.

Abstract
Stable isotope analyses of faunal remains provide valuable information about human–environment interactions in the past, including insights into past animal husbandry and land management strategies. Here, we report stable carbon (δ13C) and nitrogen (δ15N) isotope values of collagen and carbonate from archaeological fauna from Kałdus, a medieval settlement in North-Central Poland, to better understand human–environment interactions during a period of increasing urbanism and marketization. Wild and domestic animals can be separated on the basis of their isotopic values. The mean δ15N value for 12 domesticated animals is 7.6 ± 1.2‰ and for 5 wild animals is 4.3 ± 0.5‰ (p = 0.002). The mean collagen δ13C value for domesticated animals is −20.6 ± 1.1‰ and for wild animals is −22.0 ± 0.5‰ (p = 0.004). The mean carbonate δ13C value for domesticated animals is −13.14 ± 1.3‰ and for wild animals is −14.14 ± 0.9‰ (p = 0.034). The “canopy effect” and anthropogenic effects that alter stable isotope ratios of plants (manuring, swidden agriculture and ploughing) are discussed in relation to these differences. Fish are isotopically variable, which suggests broad-spectrum fishing strategies and/or trade, and increases our awareness of the difficulties in interpreting human paleodiet when freshwater fish were on the menu.

Microbial-Induced Calcite Precipitation (MICP) has recently emerged as a sustainable technique for soil improvement. This paper aims to study the effectiveness of MICP in improving the shear strength and reducing the hydraulic conductivity of soils. A species of Bacillus group, B. megaterium was used to trigger the calcite precipitation. The experimental variables included soil types (tropical residual soil and sand), soil densities (85%, 90%, and 95% of their respective maximum densities), and treatment conditions (untreated, treated with cementation reagents only, treated with B. megaterium only, and treated with B. megaterium and cementation reagents). The results showed that MICP could effectively improve shear strength and reduce hydraulic conductivity for both residual soil and sand. The improvements, however, varied with soil densities, soil types, and treatment conditions. With MICP treatment, the improvement ratios in shear strength of the residual soil specimens were significantly higher (1.41-2.64) than those of the sand specimens (1.14-1.25). On the contrary, the sand specimens resulted in greater hydraulic conductivity reduction ratios (0.09-0.15) than those of the residual soil specimens (0.26-0.45). These observations can be explained by the particle-particle contacts per unit volume and pore spaces in the soil specimens. Both soil specimens when treated with cementation reagents only exhibited slight alterations in the shear strength (ranging from 1.06-1.33) and hydraulic conductivity (ranging from 0.69-0.95). The results implied that natural calcite forming microorganisms only exist for insignificant amount. The amount of calcite precipitated in the treated residual soil specimens ranged from 1.080% to 1.889%. The increments of calcite content in the treated sand specimens were comparatively higher, ranging from 2.661% to 6.102%. The results from Scanning Electron Microscope (SEM) analysis confirmed the experimental findings.

The degree of consolidation is usually used as one of the criteria for assessing the effectiveness of soil improvement work using the fill surcharge or vacuum preloading method. It is also often used as a design specification in a soil improvement contract. Degree of consolidation is normally calculated using settlement data. However, as the effect of vacuum preloading is controlled largely by pore water pressure changes, it is necessary to analyze the pore water pressure variations and to assess the degree of consolidation using pore water pressures. In this paper, the problems involved in the estimation of degree of consolidation using settlement data are discussed. A method to estimate the average degree of consolidation using pore water pressure data is suggested. Two case studies are presented to examine the characteristics of the pore water pressure variation of soil under vacuum loading. The degree of consolidation achieved in each of the two cases is assessed using pore water pressure data and compared with that estimated using settlement data. Factors affecting the degree of consolidation assessment are discussed.

This paper investigates the fluidity and rheological properties of the cement based grout mixed with rice
husk ash (RHA). The experimental program consisted of fifteen different mixture having 5%, 10%, 20%, and
30% RHA content and three different water to binder ratios (w/b = 0.75%, 1.00%, and 1.25%). Workability
properties (marsh cone flow time, plate cohesion, and mini slump diameter), plastic viscosity, apparent
viscosity, and the yield stress of the mixtures were determined. Test results showed that increasing
replacement level for the RHA amount increases marsh cone flow time, plate cohesion, plastic and
apparent viscosity, and the yield stress, but also decreases mini slump diameter. Shear thickening and
pseudo-plastic behavior was observed for high RHA content for w/b ratios greater than 1.00.

This laboratory study examines the potential use of an anionic polyacrylamide (PAM)-based material as an environmentally sustainable additive for the stabilization of an expansive soil from South Australia. The experimental program consisted of consistency limits, sediment volume, compaction and oedometer cyclic swell–shrink tests, performed using distilled water and four different PAM-to-water solutions of PD = 0.1 g/L, 0.2 g/L, 0.4 g/L and 0.6 g/L as the mixing liquids. Overall, the relative swelling and shrinkage strains were found to decrease with increasing number of applied swell–shrink cycles, with an 'elastic equilibrium' condition achieved on the conclusion of four cycles. The propensity for swelling/shrinkage potential reduction (for any given cycle) was found to be in favor of increasing the PAM dosage up to PD = 0.2 g/L, beyond which the excess PAM molecules self-associate as aggregates, thereby functioning as a lubricant instead of a flocculant; this critical dosage was termed 'maximum flocculation dosage' (MFD). The MFD assertion was discussed and validated using the consistency limits and sediment volume properties, both exhibiting only marginal variations beyond the identified MFD of PD = 0.2 g/L. The accumulated axial strain progressively transitioned from 'expansive' for the unamended soil to an ideal 'neutral' state at the MFD, while higher dosages demonstrated undesirable 'contractive' states.

