In recent years, the development of urban underground space in China, especially the construction and operation of subway tunnels, has greatly relieved the pressure of urban traffic. Due to the imperfect planning of urban facility, many subway tunnels have to be built under the existing utility tunnels (pipe galleries). Nevertheless, shield construction of subway tunnel has a great adverse impact on the deformation and safety of the existing pipe gallery. Therefore, this paper takes Xi’an Metro Line 2 as an example, and studies the safety depth for subway tunnel shield construction under different regional conditions in Xi’an through numerical simulation. The results show that the deformation of the existing pipe gallery and its influence range decrease with the rising buried depth of the double-line subway tunnel when the soil properties are good. For example, in the loess tableland area, when the buried depth of the subway tunnel is greater than 12 m, the settlement deformation of the pipe gallery basically meets the control standard. When the soil properties are poor or the soil properties vary greatly, the subway tunnel excavation has a great impact on the safety of the pipe gallery. For example, in the first-level alluvial fan area with sand layer, when the buried depth of the subway tunnel is less than 24 m and more than 12 m, the deformation standard cannot be satisfied. In addition, in the first-level alluvial fan area with sand layer, the lower soil layer should be treated or the construction parameters should be optimized before the excavation of subway tunnel. The research results can provide reference for similar engineering construction.

During construction of concrete faced rockfill dam (CFRD), the extrusion-sidewall will be protruding or deficiency under normal. Before panel construction, local slope cutting should be taken for the squeezed side wall or supplementary filling measures should be taken after excavating the squeezed side wall, which will affect the mechanical deformation of the panel. According to the monitoring data of concrete-faced rockfill dams of some hydro-electric station in Hubei Province, the three-dimensional finite element analysis method is used to simulate the original filling sequence process of the concrete face rockfill dam. By comparing the difference between the monitoring data and the calculation results, the deformation law of the extrusion side wall and the dam is obtained, which verifies the rationality of the three-dimensional simulation analysis of the dam. The characteristic values of settlement and horizontal displacement obtained from dam monitoring and numerical calculation are compared with those of other high concrete faced rockfill dams. The characteristic values of this dam are close to those of general concrete faced rockfill dams. The deformation law of extrusion side wall and dam under two optimization schemes with different filling sequence is studied. It is found that if conditions permit, the upstream should be filled first and then the downstream to reduce the deformation of extrusion side wall to the upstream.

Layers with low permeability are an important factor affecting the stability of tailings dams. In order to analyze the influence of the weak permeability interlayer on the seepage stability of the dam, this paper establishes a numerical analysis model of the tailings dam with the weak permeability interlayer. The seepage stability of the dam slope is calculated and analyzed for the location, thickness, number, and intervals of mud intercalation on the seepage stability of the dam slope. The weakly permeable interlayers at different locations form different saturation lines in the dam. When the weak permeability interlayer is located in the middle of the dam, the height of the saturation line is the highest, and the corresponding stability safety factor is the smallest. When the weak permeability interlayer moves up or down, the buried depth of the saturation line increases, and the safety factor increases. However, when the weak permeability interlayer is located above the drainage prism, the overall slip along the weak permeability interlayer is incidental to the increase in dam height. When the thickness of the weak permeability interlayer changes, the safety factor of the dam has a positively high significance related to the leakage. When the location of the weak permeability interlayer changes, the safety factor of the dam has no obvious correlation with the leakage. With the increase of the thickness and number of weak pemeability interlayer and the decrease of the intervals of mud intercalation, the height of the saturation line gradually increases, and the safety factor of the dam gradually decreases. Through the location of the sliding surface, it is found that the sliding surface eventually destabilizes through the lowest low-permeability interlayer.

To solve the problem of high-temperature thermal damages to the mine underground driving working face of a dry-hot-rock-enriched area, an active cooling method for fracturing water injection of the surrounding rock of the deep mine is proposed based on analysis of the heat dissipation mechanism of the surrounding rock. An artificial thermal reservoir is formed in the high-temperature rock mass around the tunneling roadway by stimulation, such as a high-pressure crack, and the heat energy of the surrounding rock is extracted by heat exchange of the heat-carrying fluid and the high-temperature rocks mass to reduce the ambient temperature of the roadway. The design of a down hole water injection cooling system based on enhanced geothermal system (EGS) technology is presented and a simplified EGS heats collection model is used for fluid-enclosure. Numerical simulation of the temperature field of the rock coupling shows that the temperature of the surrounding rock can be effectively reduced by increasing the water injection speed and fracture porosity, and improvement of the underground thermal environment can improve the working efficiency. For a water injection rate of 14m/s and porosity of0.18, the average cross section temperature was 41.95?C, which is nearly 5?C lower than the original rock temperature of 46.85?C.