Soil Mechanics and Foundation Engineering最新文献

In this research, the swelling pressure tests under different conditions were carried out on the Nanning grey-white expansive soil. The effects of dry density, initial moisture content and external load on the swelling pressure were investigated. The test results indicate that both lateral swelling pressures are essentially the same, but the vertical swelling pressure is higher than the lateral swelling pressures. For the same dry density, the vertical swelling pressure decreases with the rise in the initial moisture content, while for the same initial moisture content, the vertical swelling pressure increases with the rise in dry density. The lateral swelling pressure increases with the increase in the overlying load. When the lateral swelling pressure decreases, the sliding stability coefficient and overturning stability coefficient of the retaining wall are increased from 0.60 and 1.15 to 1.30 and 1.81, respectively.

Examples are given of the reconstruction of the bases and foundations of buildings and structures of the Moscow Kremlin and the Novodevichy Convent, as well as the construction of the Patriarch Germogen Monument in the Aleksandrov Gardens. The scientific support work is described, including geotechnical modeling, development of protective measures, and monitoring programs for geotechnical and heat-humidity conditions.

Compared with conventional soft clay ground treatment methods, electroosmosis has many advantages, such as a fast drainage rate and convenient equipment installation. However, its practical applications encounter restrictive factors, such as severe electrode corrosion and high energy consumption. As a flexible electric geotextile, carbon fiber cloth has good electrical conductivity and durability and excellent electrical contact performance with the soil. In this paper, carbon fiber cloth was used as the electrode material, and electroosmosis combined with the chemical grouting method was used in laboratory model tests. The electroosmotic characteristics and electrode-soil interface characteristics of carbon fiber cloth electrodes were discussed, and the influence of chemical grouting on these characteristics was considered. The results indicate that injection of CaCl₂ and Na₂SiO₃ solution reduced the soil resistance and electrode-soil contact resistance but reduced the electroosmotic drainage rate and increased the energy consumption coefficient. The electrode-soil contact resistance of the carbon fiber cloth electrode was less than that of the stainless steel electrode and had a higher efficiency of electric energy utilization when injected with chemical solution.

Laboratory soil testing is the main method used to set the parameters of nonlinear constitutive models. However, the sample quality may be too poor to reflect the mechanical behavior of the real soil massif correctly. Additional calibration of the model input parameters based on field test data leads to a more accurate approximation of soil behavior. In this study, methods for automated calibration of input parameters of nonlinear constitutive soil models are proposed. The calculated stress-strain curve for the examined examples showed high convergence with the real one, which proves the correctness and effectiveness of the methodology.

As a common soil-improvement method, cement-stabilized soil is widely utilized in ground treatment and resource utilization of in-situ muds. The unconfined compressive strength (UCS) and strength recovery of a remolded cement soil were studied. The test results show that the UCS values of remolded cement soil are significantly lower than those of the corresponding undamaged cement-stabilized soil. The strength loss of remolded cement soil is influenced by cement content and curing age; difference in remolding time has little effect for the same total curing age. On the basis of the test results, a formula to predict UCS for remolded cement soil is proposed. The microscopic mechanism of the strength change of remolded cement soil was analyzed by scanning electron microscopy. The particle spacing of remolded cement soil was closer than that of cement-stabilized soil, but the adhesiveness of hydration products was reduced, which weakened its structure.

Multi-underreamed anchors (MUAs) are widely used in areas with soft soils owing to their high ultimate capacity. To explore the bearing mechanism of MUAs in soft soil, this paper performs a model test of MUAs in silty clay and draws the following conclusions. With an increase in the underream number of MUAs, the ultimate capacity of the anchors significantly increases. The strength of MUAs develops faster and more efficiently than that of non-underreamed anchors but is lost faster after the load reaches its peak value. There are two failure modes of MUAs, namely arch-shaped and cylindrical failure modes. Both of them involve three processes: initial cracking, crack deflection, and crack penetration. The ultimate capacity of ground anchors is composed of end and side bearing capacity. For MUAs, both the side and end resistance effects are improved. Owing to the superposition of the two kinds of effects, the ultimate capacity of MUAs is higher than that of non-underreamed anchors.

The instantaneous strong load generated by an explosion outside of a subway tunnel can destabilize and damage the tunnel’s lining, and thus endanger human safety and property. To avoid this risk, it is necessary to investigate the dynamic response and damage of subway tunnels under explosion-induced loads. This study used the ANSYS/LS-DYNA software to establish the finite element model of a tunnel. The surface side blast angle, tunnel buried depth, and explosive equivalent were the considered variables, and the dynamic response and damage of the tunnel’s lining structure under an external blast-related load were analyzed. The results reveal that, when the side blasting angle was 15°, the tensile strain was 150 on the left side, which means that the horizontal deformation of the lining cannot be ignored. When the buried depth of the tunnel was used as the main variable, the damping effect of the soil medium was obtained by comparing the displacement–time and velocity–time data. This comparison provides a reference for reasonably setting the tunnel depth in similar projects. When the explosive equivalent was considered as the main variable, the overall instability caused by the local damage of the lining structure was analyzed. The findings of this study can be used to improve the design of effective countermeasures and systems for protecting tunnels from external explosions, and have high technical, economic, and social importance and reference value for similar engineering design projects.

Expansive soil is mainly composed of hydrophilic minerals, and shows significant deformation characteristics after watering, which often causes great harm to engineering construction. In this study, numerical analyses were conducted to investigate the effects of anti-sliding piles on the deformation mechanisms of a bridge foundation in an expansive soil slope. It was found that deformation of the bridge foundation was affected not only by rainfall-induced swelling of expansive soil, decrease in strength, and sliding force, but also by indirect effects of anti-slide pile resistance and space constraints. Anti-slide piles on expansive soil slopes were likely to exacerbate the effect of slope deformation and/or landslides on the bridge foundation. When the distance from the bridge foundation was large, the effect of the anti-sliding piles on the bridge foundation was small; otherwise, the effect was large.

The building technology on permafrost foundations using a heat-insulating pad made of granulated foam-glass ceramic is considered. The influence of the pad on the temperature regime of the frozen base of a dome-type residential building was studied using computer modeling. The design parameters of the insulating pad were established to ensure the thermal stabilization of the frozen base for 30 years. A technical and economic assessment of the new technology is given, taking into account the production of thermal insulation based on Arctic raw materials: opal-cristobalite rocks and zeolites.

An approximate solution to the problem of the bearing capacity of a two-layer soil base under an inclined load is given. To assess the bearing capacity, the coefficient of influence of the underlying layer is introduced. The logarithmic spiral method is used to determine this coefficient.