Chalk breaks easily when subjected to human action such as mechanical handling, earthworks operations or pile instal- lation. These actions break the cemented structure of chalk, which turns into a degraded material known as putty, with lower strength and stiffness than the intact chalk. The addition of Portland cement can improve the behaviour of chalk putties. Yet, there are no studies determining the tensile strength of chalk putty–cement blends, the initial stiffness evolution during the curing time and other design parameters such as friction angle and cohesion of this material. This paper addresses this knowledge gap and provides an interpretation of new experimental results based on the dimensionless index expressed as the ratio between porosity and volumetric content of cement (g/Civ) or its exponential modification (g/ Civa). This index aids the selection of the amount of cement and density for key design parameters of compacted chalk putty–cement blends required in geotechnical engineering projects such as road foundations and pavements, embankments, and also bored concrete pile foundations.

Liquefaction is a hazardous seismic-based phenomenon, which causes an abrupt decrease in soil strength properties and can result in the massive destruction of the built environment. This research presents a novel approach to reduce the risk of soil liquefaction using jet-grouted micropiles in clean sands. The saturated soil profile of the study project mainly contains clean sands, which are suitable to more reliably employ simplified soil liquefaction analyses. The grouting is conducted using 420 micropiles to increase the existing soil properties. The effect of jet grouting on reducing the potential of liquefaction is assessed using the results of the cone penetration test (CPT) and the standard penetration test (SPT), which were conducted before and after jet grouting by implementing micropiles in the project sites. According to three CPT-based liquefaction analyses, the Juang method predicts the most effective improvement range of the factor of safety in the clean sand. The Boulanger and Idriss, and Eurocode methods show comparable evaluations. Results of the SPT-based analyses show the most considerable increase of the factor of safety following the Boulanger and Idriss, and NCEER approaches in the SP soil. CPT- and SPT-based analyses confirm the effectiveness of jet grouting by micropiles on enhancing soil properties and reducing the risk of liquefaction.

A finite element soil–structure interaction model is coupled with a discrete auto-regressive code, in order to analyze
the effect of added spatial variability due to soil improvement in seismic risk analysis. The success of soil
improvement techniques is related to the effectiveness of the method – that is, how much of the soil is being
changed – but also to its efficiency in improving the soil behavior – that is, how much are the liquefaction and
liquefaction-induced settlement reduced. As these techniques can add spatial variability to a deposit, it can affect
the triggering of liquefaction on the soil and the behavior of the structures above it. In this study, this
heterogeneity is modeled as a binary mixture, composed by the original liquefiable sand and the added treated
sand. The soil behavior is represented by a fully nonlinear elastoplastic multi-mechanism model. The co-seismic
settlements of the structure and the liquefaction of the soil deposit are estimated for different effectiveness
levels – measured by mixture fractions – and for different spatial distributions. In general, both very small or
very high mixture fractions presented low efficiency as the improvement in the relative settlement was small.
Additionally, results show that the interaction between loose and dense deposits is highly dependent on
the spatial distribution. Therefore, homogeneous equivalent models will rarely correspond to the average of the
heterogeneous response

Under earthquake motions, effective stress decreases with pore water pressures. It falls to zero or near-zero values in saturated sandy soils, and consequently, the bearing capacity of the soil is ultimately lost. This phenomenon is called liquefaction. One of the most effective methods used to prevent liquefaction on sandy soils is stone column applications. The stone column applications increase the drainage capacity and the stiffness of the soil. Thus, excess pore water pressure, which develops under dynamic loads, reduces and minimizes liquefaction risks. In this study, the finite element method (FEM) was used with the hypoplastic material model. This model gives more realistic results under repeated loads since the change in the soil unit weight and the effect of the stress level on the soil behavior are taken into account. Since the model was not defined in the ANSYS program, u20p8, a two-phase three-dimensional finite element, was developed for numerical analyses and implemented in the program with the hypoplastic material model. The effect of stone columns to prevent liquefaction on fully saturated sandy soils under dynamic loads and the factors affecting the performance of stone columns were investigated with parametric studies. The results of the analyses revealed the preventive effect of the use of stone columns. They showed that increasing the parameters such as area ratio, hydraulic conductivity, and relative density increased this positive effect more. When the correct designs are made according to the soil properties, the stone column application method provides an effective soil improvement against liquefaction.

The construction of railway embankments on loose beds using reinforcing elements results in a modification of the embankments slope, which significantly reduces the amount of earthworks. In addition, reinforcement of both bed and embankment is essential to increase the load-bearing capacity and control the settlements. A solution for high railway-embankment stabilization and enhancing the operational axle load is the use of micropiles in the embankment toe to transmit the applied loads to the firm underlying layers and avoid the deep sliding of loose subgrade. This paper presents three experimental models of embankments of 10 m in height on a scale of 1=20 to set up a number of loading tests: one based on a non-reinforced embankment and two others based on reinforced embankments that are stabilized with two different arrangements of micropiles. During laboratory tests, the data, including the load-bearing capacity of embankments, displacements of embankment crest and bed surface, and axial strain of micropiles were measured using the instrumentation tools. In the next step, three numerical models were developed by using the PLAXIS-3D code based on the FEM. Then, a comparison was made between the experimental and numerical data to verify the outputs of the numerical analyses. In the procedure of numerical analyses, elastoplastic behaviors of embankment material and bed were defined based on the Mohr-Coulomb failure criterion, and micropiles were considered as linear elastic elements. Finally, after accomplishing a series of sensitivity analyses on the geometric parameters of micropiles, their efficiency factor was classified in the process of arrangement optimization.

