In the northern area of Jinan City, along the banks of the Yellow River, there was a layer of silty soil approximately 6 to 8 meters below the surface. A large number of landslides were observed in nearby excavations at this depth, demonstrating a different overall failure mode from the conventional circular sliding method for excavations. Based on extensive engineering landslide characteristics, a specific case analysis indicated that the slopes of excavations containing weak interlayers were subjected to a combined circular-plane overall failure mode. This conclusion was validated through numerical analysis using Plaxis finite element software. An analytical solution for the overall stability analysis of excavation slopes with weak interlayers was derived based on statics and moment equilibrium equations. The optimal support scheme was proposed and validated through numerical and monitoring data. The findings suggested that excavation slopes in geological units of the Yellow River alluvial plain in northern Jinan City were influenced by weak interlayers, exhibiting an overall failure mode of circular-plane sliding. The conventional circular sliding calculation method for excavation design posed safety risks. Therefore, the selection of excavation support structures should incorporate shear-resistant elements penetrating the weak interlayers to transform the circular-plane failure mode into circular sliding mode, thus ensuring excavation safety.

The mechanism of surface subsidence induced by shallow buried excavation construction and the failure mode under ultimate state were not unclear. In view of this situation, a scaled model experiment based on particle image velocimetry(PIV)was conducted to simulate the construction process of shallow buried tunnels in sandy soil and Ⅴ-grade surrounding rock. PIV technology was used to analyze the deformation images of the surrounding rock during the construction process of the tunnel, and to obtain displacement cloud maps of geological deformation induced by construction disturbance. By analyzing the characteristics and gradual evolution of surface deformation induced by underground excavation construction disturbance, the shape and range of the failure surface and collapse induced by underground excavation tunnel construction in different strata under the limit state were summarized.The equation of the failure surface induced by the collapse of the arch top strata during underground excavation construction was derived by using the upper limit theorem of limit analysis and variational principle, and the collapse surface graph was drawn.The validity of the model test results was verified by comparing the range of collapse induced by underground excavation construction in the arch crown strata obtained from the model test with the theoretical calculation results.

Drawing from the engineering context of a shallow-buried, biased-load, permeable ribbed double-arch tunnel, the strength reduction method was employed to determine the failure pattern of the surrounding rock at the tunnel's ultimate excavation state. According to the failure characteristics of surrounding rock and the basis of basic assumptions, a fractured sliding surface was hypothesized, and a structural load calculation model for the surrounding rock pressure in the permeable ribbed double-arch tunnel was derived. This model was compared and validated against the results obtained from the stratum structure model. An analysis of the sensitivity of the surrounding rock pressure was conducted. The findings indicated that the tunnel was subjected to asymmetric biased loads, with the vertical load on the side with large buried depth chamber being significantly greater than that on the side with small buried depth chamber. The horizontal load on the right sidewall of the side with large buried depth chamber was significantly greater than the horizontal load on the surface of the left and right lining segments above the central partition wall. The horizontal lateral pressure coefficient was influenced by the slope's biased angle and the internal friction angle of the surrounding rock's sliding surface, with the latter having a more substantial effect. The surrounding rock pressure was closely related to the horizontal lateral pressure coefficient and was influenced by the rock density, the slope's biased angle, and the internal friction angle of the sliding surface. The sensitivity of surrounding rock pressure was significantly impacted by the slope's biased angle and the internal friction angle.

In order to investigate the stress and strain state of the surrounding rock and the effect of supporting structure of the deep buried tunnel through the fault zone in mountainous area, taking Lianfeng Mountain Tunnel Project as the research background, based on ABAQUS large-scale finite element numerical computation program, the mechanics calculation model of the construction of the deep buried tunnel through the fault zone was established, and the change rule of the structural stress state and the horizontal and vertical settlement rule of the mountain after the tunnel excavation and lining were studied. The results showed that the settlement in the fault zone during tunnel excavation was much larger than that in the normal rock body; the stress difference between the surrounding rock and the peripheral mountain body at the fault zone was larger, and the stress difference at the junction with the normal mountain body was larger; the settlement caused by tunnel excavation affected the range of 50 m, and the settlement at the center of the twin tunnels increased with the increase of vertical height; the excavation of the second tunnel in the construction of the twin tunnels caused the increase of the strain of the first tunnel.

In order to study the determination methods of "three major elevations" in the design of underground water sealed caverns, including the elevation of the groundwater level, the elevation of the water curtain system, and the elevation of the oil storage caverns, a method for determining the "three major elevations" from the perspective of water sealing effect on the bases of a certain cavern project was proposed. The water sealing evaluation was also conducted. The analysis results indicated that the regional groundwater drainage datum plane can be taken as the design groundwater level. The design elevations of the water curtain system and the main caverns need to be determined based on a comprehensive consideration of the water sealing effect, the thickness of the "water cover layer" formed above the storage caverns, and the amount of inflow toward the caverns from the surrounding rocks. According to the calculation model established based on the cavern project, the elevation of the designed groundwater level was 25 meters above the water curtain system, and the water curtain system was 25 meters above the storage caverns. The numerical simulation results showed that it has a good water sealing effect, and small adjustments to these elevation parameters can also ensure water sealing. The "three major elevations" are both the key parameters in storage caverns design and the key factors affecting water sealing.

