The grouting technique is an important method in underground engineering that prevents water seepage and reinforces fractured rock mass. In this research, ultrafine cement-based grouting material, including ultrafine cement (UC), ultrafine fly ash (UFA), polycarboxylate superplasticizer (SP), colloidal nanosilica (CNS), sodium sulfate solution (SS) and water, was developed. The flow time, viscosity, bleeding, setting time and uniaxial compressive strength of the UC-based slurry were measured by orthogonal experiments, and the optimal mix proportion of the UC-based slurry was obtained based on the Taguchi-Grey relational analysis method. Microstructure analysis of the UC-based slurry was conducted using scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) tests. The results showed that the Bingham model could provide a satisfactory description of the rheological properties of the UC-based slurry. The addition of CNS and SS could promote the hydration of the UC-based slurry and improve the microstructure of the hardened slurry, thereby increasing the strength of the hardened slurry. The optimum ratio for the UC-based slurry was water/solid (W/S) ratio of 1.0, and the contents of UFA, SP, CNS and SS by mass of UC were 40%, 0.2%, 4% and 4%, respectively.

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.

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.