In this study the relations between different chemical stabiliser solutions on the electrokinetic (EK) properties of tropical peat such as surface charge, diffuse double layer (DDL), current density, electroosmosis flow (EOF) and energy consumption are measured. The EK injection tests (with different chemical solutions) were performed with several electrolytes, namely, sodium silicate (Na2SiO3), calcium oxide (CaO), aluminium hydroxide (Al(OH)3) and calcium chloride (CaCl2) as chemical reagents. As a result, the suspensions with the high molarities of CaCl2, Al(OH)3 and CaO caused colloidal charge reversal in the surface of the colloidal from the negative to the positive. Furthermore, for the injection of NS-DW solution through the peat, electrokinetically, the total required energy was higher, about 693%, 373% and 234% for the EK injection of Al-DW, CaO-DW and Ca-DW, respectively. The same trend was also measured for the current density. After three days of EK tests, the current density for Al-DW, CaO-DW, Ca-DW and NS-DW was 0.267, 0.401, 0.668 and 1.872 mA/cm2, respectively. The results of this research can be used to evaluate an initial estimation for required energy to inject electrically and changing the flow net in a real elektrokinetic treatment.

The effectiveness of magnesium as a substitute material in enzyme-mediated calcite precipitation was evaluated. Magnesium sulfate was added to the injecting solution composed of urea, urease, and calcium chloride. The effect of the substitution on the amount of precipitated materials was evaluated through precipitation tests. X-ray powder diffraction and scanning electron microscopy analyses were conducted to examine the mineralogical morphology of the precipitated minerals and to determine the effect of magnesium on the composition of the precipitated materials. In addition to calcite, aragonite and gypsum were formed as the precipitated materials. The effect of the presence of aragonite and gypsum, in addition to calcite, as a soil-improvement technique was evaluated through unconfined compressive strength tests. Soil specimens were prepared in polyvinyl chloride cylinders and treated with concentration-controlled solutions, which produced calcite, aragonite, and gypsum. The mineralogical analysis revealed that the low and high concentrations of magnesium sulfate effectively promoted the formation of aragonite and gypsum, respectively. The injecting solutions which produced aragonite and calcite brought about a significant improvement in soil strength. The presence of the precipitated materials, comprising 10% of the soil mass within a treated sand, generated a strength of 0.6 MPa.

In oil-rich countries, contamination of soils with oil products can occur during the refining, transportation and operation processes. From a geotechnical viewpoint, oil contamination adversely affects the geomechanical be-haviour/properties. Also, depending on the circumstances, some fine soil deposits may have insufficient bearing capacity or undergo excessive settlement under loading. Both scenarios described typically require some form of ground improvement. Given their widespread application in various fields, the selective use of nanoparticles to improve the geotechnical properties can be a new approach. This paper presents an experimental study performed at bench scale on sandy lean clay (CL) soil with two main objectives: (i) to investigate the effect of increasing kerosene content on its constitutive behaviour/strength; (ii) to investigate the strength and stiffness improvements achieved for the clean and kerosene-contaminated soil using nanoclay and nanosilica materials as additives, both independently and together, including the effect of curing period. Significant and progressive reductions in strength and stiffness occurred for ≥8 wt% kerosene content. Significant gains in soil strength and stiffness were achieved for 0.5–2.5 wt% nanoparticle addition. For the clean CL soil, 1 wt% nanoclay or 1.5 wt% nanosilica addition produced the greatest improvement in strength. Compared with nanosilica, on the basis of its lower optimum wt% value required for both the clean and contaminated CL soil materials, the nanoclay material investigated was deemed more efficient in improving the uniaxial strength/stiffness.

This paper examines biocementation via the microbial-induced carbonate precipitation (MICP) process as an appropriate and promising new technology for stabilisation of loose sand and silty sand deposits as a method to mitigate wind erosion. The technique involves spray treating the sand surface layer with a mixture of cementation and bacterial-cell solutions, the ensuing reactions causing calcite precipitation to occur between the sand grains, thereby lightly cementing them together over time. The bench-scale experimental programme presented investigates the proposed technique's effectiveness for stabilisation of silica and carbonate sands with different gradations, determination of the optimal reagent concentrations, the time-dependent shear strength development for the crustal sand layer following single-and double-MICP spray treatments, as well as wind tunnel experiments. Of particular novelty were investigations of the effect of dew formation on crustal shear strength development with curing period and the efficiency of the MICP treatment for the outdoor environment compared to laboratory-controlled test conditions. The wind tunnel experiments demonstrated that 28-day cured singly MICP-spray-treated crustal sand layers were stable to simulated 20 m·s−1 winds measured at 20 cm above the layer surface.

Peat commonly occurs as extremely soft, wet, unconsolidated surface deposits that are integral parts of wetland systems. Cement is widely used for the stabilization of peat by deep mixing method. This paper presents the results of the shear strength parameters of study models (fibrous, hemic and sapric peats stabilized with columns formed by dry mixing method). The columns were formed of peat treated with cement in different proportions. Triaxial test was performed after curing the samples for 28 days to evaluate the shear strength parameters. The results showed that the shear strength of peats can be improved significantly by the installation of cement stabilized soil columns. The amount of cement used to form the column and its diameter were observed to influence the strain–stress graph of peat reinforced. Furthermore, the result showed that the effect of cement was the highest on sapric peat due to its physico-chemical properties.

Improving the engineering properties of soils is one of the common necessity encountered in geotechnical engineering applications. This article investigates the effect of the addition of polypropylene fiber (PPF) on shear strength parameters of compacted sand. Different percentages of PPF (0.5%, 1.0% and 1.5%) by dry weight of the sand were added. Maximum dry density (MDD) and optimum moisture content (OMC) of sand alone and PPF-reinforced sand were measured by standard Proctor compaction test. Subsequently, shear box test was applied for sand and PPF-reinforced sand under three different normal stresses, samples were prepared under the condition of OMC and MDD. The results showed that when the percentage of PPF reaches 1%, the internal friction angle was at maximum value and cohesion is at the minimum value. With increasing percentage of PPF internal friction angle decreased and cohesion increased.

