Soil reinforcement through the inclusion of oriented or randomly distributed discrete elements such as fibres has recently attracted increasing attention in geotechnical engineering. Therefore, the purpose of this paper is to investigate the influence of certain parameters (the strength properties of the fibre, the relative size of the fibres and grains, and the rate of shear) on the shear strength of polypropylene fibre reinforced cohesive soils. A series of consolidated drained or undrained direct shear tests were conducted on unreinforced and reinforced sandy silt and silty clay specimens. Two types of polypropylene fibres with different mechanical indices were used. The fibre content was varied between 0.3% and 1.1% by weight of dry soil. The test results revealed that the inclusion of fibres in soil significantly increases the shear strength. The attainment of the high shear strength is attributed to the micromechanisms involved in the fibre/soil interactions as studied through scanning electron micrographs. The results also showed that the reinforcement effect was more pronounced under undrained shearing conditions. An important outcome from the current work is that, from the data obtained, the strength of the reinforced soil composites is not practically affected by the fibre mechanical indices.

The use of new materials for soil strengthening is crucial for geotechnical engineering, especially in foundation construction. Our main objective was to investigate the potential use of two-component water soluble epoxy resins to improve the physical and mechanical properties of medium sand, because the efficacy of these resins on soil strengthening has not yet been properly investigated. Experiments were conducted using resins with different epoxy resin-to-water (ER/W) ratios. The results indicate that the epoxy resins improve the physical and mechanical properties of sand significantly, and if successfully grouted into a formation, the resins could provide a suitable solution for the stabilization of foundation material. Based on the experimental results, a nonlinear regression analysis was performed to correlate the mechanical properties and permeability with curing time and ER/W ratio.

The use of additives to improve the quality of cement grouts is crucial for civil engineering, especially in foundation construction. This article presents experimental data concerning the compressive strength, elastic modulus, bleeding and injectability of microfine cement grouts modified with epoxy and acrylic resin emulsions. Strength properties were obtained at different curing ages. For further analysis and detailed discussion of properties of polymer-modified cement grouts, see "Fundamental properties of epoxy resin-modified cement grouts" (C.A. Anagnostopoulos, G. Sapidis, E. Papastergiadis, 2016) [1].

High-range water reducers, such as superplasticisers, can be potentially viable for cement grouting applications. In this study, we investigate the influence of two types of superplasticisers-one based on polycarboxylate ether and another based on naphthalene condensates-on the injectability of thick cement grouts into coarse soil and on the shear strength parameters of the grouted soil. Injectability tests were performed on soil columns with various superplasticiser dosages and grouts prepared with different water-to-cement ratios over a wide range of grouting pressures. The shear strength parameters of the grouted soil were evaluated through undrained unconsolidated triaxial compression tests.