To solve the construction difficulties of the rectangular pipe jacking in the boulder area in a complex geological environment, based on the pipe jacking project of the pedestrian passage of the Qieye Ridge in the transformation project of the Harbor Avenue in Xiangzhou District, Zhuhai City, Guangdong Province, the construction risks encountered by boulders during pipe jacking excavation were analyzed in conjunction with the actual engineering conditions. According to the size, shape, and distribution of the boulders, the advantages and disadvantages of different construction schemes when encountering boulders during pipe jacking construction process were discussed, and the engineering costs, environmental impact, construction difficulty, safety, and applicability of five obstacle handling schemes were systematically compared and analyzed. The best handling method suitable for this case project was selected to achieve the purpose of improving efficiency, reducing costs, and avoiding risks. The case project adopted the pre-treatment construction technology of the down-the-hole hammer in the casing technology to crush and remove the boulders, and successfully restored the pipe jacking excavation construction. This solution could ensure efficient, safe, and orderly clearance work and had excellent application effects.

In order to obtain the failure mechanism of the rock stability under the influence of carbonaceous phyllite band in tailrace surge chamber of Jinchuan Hydropower Station, an insitu microseismic(MS)monitoring system was established. In the construction period, the temporal and spatial distribution of MS events and source parameters were acquired during the excavation in underground caverns. A 3D discrete element numerical model was built. Discrete fracture network(DFN)was added for the weak fault of the underground caverns to build joint fissure, and the displacement and plastic zone distribution were obtained. The synthetic MS events induced by the excavation validated the failure mode and damage of the weak fault. The results suggested that there was a strong correlation between the spatial distribution of insitu MS events and the failure region of rock. The source parameter energy ratio of transverse and longitudinal waves of MS events revealed that the main failure mode of tailrace surge chamber was tension failure. The maximum deformation and plastic zone were obtained by discrete element numerical simulation, and the result was mutually verified with the MS monitoring results. The synthetic MS events generated by DFN-discrete element coupling method revealed the potential failure area of rock, and the result was in good agreement with the actual spatial distribution of MS events.

In order to identify the soil water content in real time, the improved muck with three kinds of fine sand with initial water content were prepared by adding foam with different foam injection ratios, the slag experiment was carried out through the belt slag test platform, the muck images on the belt were obtained, the muck samples were collected accordingly to determine the water content, the water content interval was marked at 1% intervals, and the data set of muck images and water content intervals was established. Through image preprocessing, the texture features of the main image and the edge image of the muck were extracted by using the method of simplified local intensity order pattern combined with completed local binary pattern, and the support vector machine model of particle swarm optimization was selected as the base model, and the integrated learning model for the recognition of water content of the muck was further constructed, which improved the recognition accuracy, and the recognition error of the water content was ±1%.

To explore the dynamic response characteristics of three kinds of assembled tunnel joints(self-weight mortise-tenon joint, bolt mortise-tenon joint and steel plate mortise-tenon joint)under impact load, ABAQUS software was utilized to simulate the dynamic response process and damage characteristics of three kinds of joints under impact load, and the impact resistance of three kinds of joints was compared. The results indicated that the response of the assembled tunnel joint under impact could be divided into initial impact stage, development stage and stable stage. In this process, the joint was affected by impact force, reaction force and inertia force. The dynamic response characteristics of the three types of joints were influenced by the mass and velocity of the impact. When the impact mass exceeds 1 400 kg and the impact velocity exceeds 60 km/h, the central displacement, opening, and damage range of the joints significantly increased. The steel plate tenon and mortise joint was the structure with the best impact resistance among the three types of joints. In the anti-impact design of assembled tunnel structures, it was necessary to focus on enhancing the stiffness of the joints.

The current active control waterproof and drainage system was difficult to achieve dynamic control of water inflows and pressure, which could lead to tunnel cracking and leakage, a pressure valve was installed at the circumferential drainage blind pipe in order to control the water inflow and water pressure. Additionally, the formula for calculating the tunnel water inflow was derived. Using the conformal transformation, the seepage field formula of the surrounding rock was derived from the basic differential equation of the stable seepage field. The tunnel seepage calculation model was further established, incorporating the parameters of circumferential drainage blind pipe spacing and discharge pressure.The calculation formula of tunnel drainage volume and external water pressure of the external water pressure of secondary lining and tunnel water inflow calculation formula was obtained.The decomposition and numerical simulation techniques confirmed the analytical solution's reasonableness.This served as the foundation for the establishment of a tunnel drainage design solution with a pressure valve. The findings indicated that the water pressure and flow rate were significantly impacted by the geotextile permeability coefficient and the spacing between drainage pipes. It was recommended to select a geotextile which permeability coefficient of at least 500 μm/s, and the spacing between drainage blind pipes could be adjusted based on the drainage pressure. The grouting ring thickness could be decreased by adding a pressure valve in comparison to the current active control waterproof and drainage.