This study evaluates the potential of improving an insitu calcite grouting technique. The grout is composed of an equimolar solution of urea– CaCl 2 and an enzyme named urease. We examine the distribution of the grout materials and precipitated calcite within sand columns with a diameter of 5 cm and a height of 100 cm. In the first series of experiments, the concentration distributions of the individual grout materials (i.e., urea, CaCl 2 and urease) within the sand specimen are evaluated. In the second series of experiments, an enzyme-reagent mixed solution (i.e., grout) is injected into the sand columns to evaluate the distribution of calcite. Sand samples are collected from various vertical locations within the treated columns and the amount of precipitated calcite is evaluated. Furthermore, attempts are made to achieve the uniform distribution of the injected grout and hence uniform calcite distribution throughout the specimen. The results show that a uniform distribution of the grout materials up to a distance of 1 m from the inlet is achievable. It is also observed that a relatively uniform distribution of calcite is achievable as long as the rate of calcite precipitation is well controlled.

Soft clay soil can be stabilized by the adding of small percentages, by weight, of sodium silicate, thereby producing an improved construction material and enhancing many of the engineering properties of the soil. In order to explain such improvements, one of the most frequently occurring minerals in clay deposits, namely, kaolinite was subjected to a series of tests. As sodium silicate stabilization is most often used in relation to construction, the tests were chosen with this in mind. As results, addition of 5mol/L sodium silicate showed the highest unconfined compressive strength (UCS) results. However the effect of chemical molarities on UCS become less and less, with longer curing time.

The construction of railway embankments on loose foundations using reinforcing elements results in improvement of the embankments' slope stability, which significantly reduces the amount of earthworks. In addition, reinforcement of foundation and embankment is essential to increase bearing capacity and minimise settlements. In this study, a preliminary numerical analysis was performed to design and set up a series of experimental tests for investigating the efficiency of micro piles in reinforcing the high railway embankments on loose foundation. To this end, two experimental models of embankment were explored: one without reinforcement and another reinforced with micro piles to stabilise the embankment slope. The minimised arrangement of micro piles to reinforce the experimental model was obtained according to the results of the preliminary numerical simulation using Plaxis-2D finite-element code. The experimental data included bearing capacity of the embankment, displacement of foundation and embankment and axial strain of the micro piles. Finally, the efficiency of micro piles in reinforcing high embankments on loose subgrades was assessed by comparing the experimental data of non-reinforced and reinforced embankments.

The US Department of Energy conducted two studies to estimate the potential of cellulosic biomass crops for production of biofuels on a national scale. However, limited long-term experimental information is available to support the resultant yield projections. The objectives of this research were: (i) to determine long-term (>10 years) biomass yields and soil impacts of switchgrass (Panicum vir-gatum L.), giant reed (Arundo donax L.) and mimosa (Albizia julibrissin Durazz.) in Alabama; and (ii) to establish relationships between precipitation and yields of these perennial biomass crops, and yields of cotton, maize, and soybean. Mimosa and giant reed received no fertilizer and were harvested once each year while switchgrass received 84 kg ha –1 of N fertilizer annually, and was harvested twice each year. Cotton, maize, and soybean were managed according to traditional practices for these crops in this region. Average annual biomass yields of mimosa, giant reed, and switchgrass were 40.1, 35.5 and 23.5 kg ha –1 over 16-, 11-and 22-year periods, respectively, with corresponding estimated annual N accumulation in aboveground biomass of 388, 372 and 163 kg ha –1. Yields of maize, cotton and soybean decreased sharply with decreasing precipitation, but there was no corresponding decrease in yield of the three perennial biomass crops. Changes in the yields of the biomass crops with age were also relatively small. Analysis of topsoil samples suggested considerably less removal of P, K, Ca, and Mg than was estimated from yield and concentrations of these elements in the biomass that was actually removed.

Cation binding by organic matter content (OMC) in soils has consequences for the behaviour of the organic compounds themselves, influencing adsorption, aggregation, and solubility, and thereby soil structure, translocation of organic matter within soils, and transport to waters. The study reported here involved a number of experiments using composition of alkaline earth metals grout to treat organic soils, in order to provide a better understanding of the engineering behaviour of this soil after stabilization. Besides, it provides a series of the laboratory mix design and testing which in turn provide an essential guide regarding the choice, dosage and economical amount of chemical binders. We carried out a series of batch test using composition of sodium silicate system binders to find their effects on physic-chemical properties of the organic soil. The results show that in the batch tests unconfined compressive strength (UCS), increases of up to 220% of the soil’s baseline strength can be achieved by adding the 3 mol/L Na2Sio3, while UCS results enhanced to 270% having an activator CaCl2 and/or Al2(SO4)3 additives. Moreover, using higher molarities of CaCl2 (for example, 1mol/L) did not show any remarkable effect on the UCS results.

This paper presents the results of triaxial tests conducted for the investigation of the influence of geotextile on both the stress–strain and volumetric change behavior of reinforced sands. Tests were carried out on loose sand. The experimental program includes drained compression tests on samples reinforced with different values of both geotextile layers (1 B Ng B 3) and confining pressure (r 0 c) varying from 50 to 200 kPa. Tests show that the contribution of geotextile is negligible until an axial strain threshold that range between 2.5% for a confining pressure of 50 kPa to lower than 1% for 100 and 200 kPa confining pressure. At higher values of e a , geotextile induces a quasi-linear increase in the stress deviator (q) and volume contraction in the reinforced sand. Tests show a negligible influence of the number of geotextile layers (Ng) on the contribution of geotextile to both stress–strain and volumetric change, when normalized with Ng. Tests also show that the contribution of geotextile to the stress–strain mobilization augments with the increase in the confining pressure, while its contribution to the volume contraction decreases with the increase in the confining pressure. The reinforced soil becomes contracting in the case of 2 and 3 geotextile layers.

