# A Novel Strutless Double-Row Structure for Deep Excavation: Working Mechanism Study and Analysis
## 1 Introduction
But when excavations are near groundwater, they often require additional measures to prevent groundwater inflow. These measures can significantly extend the project timeline and costs. Traditional support systems such as single-row pile walls (SPWs) face significant challenges in deep excavations, particularly in soft soils where excessive deformations can lead to catastrophic failures. For instance, [PERSON] and [PERSON] [10] documented a case where an SPW system collapsed during the excavation of a metro station in soft clay, causing severe ground settlement and structural damage to adjacent buildings. Similarly, double-row pile wall (DRPW) systems, while offering improved stability, often require complex bracing arrangements that increase construction costs and complexity. The Asymmetric Double-Row Pile Wall (ARPW) system, an evolution of the DRPW, was introduced by [PERSON] and [PERSON] [20]. Characterized by the absence of internal struts and comprising front-row piles, back-row walls (soil-mixed walls), and top crossbeams, the ARPW system has been applied in excavation support projects. The ARPW system addresses these limitations by eliminating the need for internal struts, enhancing anti-overturning capabilities through optimized soil-pile interaction, and providing superior deformation control. By leveraging the stiffness of back-row walls and the active zone friction force, ARPW achieves a balanced stress distribution, making it a viable alternative for projects with stringent deformation requirements. While preliminary applications show improved load-bearing capacity and reduced deformation rates, comprehensive validation of its supporting mechanisms is still lacking. So, this study investigates the performance of ARPW through physical model tests and numerical simulations, offering valuable insights for practical engineering applications. Existing research primarily focuses on the DRPW system, with less attention given to the ARPW system's potential advantages and performance under different conditions. This paper aims to bridge this gap by investigating the deformation and stress characteristics of ARPW, DRPW, and SPW systems. Specifically, we employ a combination of indoor physical model testing and numerical simulations to comprehensively analyze the performance differences among these systems. In the experiments, we designed models with varying row spacings and precisely controlled model scales, boundary conditions, and loading protocols to assess the effects on lateral displacement, pile bending moments, and settlement outside the excavation pit. Additionally, we conducted numerical simulations using Abaqus 2016 to validate our experimental findings. By comparing the performance of these systems, this research provides insights into optimizing ARPW design and construction, thereby advancing understanding and improving design practices in deep foundation pit engineering. Our study not only reveals the significant advantages of the ARPW system in reducing internal forces and enhancing stability but also proposes an optimal range for row spacing (4D to 8D), providing crucial guidance for practical engineering applications. Furthermore, through a case study of the Jinzhonghe Avenue South Side Plot in Tianjin, we verified the effectiveness of the ARPW system in meeting stringent deformation requirements, further demonstrating its superior performance in practical engineering scenarios.