The decline in groundwater level is a key factor contributing to cover collapse in karst areas. In this study, the model tests and numerical simulations are conducted to reveal the breeding process and formation mechanism of cover collapse sinkholes caused by the decline of groundwater level in karst area. Firstly, the model tests confirm that the decline of groundwater level generates negative pressure at the lower edge of overlying soil. The negative pressure experiences four distinct phases during the groundwater drawdown process: rapid rise, slow decline, rapid decline, and gradual dissipation. The maximum negative pressure is influenced by the particle size distribution of the overlying soil. Then, the numerical simulations are carried out to investigate the change process of negative pressure caused by the loss of fillers in karst pipe. The simulated results indicate that the rate of groundwater decline and the thickness and initial void ratio of the overlying soil can affect the maximum negative pressure. As groundwater level drops, a negative pressure zone forms underground, causing tensile failure in the surrounding soil and creating an arched soil hole, which weakens the support for the overlying soil. This phenomenon can also lead to the collapse of the overlying soil under its self-weight. Groundwater table decline in karst areas can result in both internal and surface collapses. When the overlying soil is thin, internal and surface collapses occur simultaneously. In contrast, for thick overlying soil, internal collapse happens first, followed by a layer-by-layer collapse, ultimately forming sinkholes. Finally, the breeding process and formation mechanism of the Yujiawan Reservoir sinkholes are discussed. Geological conditions and groundwater level decline significantly affect internal collapse in karst areas, requiring careful consideration from on-site engineers.

The water environment greatly affects the creep deformation of recycled aggregate concrete (RAC). Hence, a humidity–stress–damage coupling numerical model was used for investigating the time-dependent deformation of RAC in the water environment in this study. Firstly, uniaxial compression and water absorption tests were performed to determine the calculation parameters of the creep numerical simulation of RAC in a water environment. Experimental results indicate that the elastic modulus and compressive strength drop as the water content increases. Then, the time-dependent deformation of RAC in a water environment was studied using a numerical simulation test of compressive creep when multiple stress levels were applied, and the critical stress for accelerated creep and the long-term strength of RAC were obtained. Finally, the influence of confining pressures on the long-term deformation of RAC in a water environment was discussed. When there is no confining pressure, the long-term strength of RAC is 23.53 MPa. However, when a confining pressure of 3.921 MPa is loaded onto RAC, the long-term strength of RAC is 47.052 MPa, which increases by 100%. Increasing confining pressures has an obvious effect on ensuring the long-term stable application of RAC in a water environment. Compared with the creep test, the method adopted in this study saves time and money and provides the theoretical basis for evaluating the time-dependent deformation of RAC in a water environment.