Soil Mechanics and Foundation Engineering最新文献

Similar materials were used to make quasi-sandstone with parallel double fractures, and the process of freezing inclined shaft construction was reproduced through indoor freeze–thaw tests. The basic physical parameters of double fractured quasi-sandstone before and after thawing were measured, and indoor triaxial compression tests of double fractured quasi-sandstone with different dip angles after thawing were carried out. The influence of fracture dip angle on the mechanical properties and failure characteristics of the quasi-sandstone was analyzed. The results show the following. The double fractured quasi-sandstone had strong water absorption, and there were different degrees of freeze–thaw damage. Under triaxial compression, with the increase of fracture dip angle, the peak strength of the quasi-sandstone first increased and then decreased, and it was the minimum when the fracture dip angle was 30°. The energy evolution law was similar for different crack dip angles. In the elastic stage, the growth rate of elastic energy was greater than that of dissipated energy, whereas in the plastic stage, the dissipated energy gradually increased and exceeded the elastic performance. When the crack dip angle was 90°, the increase in the growth rate of dissipated energy was most significant. In addition, there were three main failure modes of quasi-sandstone under triaxial loading: when the dip angle of the fracture was 0°, wing crack propagation occurred in the rock, causing rock bridge failure. When the fracture dip angle was 30° or 60°, the rock was sheared. When the fracture dip angle was 90°, the rock was tensioned.

Owing to the advantages of easy installation, low cost, and high bearing capacity (P), torpedo anchors (TAs) are suitable for anchoring the floating platforms used in deep-sea oil exploitation. This study investigated the P of conventional and end-bearing TAs in saturated, normally consolidated soils based on a numerical calculation using the ABAQUS software. According to numerical calculations with different parameter values, the effects of factors such as the location, area (S), embedment depth (h), and pullout angle (α) of the bearing plates on P were investigated. Based on the numerical calculation results, vertical (V)–horizontal (H) envelopes for the P of TAs were established. The results reveal that the P of a conventional TA under vertical pullout loading between numerical calculation and American Petroleum Institute (API) standard exist a difference of only 3%, which confirms the reliability of the numerical model. The P of the end-bearing TAs was significantly higher than that of conventional TAs, and the TA equipped with bearing plates at the bottom had a relatively high P, which increased significantly as S and h increased. When S exceeded a certain value, P increased with α. An increase in S resulted in an increase in the envelope coefficient A and a decrease in the envelope coefficient B, and caused the envelope to protrude outward. Establishing V–H envelopes has a certain reference value for estimating the P of TAs in actual engineering.

Tailings dam accidents can result in serious casualties and environmental problems. Therefore, it is necessary to analyze the factors affecting the safety of tailings dams. In this paper, the permeability characteristics of sedimentary fine tailings, including the degree of compaction, and the seepage failure of tailings dams are explored. The results indicate that the permeability coefficient gradually decreases with increasing fine-particle content. There is a threshold associated with the fine-particle content at which the trend in the coefficient changes. The fine-particle content at this threshold is 35% for particles finer than 0.075 mm and 15% and 30% for particles finer than 0.005 mm. At a given fine-particle content, the permeability coefficient of horizontal sampling tailings is the largest, followed by that of uniform tailings, with the permeability coefficient of vertical sampling tailings being the smallest. When low pressure is applied to tailings containing fewer fine particles, even though the pores are reduced in size, they are still connected. Only under high-pressure conditions can the connectivity of the pores of tailings containing few fine particles be reduced. When the fine-particle content increases, the fine particles fill the spaces between the coarse particles. Low-pressure conditions can then reduce the connectivity of the pores.

The degree of salinity, the freezing point, and the amount of unfrozen water are key factors in predicting the temperature, humidity, and mechanical behavior of saline permafrost soils used in construction as foundations for buildings. The results of the experimental studies are presented and a method for calculation of the amount of unfrozen water in saline soils is proposed. The calculated and experimental data show good convergence for both sandy and clay soils of different salinity and water content.

To reduce the influence of unfrozen water content and thermal parameter variations caused by freeze–thaw cycles on temperature field predictions, the water content of unfrozen sand and clay was measured during freeze and thaw. The specific heat capacity, apparent specific heat capacity, and thermal conductivity of frozen soil were calculated using the mass-weighted average, equivalent latent heat, and geometric average methods, respectively. On this basis, the hysteresis behaviors of unfrozen water content and the variations of thermal parameters of frozen soil with temperature and temperature pathways were analyzed.

An experience in the design and construction of a combined footing for a high-rise building in the presence of underground excavations at its basement is presented. A brief review of the construction conditions is presented. Prediction calculations of settlements and the results of their monitoring during the construction process are analyzed. The calculated and actual characteristics of the foundation deformability are compared.

An engineering method for single-bored pile settlement prediction considering the elastic–plastic behavior of soils is proposed. The method is based on the Botkin–Kondner hyperbolic model. The comparison of the engineering method and bored long pile load test results in overconsolidated soil is presented. The single-pile settlement prediction taking into account the nonlinear behavior of soils is more accurate. The friction reduction coefficient of the pile shaft resistance in overconsolidated soil has been refined.

Pile foundations may be subjected to a combination of vertical and lateral loads that are commonly not applied simultaneously. Model tests of six instrumented single piles embedded in remolded loess, in which self-developed equipment was used to carry out different loading sequences of vertical and lateral loads, were performed. The test results indicate that the preapplied lateral load can cause a decrease in the average skin friction of the pile shaft within 13 times the pile diameter below the ground surface, as well as an increase in the pile end resistance. The settlement of the pile top increases with the increase in the preapplied lateral load, and its rate of change increases with increasing vertical load and increasing preapplied lateral load. With the increase in the preapplied vertical load, both the horizontal displacement of the pile at the measuring point and the maximum bending moment of the pile shaft decrease. The location of the maximum bending moment of the pile shaft is between 2 and 4 times the pile diameter below the ground surface, which approaches the ground surface when the preapplied vertical load increases. The preapplied vertical load can increase the ultimate horizontal bearing capacity of the pile.

To investigate the folding-down mechanism of the shear strength parameters under the disintegration of carbonaceous rock slopes, carbonaceous rock shear strength tests under different disintegration times were conducted, and the principle of carbonaceous rock disintegration was elucidated through microscopic analysis. The reduced relationship between c and φ was derived with consideration to the degree of disintegration, and an early warning displacement inflection point method considering the maximum slope displacement and plastic shear strain is proposed as the slope instability criterion. Numerical examples demonstrate that the proposed method fully considers the attenuation law of the strength parameters of carbonaceous rocks in the calculation, and effectively solves the difficult problem of determining the reduction relationship using the double reduction coefficient method.

This study analyzed the mechanism of a new interlock-enhanced integral geocell (IEI geocell)-reinforced foundation using FEM3D. The vertical displacement, horizontal displacement, and stress distribution in the soil were studied. The tensile stress, friction, and contact force of the IEI geocell strips were also investigated. The IEI geocell reinforcement layer was found to reduce the horizontal and vertical displacements. The confinement of the IEI geocell is mainly attributable to friction between the infill material and the IEI geocell wall. The stiffness of the IEI geocell offers a tensioned membrane effect and broader stress distribution, resulting in better performance of the soil foundation.