Vol 56, No 4 (2019)

We present a procedure for the evaluation of the rational volumes of soil solidification in the shorings of deep foundation pits higher and lower than the bottom of the pit with an aim to decrease the horizontal pressure of soil upon the shoring and to enhance the resistance of soil to the horizontal displacements of the restraining structure. The problem is solved by using a two-stage iterative scheme with regard for the condition of minimal volume of solidification, which guarantees the variations of displacements at the top of the restraining structure within the admissible limits.

We analyze the existing methods aimed at the evaluation of settlements of the buildings and structures and propose a modulus-free method for the evaluation of settlements of the foundations, which enables us to take into account local variations of the compressibility and stressed sate of the soils of foundations caused by the natural and anthropogenic factors. The application of the proposed procedure for the evaluation of additional settlements of the foundations of heightened buildings revealed its acceptable reliability confirmed by the results of theoretical and experimental investigations.

Results are presented of test studies of the compressibility of pebble-gravel soils in triaxial compression instruments that make it possible, by contrast with uniaxial compression instruments, to estimate the strain anisotropy of soil. The dependence of the coefficient of strain anisotropy on the acting stress is presented.

Consolidated quick direct shear tests were conducted on bentonite and mixed bentonitekaolin soils with different concentrations of sodium chloride solution. The physical mechanism of the pore fluid concentration effect was explained at the micro level on the basis of micro forces among particles. The test results indicated that the shear strength of bentonite and bentonite-kaolin noticeably varied with increase in sodium chloride solution concentration, especially under high vertical stress. The friction angle increased with the pore fluid concentration, but the cohesion decreased. With increase in pore fluid concentration, the electric double-layer repulsion among soil particles decreased, thereby increasing the effective contact stress at the mineral-mineral contact and leading to increased consolidation settlement and a lower water content under vertical stress. This means a larger shearing resistance at the mineral-mineral contact point and a thinner absorbed water layer at the mineral-water-mineral contact point, leading to a greater friction angle and a lower cohesion.

The results of a model study of single piles shaft bearing capacity in dry and saturated sandy soils are presented. The effect of loading rate on pile shaft capacity was investigated. The shaft bearing capacities of the piles were determined by pile load tests and compared with theoretical results. Generally, pile shaft capacities are greater than the theoretical values. The lateral earth pressure coefficient K depends on the internal friction angle of the soil, the pile diameter, the effective stress, and the saturation degree of the soil. It is shown that K decreases as the pile length/ diameter ratio increases.

A theoretical approach is proposed to investigate blast-induced ground vibration by considering the body force. On the basis of the principle of momentum conservation at the wavefronts, we derived the reflected body waves along the ground surface and the interaction of the body wavefront and ground surface inducing the secondary surface wave that transfers outward onto the ground. Subsequently, the particle velocity on the ground surface was derived, and a parametric investigation was conducted with regard to the effects of horizontal distance from the blast source, embedded depth of the blast source, and material damping onto the ground vibration. Finally, the effect of gravity on the ground vibration was also investigated.