Department of Geotechnics and Roads

This paper presents results of undrained and unconsolidated (UU) triaxial tests related to the influence of tire waste addition on strength characteristics of red clay from Patoka in Southern Poland. Angle of internal friction and cohesion values were estimated for 30 specimens prepared from pure red clay (RC), its mixtures with two different fractions of shredded rubber in 5%, 10%, and 25% mass proportions as well as for pure powder (P) and granulate (G). It has been observed that the addition of granulate contributes more to the increase in the angle of friction than the addition of powder (uu = +1% (G-5) / +16% (G-10) / +31% (G-25), uu = +1% (P-5) / +10% (P-10) / +19% (P-25)). On the other hand, rubber additions reduce cohesion in mixtures, and the effect is enhanced with increases in their grain size and percentage composition (cuu = −31% (G-5) / −63% (G-10) / −87% (G-25), cuu = −67% (P-5) / −58% (P-10) / −58% (P-25)). It has been noticed that a change of parameters uu and cuu causes a decline of shear stresses at increasing granulate content. There is an inverse relationship for powder. At the same time, it has been shown that the failure strain, hence a change in red clay-rubber (RCR) mixtures plasticity, is related to the level of confining stress 3 and the type of rubber waste. Results of tests and their comparison with results of other researchers show that each time it is necessary to experimentally verify a given soil with specific rubber waste.

This paper presents results of undrained and unconsolidated (UU) triaxial tests related to the influence of tire waste addition on strength characteristics of red clay from Patoka in Southern Poland. Angle of internal friction and cohesion values were estimated for 30 specimens prepared from pure red clay (RC), its mixtures with two different fractions of shredded rubber in 5%, 10%, and 25% mass proportions as well as for pure powder (P) and granulate (G). It has been observed that the addition of granulate contributes more to the increase in the angle of friction than the addition of powder (uu = +1% (G-5) / +16% (G-10) / +31% (G-25), uu = +1% (P-5) / +10% (P-10) / +19% (P-25)). On the other hand, rubber additions reduce cohesion in mixtures, and the effect is enhanced with increases in their grain size and percentage composition (cuu = −31% (G-5) / −63% (G-10) / −87% (G-25), cuu = −67% (P-5) / −58% (P-10) / −58% (P-25)). It has been noticed that a change of parameters uu and cuu causes a decline of shear stresses at increasing granulate content. There is an inverse relationship for powder. At the same time, it has been shown that the failure strain, hence a change in red clay-rubber (RCR) mixtures plasticity, is related to the level of confining stress 3 and the type of rubber waste. Results of tests and their comparison with results of other researchers show that each time it is necessary to experimentally verify a given soil with specific rubber waste.

This paper is a continuation of the paper “Triaxial tests on weak cohesive soils – some practical remarks (part 1)” and concerns
the problems related to the preparation of weak cohesive soils for triaxial testing. This part (2/2) presents detailed
description and discussion of the issues related to installation of specimen in the apparatus and assembling various accessories before the main test. It is based on the Authors’ own experience and literature review. Some solutions, which make the work with weak soils easier and, at the same time, increase the reliability of the results, are suggested e.g.: the paraffin method or the use of a special frame enabling repositioning of local microdisplacement sensors during the triaxial test. The issues connected with soil sampling and forming of triaxial specimens have been included in part 1/2 of this article. In the Authors opinion, the text (parts 1 and 2) may constitute an important hint for researchers completing a triaxial testing station
intended for testing weak cohesive soils.

Standard procedures of triaxial testing recommended e.g. in Eurocode 7 are often unsatisfactory in case of weak cohesive
soils (soft and very soft clays, clayey soils with organic content, etc.), mainly due to the high deformability of these soils.
Forming a specimen from material sampled in situ and installation of the necessary equipment (a membrane, filter paper
strips or on-sample sensors, etc.) may be very difficult and can influence the quality of the test results. This paper (part 1/2) presents detailed description and discussion of the issues related to weak soil sampling and forming of triaxial specimens, based on the Authors’ own experience and literature review. Some solutions, which make the work with weak soils easier and, at the same time, increase the reliability of the results, are suggested e.g.: an “extra consolidation” in a sampler or alternative preparation of the specimen from slurry. Due to the ampleness of the problems related to testing of weak cohesive soils, another issues, such as installation of a triaxial specimen in a chamber or equipping it with different accessories, have been described in part 2 of this paper. In the Authors opinion, the text (parts 1 and 2) may constitute an important hint for researchers completing a triaxial testing system designated for testing weak cohesive soils.

The paper is the second part of the description of an interdisciplinary research concerning the modernization of laboratories at the Faculty of Civil Engineering, The Silesian University of Technology. This paper was focused on the conditions concerning the specific nature of laboratory works involving geotechnics and the methodology of pre-design studies performed in stages. The recapitulation contained the conclusions and a presentation of design solutions based on the conducted research. This text constitutes a continuation of the paper: ERGONOMICS OF LABORATORY ROOMS – CASE STUDIES BASED ON THE GEOTECHNICAL LABORATORIES AT THE SILESIAN UNIVERSITY OF TECHNOLOGY.