The emphasis of current work is on assessing the settlement improvement ratio, which is described as the ratio between the settled soils treated with a stone column and the settlement of the non-treated soil (Sr = Streated/Suntreated). The research was conducted using a 300 mm diameter and 300 mm high stone-column container testing model. On 14 modeled stone columns made only from crush stones and using various backfill content, model tests including static axial compression tests were performed. The substance used in the stone backfill column had been changed by sand or lime or cement percentages. The shear strength prepared by the containers varied between 5.5 kPa and 13.5 kPa. Results show that the settlement ratio values, Sr achieved with crush stone, crushed stone +50% sand, crushed stone +5% dry lime, crushed stones +10% dry lime, crushed stone +2.5% cement +5.0% crushed stone +5.0% cement, respectively, was 0.23, 0.12, 0.16, 0.15 and 0.09. In other words, there is a drop in the settlement from 77% to 91%.

Soil reinforcement with natural and man-made fibers is one of the techniques to improve a number of mechanical and physical properties of soils. Although basalt originated fibers are currently being used for concrete, it is not an easy task to find a source in literature concerning the use of basalt fibers for soil improvement. In this study, basalt fibers have been used for this new aim. This study is an investigation into evaluation of the increase in soil strength, which is reinforced, in different percentages, by basalt chopped fibers. A silty soil sample has been chosen for this study and has been mixed, with 6, 12, and 24 mm long basalt fiber at varying contents. The unconsolidated undrained triaxial tests show that the addition of 24 mm long fibers into soil gives the maximum improvement in strength and the optimum fiber content (by dry weight of soil) is 1.5%.

The main purpose of this experimental study is to know the effect of improvement of soft soil by mixing it with granular materials on the properties of soft soil. The soil model was brought from a one construction project in Karbala, Iraq. Routine tests were carried out on the soft soil model alone, as well as for soft soil with specific percentage of granular materials. The model of cylindrical shape laboratory dimensions of 250 mm in diameter with a height of 300 mm. Eight different shear strength were used for laboratory model tests. Static loading tests were carried out on these model tests. It was found from results of model tests of improved soil that the averaged value of settlement reduction is 0.61 for all model tests, where the bearing capacity is increased by 31%.

This study concluded the results of a research on the features of cement based permeation grout, based on some important grout parameters, such as the rheological properties (yield stress and viscosity), coefficient of permeability to grout (kG) and the inject ability of cement grout (N and Nc assessment), which govern the performance of cement based permeation grouting in porous media. Due to the limited knowledge of these important grout parameters and other influencing factors (filtration pressure, rate and time of injection and the grout volume) used in the field work, the application of cement based permeation grouting is still largely a trial and error process in the current practice, especially in the local construction industry. It is seen possible to use simple formulas in order to select the injection parameters and to evaluate their inter-relationship, as well as to optimize injection spacing and times with respect to injection source dimensions and in-situ permeability. The validity of spherical and cylindrical flow model was not verified by any past research works covered in the literature review. Therefore, a theoretical investigation including grout flow models and significant grout parameters for the design of permeation grouting was conducted in this study. This two grout flow models were applied for three grout mixes prepared for w/c=0.75, w/c=1.00 and w/c=1.25 in this study. The relations between injection times, radius, pump pressure and flow rate for both flow models were investigated and the results were presented. Furthermore, in order to investigate these two flow model, some rheological properties of the grout mixes, particle size distribution of the cement used in this study and some geotechnical properties of the sand used in this work were defined and presented.

— This paper presents a study on the properties of soil stabilized by using lime and egg shell powder. Tests were conducted to assess the potential of egg shell powder in replacing lime, which can make the overall stabilization process economical and eco-friendly. Results obtained show that all the treated mixes gave much better strength than untreated soil. Egg shell powder was introduced in quantities of 0.5%, 1%, 1.5% and 2% of the weight of soil. Tests were conducted replacing up to 50% of the lime used for stabilization. It was observed that 25% replacement of lime by egg shell powder gave better strength properties and can be adopted for practical purposes.

This paper presents an innovative use of soil-cement mixing method using jet grouting technique to improve the bearing capacity of subbase foundation for road construction in Thailand. The construction sequences and the basic design example of jet grouting for embankment works on soft clay are also given in this paper. The design concept and method of analysis of jet grouting work using finite element technique, results of finite element analysis, the installation adopted and effectiveness of soil improvement system are given and discussed. It was found that the total settlement is reduced by the jet grouting. A case history at Pak Phanang Diversion Dam project, Nakornsrithamarat, Thailand is presented describing the engineering design and construction aspects of a successful project, which demonstrated the advantage of soil-cement mixing method over conventional pile driving for this site.

The existing soils in the nature that is used for construction cannot necessarily bear the loadings on the structure. For example, in granular soils, the natural soil may be very loose and show a lot of elastic settlement. Sometimes, there are soft layers, saturated clay and swelling soils at the lower depths, which may cause significant settlement in the structure in terms of foundation load and clay layer thickness. To avoid such settlements, it is necessary to use certain techniques to improve
the soil condition. One of the methods that have recently been widely used to reduce the settlement of soft soils and swelling soils is stone columns or single piles. In this research, first of all, the parameters in need for the analysis will be gained by using the experimental data, and then, the static and dynamic behavior of the confined stone columns is examined with geotextile and without geotextile by a group and single manner as in two-dimensional form using Plaxis numerical method of the finite element and the impact of the following parameters will be investigated in both static and dynamic modes: Column length, column diameter, single and group behavior of columns, and soil cohesion effect on the behavior of the confined stone column in geotextile and reduction of soil settlement during use of stone columns. The results of this research indicate correct understanding of the use of geotextile (Woven Geotextile with a specific elastic normal strength) to prevent the camber and the settlement of the column and increase of the strength and bearing capacity of the column.

