Seepage from the pores of sandstone exposed in deep mines is difficult to block by grouting. In this paper, the permeability evolution of four subcategories of sandstone with different pore structures under different confining pressures, pore water pressures and temperatures is analyzed by experiments. (1) With increasing confining pressure, the permeabilities of the four tested subcategories of sandstone all decrease, but at different rates and to different extents. (2) With increasing pore water pressure, the permeability of subcategory I₁, I₂ and II₁ sandstones increases linearly, while that of subcategory II₂ sandstone decreases following a power function under low confining pressures and tends to be stable under high confining pressures. (3) With increasing temperature, the permeabilities of the four sandstone subcategories decrease at different rates. (4) The orthogonal experimental results show that the confining pressure has the greatest influence on the permeability, followed by the water pressure and temperature. (5) The confining pressure, pore water pressure and temperature produce stress-strain in sandstone and thus change the sandstone pore structure and permeability. The permeability evolution of sandstones varies with pore structure. The findings of this study can inform the classified grouting of deep sandstone and optimize grouting parameters.

In order to verify the applicability of the computer numerical simulation method under complex engineering conditions, and solve the problem that it is difficult to guarantee the normal construction of underground projects with a depth of more than 1 km (it is difficult to carry out multiple field attempts under high-depth conditions, and if you simply use ordinary the calculation method, its calculation accuracy is difficult to guarantee). For the construction of complex geological conditions of an underground mine with a depth of 1300 m in the Central Plains of China, based on the finite difference method (FDM) with high calculation accuracy, using FLAC ^3D software based on FDM, and using progressive design method (PDM), design a variety of different schemes and analyze the mechanism of force and deformation of the surrounding rock mass of the project. Apply the obtained optimal scheme in actual engineering, and monitor the actual force and deformation. Comparing the results of the computer numerical simulation with the monitoring results, the results show that the computer numerical simulation method can also have good application in the actual engineering under the geological conditions of ultra-kilometer depth. It also provides theoretical basis and technical guidance for engineering hypothesis under approximate conditions.

Computer simulation technology is used to solve various engineering problems in the new century, particularly exemplified by the widespread use of numerical simulation research methods. Due to the complicated geological environment, a mine tunnel with a depth of 850 m in Hebei Province has caused various problems, such as large displacements and difficulty in implementing support schemes. However, the complex geological conditions make the project unique, and support schemes for other projects cannot be simply copied. In addition, due to engineering cost requirements, repeatedly evaluating different on-site support schemes is unacceptable. Therefore, it is necessary to obtain an appropriate support scheme through computer simulation technology. Consequently, by implementing FLAC3D software and using the progressive design method (PDM), a variety of support schemes are designed, and simulation tests, such as analysis and optimization of parameters, are performed. The research results show that through the analysis of stress, displacement and other aspects of the various schemes designed by using PDM, the finally selected scheme that was applied to the actual project achieved good results. The findings have proven the feasibility of the method, and the method can guide engineering problems under similar geological conditions.

Ordinary cement is not environmentally friendly, has high cost and lacks superior performance. Many scholars use various admixtures to adjust the properties of cement slurry, but admixtures are usually not environmentally friendly, and it is difficult to ensure that the properties after deployment meet engineering requirements. In this study, a variety of admixtures were obtained using the environmental protection method, and the optimal mixing ratio was analyzed by combining the entropy weight method and the Taguchi grey relational analysis method. The developed cement slurry was compared with conventional slurry from both macroscopic and microscopic aspects. Aiming at the problem that previous scholars lacked the engineering feasibility verification of the developed slurry, this study combined the constitutive equation regression analysis method, discrete element numerical simulation and other methods to study various actual engineering conditions. The results show that the optimal mix ratio of silica fume cement slurry has good permeability characteristics under the conditions of different roughness, grouting pressure and confining pressure. At the same time, under different geological temperatures and different erosive liquid states, the cement slurry stone body shows good properties of reinforcement materials.

Due to the existence of tiny cracks in rock, underground engineering has begun to consider how to divert a large amount of groundwater. To divert groundwater more effectively, it is necessary to master the seepage characteristics of fluids in the micropores of rocks. Based on rock samples obtained from an underground engineering site, this paper analyzes the microscopic pore structure of the rock through a combination of laboratory tests and numerical simulations and inputs this information into a computer model. The fluid seepage state in the rock under different conditions is simulated in the computer model, and parameters such as the fluid seepage velocity in the rock are obtained. Afterwards, it has been verified by engineering practice that the smallest remaining water inflow can reach 0.06‰. The results of this paper can effectively guide the discharge of groundwater to better manage water resources, greatly reduce the pollution of groundwater in construction and production environments, and reduce the pollution caused by grouting projects. Furthermore, the cleanliness and safety of underground engineering construction and production could be ensured.

One type of seepage water that is difficult to plug by grouting is the water exuding through the pores of sandstone in deep underground engineering. Aiming at this problem, this paper collected deep-mine sandstone samples from the Southwest Shandong coalfield, studied the sandstone pore structure and its influential factors by casting thin slices, scanning electron microscopy, mercury intrusion and physical property tests, and selected five representative permeability classification indicators: permeability, porosity, average pore throat radius, comprehensive diagenetic coefficient and sorting coefficient. According to these five indicators, the pore permeability of all the sandstone samples was divided into four subcategories (I₁, I₂, II₁, and II₂) from the perspective of grouting. I₁ has medium pores and medium pore throats that can be filled with ultrafine cement-based slurries; I₂ has medium-small pores and fine pore throats; II₁ has medium-small pores and fine pore throats or small pores and microthroats; both I₂ and II₁ can be filled with chemical slurries; and II₂ has micropores and microthroats that cannot be grouted. This case study provides a reference for the classification and evaluation of the pore permeability of sandstone for grouting and lays a foundation for classified permeation grouting and subsequent pore-expanding permeation grouting.