Underground tunnels subjected to asymmetric load or ground conditions are susceptible to experiencing uneven longitudinal bending, shearing, and torsional deformations, which further induce cross sectional flattening and warping. The intrinsic damages caused by multiple deformation modes are critical for tunnel health and safety but have long been neglected in practice. In the paper, a three-dimensional analytical model for soil-tunnel interactions was proposed with multiple-mode deformations incorporated, where the tunnel is assumed as a thin-walled pipe resting on an elastic foundation with five deformation modes: bending, shearing, torsion, warping, and flattening. Besides, a three-dimensional variable soil spring model was adopted, accounting for the strata discontinuities in longitudinal and transverse directions. A finite element solution for the proposed model was derived under arbitrary external loads using the principle of minimum potential energy. The validity of the proposed model was substantiated through three case studies. Based on the model, the coupling relationship of tunnel structure in transverse and longitudinal directions was revealed. Furthermore, parametric analysis was conducted to reveal the impact of tunnel width-to-thickness ratio, soil resistance coefficient, and composite strata on tunnel behaviors. These results significantly contribute to a deeper understanding of the intricate behaviors of tunnels, offering potential advancements for improved tunnel design methodologies.

With increasing urbanization, many of the current structures in the underground severely limited the space below ground. Shield tunnels need to be built in curved lines to bypass already established tunnels, pilings, and other buildings. Considering that a curve tunnel is overexcavated on the inner side (overexcavated side) during the excavation process and the difference in the jacking forces on the inside and outside of the tunnel, the study of the curved tunnel working face stability is more complicated. In this paper, a curved tunnel excavation model is designed independently, and the visualized transparent soil model test of the curved tunnel is carried out by combining with particle image velocimetry software to investigate the soil progressive damage process during curved tunnel excavation. On basis of designed modeling tests, a three-dimensional asymmetric spatial pattern of the soil arch was further given by using the numerical simulation method, and a detailed analysis of the internal friction angle and the curvature radius on the arch effect of sandy soil was performed. It is indicated that the soil ahead of the curved tunnel shows the shape of a crescent in the cross section, which is offset toward the inner side, and a bubble shape in the longitudinal section. In addition, the maximum value of the settlement tank during tunneling is located on the inner side of the curved tunnel, and there is an asymmetric distribution of the settlement curve along the central axis. The soil ahead of the curved tunnel's working face will have an increased offset to the inside.

Pile foundations supporting wind turbines and offshore platforms are always subjected to asymmetric lateral cyclic loads from wind and waves. To calculate the lateral response of the pile in sand under asymmetric cyclic loading, this paper proposes a p- y curve model to deal with different levels of load reversal. According to the state of the soil around the pile under asymmetric cyclic loading, the scaling factor of the reloading curve is modified. The soil collapse-recompression model is also extended to apply to different cases of asymmetric cyclic loading according to the characteristics of soil convection during asymmetric cyclic loading. By modifying the shape and position of the p- y curves to different degrees, the lateral response of the pile under asymmetric cyclic loading can be obtained in combination with the improved finite difference method. The validity of the proposed model is demonstrated by comparing the results with the centrifuge model tests. Then, the pile displacement accumulation, the variation of the bending moment, and the soil resistance under asymmetric cyclic loading, are further discussed.

This paper presents a novel strut-free earth retaining wall system for excavation, referred to as the asymmetric double-row pile wall (ARPW) retaining system. This system comprises three key elements: front-row reinforced concrete piles, back-row walls, and connecting crossbeams at the top of the piles. This paper aims to analyze the deformation characteristics and mechanical behavior of the ARPW retaining system, double-row pile wall (DRPW) retaining system, and single-row pile wall (SPW) retaining system using both physical model tests and numerical simulations. The study reveals that, with reasonable row spacing, double-row structures exhibit substantially lower earth pressure and bending moments compared to SPW. Additionally, all double-row structures display reverse bending points. The optimal row spacing for DRPW and ARPW is within the ranges of 2D to 6D and 4D to 8D, respectively. ARPW outperforms DRPW by efficiently utilizing active zone friction force and soil weight force (Gs) to resist overturning moments, thereby resulting in improved anti-overturning capabilities, reduced deformations, lower internal forces, and enhanced stability. The study also presents a case study from the Jinzhonghe Avenue South Side Plot in Tianjin, demonstrating the practical application and effectiveness of the ARPW system in meeting stringent deformation requirements for deep foundation pits. These research findings provide valuable insights for practical engineering applications.

The scouring effect is widely acknowledged as a primary contributor to the weakening in the bearing performance of offshore piles; it often results in asymmetric scour patterns around the pile. To meticulously examine the impact of three-dimensional asymmetric local scour on the lateral bearing performance of a single pile, the Boussinesq solution is employed to determine the effective stress within the soil encompassing the pile, considering the presence of a three-dimensional asymmetric local scour hole. Utilizing the strain wedge model, the calculation method for the lateral bearing performance of a single pile under the condition of three-dimensional asymmetric local scour is established. The validity of this approach is established, and parameter analysis unveils the effect of varying sizes of three-dimensional asymmetric scour holes on the mechanical properties and displacement performance of a single pile. The analysis reveals that, as scouring dimensions around the pile escalate, the impact of scouring on single-pile lateral displacement and internal forces intensifies, leading to a decrease in the lateral bearing performance of a single pile. At a constant scour depth, the bottom area of the upstream scour hole significantly influences the displacement performance of a single pile. When the bottom length Swb1 of the upstream scour hole grows by 1 time, 4 times, and 8 times, the lateral displacement of a single pile at a buried depth of 6 m is augmented by approximately 0.41%, 1.65%, and 2.06%, respectively. The simplified model obtained via the modified strain wedge model and Boussinesq solution can provide a theoretical basis for the preliminary design of a single pile under asymmetric scour hole conditions.