The Geotechnical properties of adding crushed curbside-collected glass to Kaolinite S300 with various percentages of 10 to 50% were experimentally evaluated. Crushed glass passing the 2.36 mm (#8) sieve, and retaining on 1.18 mm (#16) selected for this study is collected from a different area in Johor Bahru, Malaysia. Measured hydraulic conductivities were on the order of 2.33E-6 and 1.87E-5 for 10% and 50% respectively. The result shows increment in the maximum dry density from 1.615 í µí±ší µí±” í µí±š 3 ⁄ at 10% to 1.908 í µí±ší µí±” í µí±š 3 ⁄ at 50% of addition of crushed glass with the optimum moisture content of 18.35% and 7.4% respectively. Friction angles from the direct shear test were evaluated between 12 to 25 degrees at normal stresses of 56.4 to 219.9 kPa. The result shows that the unconfined compression strength of Kaolinite S300 mixed with crushed glass is increased from 5.26 kPa at 10% addition of crushed glass up to 17.52 kPa at 50%. It can be concluded that the crushed glass is environmentally clean, readily available, and relatively low-cost material that can be one of the replacements for traditional aggregate to enhance the geotechnical properties of soft cohesive soils.

Construction of railway embankments on loose beds without using any methods of soil improvement (e.g. stone columns in silt and clay beds, deep soil mixing method, jet grouting and also using micropiles individually or in groups form) leads to reduction of embankment slope gradient, which significantly increases the volume of soil operation. Generally, micropile as a reinforcing element with the main characteristics of improving the mechanical-physical properties of soil, is a proper methodology for the aim of improving loose earth with low bearing capacity and intensive settlement characteristics. This paper explores numerical models of non-reinforced and reinforced railway embankments (with the height of 10 to 25 m) rested on loose beds that simulated and analyzed by SLIDE software. It should be considered that in order to reinforce the embankments using different arrangements of micropiles. In addition, the non-reinforced and reinforced embankments were analyzed against different load combinations that consist of railway operational load, permanent weight of the rail line and intense earthquake load. It should be mentioned that LM71 standard load was used as operational load during the simulations. The main purpose of this paper is finding the optimum arrangement of micropiles to reinforce the high railway embankments on loose beds. Therefore, according numerical analyses procedure, it was resulted that the use of micropiles exactly between toe and 1/3 to 1/2 length of the embankment slope is the optimal way to reinforce the embankments on loose beds.

En Colombia, en los últimos 15 años, se ha desarrollado un
proceso de investigación para la ampliación de la frontera
agrícola focalizado en la altillanura plana, con énfasis en
la construcción de capa arable asociado a la saturación de
bases, mediante el encalamiento, la labranza vertical y la
rotación arroz, maíz y soya, con la posibilidad de otras especies
como el algodón que podrían ingresar al modelo. Para
ello, se realizó una investigación pionera en Colombia para
determinar la adaptación del algodón en las condiciones de
las sabanas ácidas mejoradas de la altillanura. Se desarrolló
una prueba de evaluación agronómica con cinco genotipos
élites de algodón en un diseño de bloques completos al azar
en cuatro localidades en suelos con una saturación de bases
superior al 80 %. Los resultados permitieron identificar
un genotipo (LC-156), que presentó una adaptación a la
altillanura, asociado a un rendimiento promedio de 2,2 t/ha
de algodón semilla, 1,5 t/ha de algodón tipo fibra media
a larga y un porcentaje de extracción de fibra superior
al 36,0 %. La ventaja comparativa de esta región para una
producción sostenible de algodón está dado por el rendimiento
de algodón fibra superior al promedio nacional, reducción
del 33,2 % en los costos de producción, calidad de fibra
media larga con destino para la exportación y la ausencia
del insecto plaga de mayor importancia económica en
Colombia, el picudo (Anthonomus grandis Boheman).

improving soil parameters using dynamic compaction of was intensively studied by many researchers since 1980’s. Earlier researchers depended on statistical analysis of many case studies and soil dynamic principals to develop empirical formula used in designing dynamic compaction procedure. Recent researchers used different finite element models to describe the behavior of soil under dynamic compaction; those models varied between 1-D simple model and up to 3-D sophisticated ones. The aim of this research is to introduce a simple mathematical approach to simulate ground deformations and soil parameters improvement due to dynamic compaction. The proposed approach consists of two equations, the 1st one used to calculate the ground settlement due to one temper drop, the 2nd one used to calculate the updated soil parameters due to the ground settlement from the previous drop. By applying the two equations successively, both ground settlement and soil parameters improvement could be calculated after each tamper drop. The proposed approach was applied on four case studies and its results were so close to measured ones. The proposed approach could be used in designing or testing the dynamic compaction procedures and also in monitoring the quality of execution by comparing the measured settlement after each drop with calculated one.

Electrical resistivity is a non-destructive, cost-effective and sensitive method to evaluate soil's physical and chemical properties. Electrical resistivity has been used widely in surface and subsurface exploration. The electrical resistivity is directly related to the subsurface geotechnical and geothermal properties like porosity, temperature, salinity and water content. Recently uses of waste material as an additive to improve the soil engineering properties are growing because of their cost-effectiveness. Cement Kiln Dust (CKD) is a waste material of the cement manufacturing process. CKD is widely used as an additive material in ground improvement to improve soil's geotechnical properties. This study is mainly focused on the effect of CKD on the electrical resistivity properties of the soil. In this study, the electrical resistivity of a natural soil slope treated with CKD and a test model in the laboratory was investigated. Besides, the effects of CKD on soil pH and electrical resistivity were studied by performing a series of tests to predict the soil's corrosivity potential. The soil was treated with 0, 5, 10 and 15% of CKD and the electrical resistivity of the soil was measured at different water contents, porosities and curing times. The results indicate that the soil's electrical resistivity increases by increasing the CKD content and curing time. Additionally, an increase in water content or porosity decreases the electrical resistivity of CKD treated soil. Furthermore, the electrical resistivity measurement is a practical method to determine the stabilized soil's geotechnical and geomechanical properties.

