The vulnerability zoning of the urban ground subsidence in Tangshan City was investigated in this study, taking into account factors such as the geological lithology, rainfall, population density, road network density, seismic acceleration, and river network density. The main research of this paper is slow land subsidence affecting large territories. A single-factor analysis was conducted using ArcGIS, followed by a grid-weighted overlay analysis. Values were assigned to each factor to generate a vulnerability zoning map. The analytic hierarchy process (AHP) and information value evaluation model were then employed to assess the ground subsidence risk. An evaluation index system was established, comprising the evaluation objective layer, criterion layer, and indicator layer. An evaluation judgment matrix for the ground subsidence risk was constructed, with the calculation of the weight and information value of each risk evaluation indicator, and the total information value of the study area. Four risk levels were determined: high, moderate, relatively low, and low. The findings demonstrate the scientific validity, rationality, and practical applicability of the vulnerability zoning research and risk assessment method for addressing the ground subsidence in Tangshan City. This study contributes to the understanding and management of the ground subsidence risk, providing a robust framework for urban planning and disaster mitigation.

Optimizing the structural cross-sections of power tunnels based on variations in geological strata and burial depths of the power tunnels is essential for their long-term operational safety and maintenance. In this study, the topology optimization theory and finite element methods were applied to derive volume constraints for power tunnels using a straight-wall arch tunnel as an example. Consequently, a topology optimization model for power tunnel structures was established, and the structural characteristics of power tunnels were optimized and analyzed under varying burial depths and elastic moduli using the variable density method. The results indicate that the overall profile of the optimized power tunnel transforms from a straight-wall arch to a multi-centered circle. With the increase in the elastic modulus of the surrounding strata, the internal net height and height-to-span ratio of the tunnel generally show an increasing trend, while the external wall span, vault thickness, invert arch thickness, side wall thickness, and upper arch curvature generally show a decreasing trend. Compared to the elastic modulus of the strata, the burial depth has a relatively smaller impact on the structural profile of the power tunnel. Therefore, when conducting related designs for power tunnels, more emphasis should be placed on understanding the geological conditions of the strata. Subsequently, using the design principles of topology optimization, the power tunnel structure was optimized and a two-dimensional model was developed, incorporating stratigraphic characteristics of the power tunnels. Changes in the bending moment, axial force, safety factor, and other indicators were compared before and after optimization. The results demonstrated that the overall safety performance of the power tunnel lining structure improved notably after optimization, verifying the feasibility of applying topology optimization to power tunnels. These research findings provide valuable reference data for the optimization of power tunnel engineering designs.

To solve the problem of a potential void near a shallow rectangular masonry-concrete power tunnel, the ground-penetrating radar (GPR) detection technology is used and multiple GPR detection lines are placed to detect concealed void. The GPR images of circular and square voids are obtained, which can help increase accuracy of void identification. The models that cover 9 circular voids and 9 square voids are created to investigate how various forms and positions of void will affect the internal forces of the power tunnel structure and surrounding roads. In terms of morphological characteristics, according to the research results, the impact of a circular void on tunnel and surrounding roads is slightly stronger than that of a square void. If the circular void and square void are at 135° and 115°, respectively, the maximum shear force of the tunnel structure occurs at the floor. If both circular and square voids are at 115°, the maximum axial force of tunnel structure occurs at the right side wall. If both circular and square voids are at 135°, the maximum bending moment of tunnel structure occurs at the floor. If both circular and square voids are at 155°, the ground settlement and pavement stress of surrounding roads are maximized. Generally, if a void occurs at the middle or lower part of the side wall or near the side of the floor in a shallow rectangular masonry-concrete power tunnel, its adverse impact is at its worst. Therefore, GPR detection of the voids at the lower and middle parts and the side of the floor in the power tunnel should be intensified, in order to eliminate the risk of a void near power tunnel.