In the underground environment with large buried depth and high ground stress, man-made disturbance is very easy to cause the rapid expansion of primary fractures in the rock, and then developed into the macrodynamic performance of rock. Based on the propagation law of elastic waves in discontinuous media, the application of acoustic emission detection technology can quickly determine whether there are primary fractures in the rock and predict its approximate location. In this work, CT scanning experiments of intact sandstone specimens and fractured sandstone specimens were performed. The gray value distribution of intact sandstone specimens and fractured sandstone specimens was studied. The sandstone specimens were divided into 4 zones (IIV) from top to bottom. The height of each zone is from 0mm to 25mm, and the upper end face of each zone is the starting face. Acoustic emission experiments of intact sandstone and fractured sandstone are carried out based on the equilateral triangle sensor array. The dispersion of AE wave velocity and amplitude in intact sandstone specimens and fractured sandstone specimens is studied. The results show that the crack evolution law of sandstone specimens before and after preloading is closely related to the density distribution. The regular trend is from low density to high density. And the decay law of AE eigenvalue before and after preloading of sandstone specimen is consistent with the change trend of gray value. This shows that it is feasible to explore the spatial location of primary fractures and the degree of development of primary fractures in the rock through the equilateral triangle sensor array. In the actual project, it can provide some guidance and suggestions for related projects.

The increasing problem of urban traffic congestion has led to the extensive use of underground tunnels. However, tunnel lining cracks pose a major threat to the integrity and safety of the structure. Although the traditional repair method is effective, it often requires higher construction technology and higher cost, and may cause damage to the concrete structure. In this study, microbial-induced calcium carbonate precipitation (MICP) was combined with basalt fiber cloth to repair and reinforce tunnel lining cracks. Bacillus pasteurii was used to optimize the microbial mineralization process, and the effectiveness of the method on cracks with different widths was evaluated using a water seepage test. In addition, the mechanical properties of the reinforced tunnel lining were tested. The microbial mineralization process effectively repaired cracks with widths of 1 mm, 2 mm, and 3 mm. The use of unidirectional basalt fiber cloth increased the bearing capacity of the strengthened member by 12.5%. The combined reinforcement method also enhances the deflection performance and alleviates the influence of water seepage on the bonding performance. This innovative and sustainable approach not only provides an effective solution for the repair of tunnel lining cracks, but also contributes to the broader field of eco-friendly building materials. This study highlights the potential of using this combination approach to improve the durability and performance of underground infrastructure.

Primary fractures significantly impacted the stability of surrounding rock in underground projects. Therefore, it is vital to find a solution for the problem of performing a non-destructive detection of rocks and extracting the internal three-dimensional (3D) data field of rocks for visualization analysis. To address this problem, this paper proposed a method of 3D reconstruction for complex cracks in deteriorated sandstone and developed a program based on MATLAB. This work carried out image recognition on the CT scan images of deteriorated sandstone, then implemented a surface reconstruction technique based on object cross-section information, a contour reconstruction technique based on object contour information, a point cloud reconstruction technique for extracting point cloud data of internal cracks in deteriorated sandstone, and a Graphical User Interface (GUI) control system that combines these three reconstruction techniques. The results showed that the 3D reconstruction techniques and the GUI control system proposed in this paper were capable of precisely marking the location of the cracks on a 3D coordinate system and accurately describing their shape with a vector. With only 10 CT scan images, the point cloud reconstruction technique constructed the digital core, and the digital core can quantitatively characterize the influence of primary fractures on the stability of surrounding rock. Additionally, the calculated results of the proposed method were very close to that of Avizo. This method realized the visualization and quantitative characterization of the internal structure of rocks and offered a model for analyzing the stress-fracture-seepage field change during excavation.

The Sichuan Basin in China is one of the most concentrated areas of red beds in China. In the red-bed area, abundant rainfall can easily cause natural disasters, such as landslides, mudslides, collapses, and subsidence. This has had a great impact on the safety of people and property and sustainable modernization in the area. Zhongjiang County of Sichuan Province is a typical red-bed area, and red sandstone is one of the main foundation rocks in this area. Under the influence of rainfall, the strength of red sandstone foundation easily decays, causing disasters such as house collapse. Therefore, in order to explore the influence of rainfall on the mechanical properties of red sandstone, this paper takes the red sandstone in Zhongjiang County, Sichuan Province, China, as the research object and conducts acoustic-emission uniaxial compression experiments under different water contents. The strength characteristics, instability precursor characteristics, fracture types, and damage characteristics of red sandstone in different water-bearing states are obtained. The abovementioned results provide a reference for the Zhongjiang County Government to consider the impact of rainfall on the red sandstone foundation during modernization and emergency management.

There are many hilly areas dominated by red sandstone in western China. At the same time, China is also rapidly advancing the modernization of sustainable development in the abovementioned areas. Therefore, in order to ensure the safety and sustainable advancement of modernization, it has become an urgent task for the local government to explore the mechanical properties of red sandstone in relevant areas. Zhongjiang County, Sichuan Province, China, is mainly dominated by red sandstone, and the study of red sandstone in this area is very rare. Therefore, this paper takes the red sandstone in Zhongjiang County as the research object and studies the damage evolution characteristics of red sandstone under the uniaxial compression load using the acoustic emission monitoring technology. The results show that when the axial stress of red sandstone shows a V-shaped evolution phenomenon and the acoustic emission ringing count enters a relatively quiet period, it indicates that the red sandstone will undergo instability failure. By exploring the evolution law of Ф (AF (ringing count/duration)/RA (rise time/amplitude)), the evolution characteristics of fracture types of red sandstone in the process of damage were found. Based on Weibull function and continuum damage mechanics, the damage evolution model and stress–strain constitutive model are derived. Based on the evolution law of damage variables, the damage evolution characteristics of red sandstone are quantitatively characterized. The research findings provide the government of Zhongjiang County with a reference basis for formulating sustainable construction plans.

China is strengthening the construction of the disaster resistance capacity of its mountain buildings, which increases the demand for RC Diaojiaolou reinforcement technology. In this paper, the performance of RC Diaojiaolou structures (unreinforced and carbon-fiber cloth-reinforced) in an earthquake is studied by a physical model test. The results show that carbon-fiber cloth can effectively improve the seismic capacity. The natural vibration period and acceleration- and displacement-increment coefficients of DF and CDF conformed to the exponential law. The damage process can be divided into three stages: DS, YS, and PS. After reinforcement, the development law of the average value of the acceleration-increment coefficient changed from the N type to the V type, and the development law of the average value of the displacement-increment coefficient changed from the concave type to the V type. The Diaojiaolou was the least affected by the acceleration at I. The displacement deformation of DF was the least affected by the seismic waves at DZ1. The displacement deformation of CDF was the least affected by the seismic waves at I. These findings provide a theoretical basis for the seismic design of mountain Diaojiaolous.