The properties of soil play a major effect on the design of road pavements. Thus, using waste materials to develop the characteristics of weak soil is being progressively necessary for industrial constructions. In past years, several pieces of research have been done to show the significance of these waste materials on the strength of the soil. This research aims to focus on the impact of granite powder on the behavior of the soil subjected to loading. Therefore, soils blended with several amounts of granite powder i.e. 4%, 8%, 12%, 16%, and 20% of the total weight were examined. The CBR, compaction and direct shear tests were executed to evaluate the performance of the untreated and treated soils. The findings proved that adding granite dust increased noticeably the shear strength, CBR and dry density of the soils. It was found that an addition of 8% granite dust to the natural soil yields the most appropriate results among other contents of granite dust. Hence, it is concluded that the granite dust has good potential to be used as an additive for improving the engineering properties of clayey soil.

Liquefaction is one of the cardinal concern to the geotechnical engineers as well as those involved in the building and development of structural foundations. To strengthen the subsoil properties in terms of its bearing capacity, shear strength, and settlement; ground improvement techniques are often used. This paper reviews three ground improvement techniques suitable for remedial work near existing structures. Three techniques includes- compaction grouting, permeation grouting, and jet grouting. Suitable method can be selected according to loading conditions, characteristics of soil, project type and cost. The factors which influence the efficacy of a particular technique are identified. From the advantages and drawbacks stated, a combination of techniques may provide the most cost-effective ground improvement solution for preventing damage to existing lives resulting from liquefaction-induced settlement and uplift.

Studies of surface improvement have been carried out in Georgia-Poti in order to decrease surface deformations since surface conditions of railway line that comes from the harbor are too poor. Stone column and jet grouting methods were evaluated together as surface improvement methods. As engineering parameters on the surfaces which are applied, jet grouting are higher than the other method, it was decided to improve the line within project with this method. This study was carried out in order to present surface parameters obtained with seismic refraction data carried out together with surface improvement practices. Findings show that parameters of shear wave velocity, amplification rate and bearing power obtained with jet grouting practices are higher than those of stone column practices.

Soft soils such as clay soils, mostly if they comprise swelling minerals may produce great damage to structures, particularly when these soils are exposed to wetting and drying situations. The geotechnical properties of soft soils could be enhanced by utilizing chemical additives. In this paper, granite waste dust was used to adjust the properties of clay soils. This paper investigates the effect of granite rock dust on the geotechnical properties of soft soil. The particle size distribution, Atterberg limits, compaction, California bearing ratio (CBR) and direct shear strength characteristics of the soil when blended with various percentages of granite dust were evaluated. The findings show a great increase in the maximum dry density, optimum water content, direct shear strength and CBR with increasing the amount of granite dust. The best results obtained for CBR values were when the soils mixed with 8% granite dust. Although these findings indicate great improvement in the geotechnical parameters of clayey soils, the higher strength established is not enough for the enhanced soil to be utilized as a base material in the construction of heavily-trafficked flexible pavements. However, this modified material can be used as a base material for moderate traffic roads and as a sub-base material for high traffic roads.

The study was undertaken to assess organic fertilizer usage by garden egg farmers in Enugu State, Nigeria. The multistage sampling technique was used to select 80 garden egg farmers. Descriptive statistics and multiple regression analysis were used to analyse data for the study. The mean age of respondents was 39 years. Fifty-five percent (55 %) of respondents were married. The majority (97.5 %) of the respondents used farmyard manure while the average cost of organic fertilizer was N57372.73. A lesser percentage (7.5 %) of respondents in the study applied over 2000 kg of organic fertilizer per hectare with 40 % applying twice per season. The perceived benefit of organic fertilizer was: improvement of soil fertility (2.95 ± 1.12), environment-friendly (2.99 ± 1.23). A constraint identified in the use of organic fertilizer was: slow effect (2.12 ± 1.43), Odorous nature (2.06 ± 1.28) and difficulty in the collection and handling of organic fertilizer (2.72 ± 1.03). The study among other things recommends that farmers be granted credits and extension services that will teach them the required skills in the handling and use of organic fertilizer.

Shallow foundations are usually used for structures with light to moderate loads where the soil underneath can carry them. In some cases, soil strength and/or other properties are not adequate and require improvement using one of the ground improvement techniques. Stone column is one of the common improvement techniques in which a column of stone is installed vertically in clayey soils. Stone columns are usually used to increase soil strength and to accelerate soil consolidation by acting as vertical drains. Many researches have been done to estimate the behavior of the improved soil. However, none of them considered the effect of stone column geometry on the behavior of the circular footing. In this research, finite element models have been conducted to evaluate the behavior of a circular footing with different stone column configurations. Moreover, an Artificial Neural Network (ANN) model has been generated for predicting these effects. The results showed a reduction in the bending moment, the settlement, and the vertical stresses with the increment of the stone column length, while both the horizontal stress and the shear force were increased. ANN model showed a good relationship between the predicted and the calculated results.

Industrial waste is  one of the most important sources of environmental pollution in the world and Egypt. Providing economic  opportunities for recycling these  wastes represent  an  essential solution to this problem to  encourage waste producers to dispose  it safely  an d to provide an added value for these wastes.  This research  work will  study the feasibility of recycling certain industrial wastes for production low-cost building materials and improving the soil compaction characteristics . 
In this research work, the efficiency of  recycling some common local industrial wastes in production of construction materials was explored. The selected wastes include  cement kiln dust (i.e.  bypass) and
ceramics  powder.  Previous  researches  and  the  chemical  analysis  showed  that  both  wastes  are promising as cement replacement materials. However, this exploratory phase is an initial investigation
targeting the chemical  properties of theses wastes  for  efficient use of  both wastes to replace  cement –partially-  in mortar and plain concrete elements as well as bricks. The advantage of replacing part of
the cement content with  waste materials has double environmental action, by which reducing cement use leading to less carbon dioxide emission in addition to the safe recycling of the industrial wastes.
Based  on  the  selected  condition  of  the  cement  bypass  and  ceramic  powder,  no  significant enhancement  was  recorded  in  the  mortar  and  concrete  mixes  had  various  ratios  of  cement replacement. However, the main physical and mechanical  properties of some of the tested mixes provided  promising values for using these mixes for production of more green plain concrete, mortar and bricks.  For the soil enhancement application, addition of cement bypass to soil -commonly found in delta region -  increased the Calif ornia Bearing Ratio (CBR) value of this  soil by 300%. Currently more comprehensive investigation is running to cover more than cement and ceramic factories in order to have a reliable data base of the properties of these types of industrial wastes and the  efficient recycling of these wastes in construction materials and soil improvement applications.

