Simplified Calculation Method for Seismic Active Earth Pressure of Translational Retaining Wall considering Soil Arching Effect

At present, most seismic earth pressure theories have the limitations of complex derivation process and difficult solution. To solve these problems, considering the deflection of small principal stress caused by soil arching effect, the central arc soil arch was approximated to two inclined linear soil arches, which can greatly simplify the derivation process. Firstly, by improving the combination of differential thin-layer element method and pseudostatic method, the theoretical formulas of seismic active earth pressure intensity, resultant force size, and resultant force action point under translation mode (T mode) were derived and were verified by experimental results. Then, the influence of soil internal friction angle, wall-soil friction angle, and seismic coefficient on seismic active earth pressure theory was analyzed. The results show that the seismic active earth pressure is nonlinearly distributed, and the seismic horizontal coefficient has a greater influence than other influence factors. The theoretical results can provide reference for the seismic design of retaining wall.

Soil Arching of Piled Embankment in Equal Settlement Pattern: A Discrete Element Analysis

Soil arching, which occurs in the piled embankments, plays an important role in stress redistribution between the relatively soft subsoil and the stiffer piles. The formation of the soil arching depends on the differential settlement of the embankment fill above the pile and the subsoil. The soil arching effect is barely investigated in the literature from the perspective of differential settlement of piles and soils. Based on the discrete element method (DEM), this paper develops a classic trapdoor test model to investigate the differential settlement in piled embankment during the downward movement of the trapdoor, and to explore the formation mechanism of soil arching in equal settlement pattern by changing the width of the pile cap and the height of the embankment. Due to symmetry, only one section of the laboratory test model is simulated herein. It was found that the soil arching formed under the equal settlement pattern remained unchanged after a certain degree of development, and the height of the equal settlement did not change at 0.7(s-a), where s is the pile spacing, and a is the width of the pile cap. The height of the embankment (H) and the width of the pile cap (a) have a significant influence on the formation of the equal settlement pattern when the width of the trapdoor is kept constant. Both the decrease in “H” and the increase in “a” facilitate the differential settlement of the soil between the piles and the pile-soil, enabling the slip surface to develop upward gradually, thereby hindering the formation of the equal settlement pattern.

Numerical Simulation of Stress Arching Effect in Horizontally Layered Jointed Rock Mass

Stress arching effect during the excavation of broken surrounding rock in underground engineering has an important influence on the stability of surrounding rock after underground excavation. To determine the stress arching effect in horizontally layered jointed rock mass, the stress arching characteristics of surrounding rock mass after excavation is analyzed in this study by using a series of numerical tests. The formation mechanism of stress arch is revealed through a comparison of the stress characteristics of a voussoir beam structure and theoretical analysis of multi-block mechanical relationship of jointed rock mass. The method for determining the boundaries of a stress arching zone is proposed, and the influence of various factors on a stress arch is further discussed. Results show that after the excavation of horizontally layered jointed rock mass, the stress arch bunch (SAB) is formed in the lower strata above the cavern, and the global stress arch (GSA) is formed in the higher strata, both of which are symmetrical arch stress patterns. The SAB is the mechanical manifestation of the voussoir beam structure formed by several low-level sandstone layers, and the GSA is caused by the uneven displacement between blocks. Compared with the GSA, the SAB is more sensitive to various influencing factors. The extent of stress arching zone decreases with the increase of an internal friction angle of the joint, lateral pressure coefficient, and overburden depth. In addition, the joint spacing of rock strata is conducive to the development of a stress arch. Results can provide technical support for deformation control and the stability analysis of broken surrounding rock in underground engineering.