Soil plays an important role in any structure, so soil improvement has become one of the most essential parts of construction projects. This study investigated influence of  sawdust admixture on inshore sandy soil stabilized by zeolite and urease enzyme. One of the problems that environmental engineers encounter with is accumulating waste materials، sawdust is one of these materials. One way for reducing these side products is reusing them, especially for soil improvement. Sandy soil with uniform granulation (SP) due to it’s incoherence is one of the most problematic kind of soils. Therefore, sawdust with zeolite has been used to improve soil engineering properties and the results have been compared with the effect of calcium carbonate precipitation (CaCO3) on the soil. Today, by advancement in various sciences and knowledge boundaries elimination in various fields, new and environmentally friendly materials can be used as an alternative method to traditional materials. One of these substances is urease enzymes, which are obtained from natural sources such as Jack Beans  or bacteria’s activity  such as Sporosarcina pasteurii. Samples in this study were made with  4, 8 and 12 percent by weight of zeolite and 4, 8 and 12 percent by weight of sawdust and were cured for 7, 14, 28 and 45 days. According to compaction test results, by increasing zeolite and sawdust’s percentage, optimum moisture content has been increased and maximum dry density decreased. The results of unconfined compression strength (UCS) test showed that the samples with 4% sawdust, 8% zeolite and calcite precipitation has about 9% increase in maximum strength compare with the samples without calcite precipitation and with higher zeolite content. Also, the rupture strain of samples with calcite precipitation was higher than the samples without it.

Strengthening beach sand using enzyme induced carbonate precipitation (EICP) was demonstrated. Enzyme induced carbonate precipitation (EICP) is an emerging biologicallybased ground improvement technique that precipitates calcium carbonate within the pores of a granular soil via hydrolysis of urea catalyzed by free urease enzyme. In this study, samples of a natural beach sand were treated using an EICP solution at one, two, and three cycles of treatment (one pore volume per treatment cycle). Strength and carbonate content of the treated specimens were measured using unconfined compressive strength (UCS) testing and acid digestion. X-ray diffraction analysis and scanning electron microscopy (SEM) were used to evaluate the morphology of the precipitates. The treated specimens showed average UCS of 145 kPa, 241 kPa, and 483 kPa at average carbonate content of 1.96%, 2.98%, and 3.69% (corresponding to one, two, and three cycles), respectively. Calcite was observed to be the main crystal phase in the treated specimens.

Soil is naturally heterogeneous and non-uniform materials because it is made up of different types of matter. Understanding of soil parameters is one of the most complex tasks in geotechnical engineering. Several laboratory tests of soil have to carry out for engineering practices. Laboratory tests take too much time to accomplish and extravagant also. There is another alternative way to get soil parameters direct from soil field investigation report to save time and cost. The main objective of this study is to investigate the relationships of soil parameters with most commonly used soil investigating tools SPT and CPT. In this research, three pairs of CPT and SPT tests were performed at the riverbank of the Rupsha River, Khulna, Bangladesh. Different correlations have been developed in this paper among various field tests and laboratory tests. Analysis demonstrate that q tc /N 1-60 ratio as a function of constant are better applicable to the local soils instead of D 50 or f c based correlations. Finally, Internal angel of friction (ϕ) has been carried out using the correlation of SPT, CPT and compare with internal friction angle (ϕ) from Direct Shear (DS), and Multi-Stage Triaxial tests (MSTT) have been performed.

Improvement of the Geotechnical properties of expansive soils by mixing Lime and Polypropylene Fibers is the main concentration of this research. For this research purpose, expansive soil samples were collected from the NorthEast part of Dhaka. The soil has been proved to be expansive (Plasticity Index, Plastic Limit, Liquid Limit, Swelling Pressure, Swell Index, and Swelling Potential). In this study, polypropylene fibers and lime were used with soil to observe its effect on the strength and swelling properties of expansive soil. The soil sample was formulated with 2.5% to 10% lime by the weight of soil and 2% polypropylene fiber was mixed with soil. Compared with the raw sample with swelling properties of the stabilized samples decreases in the beginning when lime content up to 7.5%, then it increased. Polypropylene fiber was used to reduce the axial and lateral expansion of this soil. The results show that the untrained shear strength and unconfined compressive strength of improved samples with the addition of lime and fiber concentration is substantially higher than the unimproved samples. Whereas, axial compression decreases finally, it may be said that the stabilization of expansive soils with lime and polypropylene fiber could be a practicable method.

Organic soil is a kind of soil that contains organic matter. Soil organic matter (SOM) is that kind of organic matter of soil, which consists of different ingredients such as plants, animal residues, cells and tissues of soil etc. at various stages of decomposition. Normally organic soils are rich in water content with high porosity and therefore successful stabilization has to depend on the type and amount of binder added. The commonly used binders are lime, fly ash and cement. This study reveals the variation of behavior of organic soil-lime, organic soil-fly ash and organic soil-cement mixtures at an amount of 5%, 10%, 15% and 20 %. The maximum shear stress and maximum angle of friction were found for 10% cement mixed with soil.