In order to study whether the original design flow can be met after the lining scheme of sections of a long distance non-pressure diversion tunnel is changed, the flow capacity of typical sections of the tunnel was analyzed by model test and theoretical calculation. There are 4 tunnel diameters and 2 roughness in the typical section of the tunnel. In order to meet the conditions of similar resistance, different materials were compared and tested, and the roughness was determined. Through testing and analyzing the flow capacity and flow characteristics at three operating conditions, it is concluded that the flow can be safely passed under operating condition 1, and the clearance margin of some tunnel sections under operating condition 2 is insufficient, with the minimum margin of 14.39%. Most tunnel sections under operating condition 3 do not meet the safety flow. Comparing the test and theoretical calculation, the results of the two are relatively close, and the test value is relatively safe, which can provide a theoretical basis for the construction and operation of the project.

Rock wall crane beam is a common bearing structure in underground powerhouse. Because it is directly supported on the surrounding rock, the stability of the rock crane beam is greatly affected by the geological conditions of the surrounding rock. Taking the rock wall crane beam of phase Ⅱ underground powerhouse of Fengning pumped storage power as an example, the distribution law of rock wall crane beam anchor stress and surrounding rock deformation were explained by analyzing the rock mass structural plane characteristics, the rock mass alteration effect as well as the in-situ observation data of the rock wall crane beam. Furthermore, the correlations between the bolt stress of the crane beam and the deformation of surrounding rock, the geological conditions as well as the construction process were deeply analyzed. The reasons for the large bolt stresses and the large deformations of surrounding rock of the crane beam were then explained, and the influence mechanism of rock mass structural plane and rock mass alteration on the stability of the crane beam was finally revealed. This research can provide technical support for the structural design, the construction organization and the safety demonstration of the rock wall crane beam, thus has practical engineering significance.

In view of the local large deformation, collapse and erosion of silty mudstone entrance section of Daliangshan Highway #2 tunnel, through the field monitoring, indoor swelling test of surrounding rock and 3D modeling analysis, the mechanism of large deformation of initial support was studied. The impact of factors including rainwater, secondary deformation of surrounding rock and silt bias on the large deformation was discussed. The remediation plan was put forward. The results show that the surface clay rock above the tunnel is swelling rock, and the silty mudstone is non-expansive rock, and the tunnel deformation has little affected by the expansion of the surrounding rock. Affected by continuous rainfall, the change in the settlement of the vault is the most obvious, and the settlement increased by 150 mm compared with the pre-rainfall. The theoretical value of horizontal pressure on the deep buried side of the tunnel is 1.73 times that of the shallow side, and the tunnel structure is subjected to obvious bias load. The comprehensive treatment scheme of strengthening temporary support + advanced support of large pipe shed + grouting reinforcement of double-layer small conduit + addition of anti-slip piles at the junction of light and dark at the top of the cave + two rows of pipe piles on the left side of the left hole and two rows of pipe piles in the middle of the left and right holes of the hole section of the hole was adopted, and the deformation of the tunnel was reduced by 87%, and the large deformation of the initial support is effectively controlled.

Based on the instability criterion proposed by the cusp catastrophe theory, the whole surrounding rock was judged, and the relevant tunnel excavation model was established by using the finite element software MIDAS GTS NX, and the changes in surrounding rock stress, displacement and maximum vibration velocity peak in the tunnel-fault system under the conditions of groundwater seepage and blasting were studied by taking No. 2 tunnel project of Daliangshan in Lexi Highway of Sichuan Province for an example. The results show that the comprehensive stiffness ratio of the surrounding rock k<1 and the bifurcation set equation Δ<0 are found by the calculation of the instability criterion, both of which indicate that the surrounding rock has the risk of instability. Under the seepage condition, the maximum principal stress of the fault surrounding rock is 27.71 MPa, and the displacement settlement of the vault is 307.83 mm. Compared with the non-fault area, the stress increases by about 20.64%, and the displacement increases by 105.21%. Influenced by blasting factors, the maximum vertical peak vibration velocity at the fault area is about 13 times that of the common surrounding rock, it is up to 162.97 cm/s. It can be seen that the existence of a fault will have an amplification effect on the dynamic response of surrounding rock. Both theoretical calculation and numerical simulation results show that the F3 fracture of the Daliangshan Tunnel has the risk of instability, and corresponding preventive measures should be taken in advance during construction.

The characteristics and distribution of in-situ stress field have an important influence on the stability and engineering design of the surrounding rock of underground power house. According to the deep surface drilling hole and engineering geological conditions of the underground power house of a pumped storage power station, a three-dimensional numerical analysis model was established, and the inversion reconstruction of the initial in-situ stress field was realized through multiple linear regression analysis. The results show that the maximum horizontal principal stress measured in deep holes is 6.7-17.6 MPa. The magnitude and direction of the inversion model are in good agreement with the measured value, and the horizontal stress in the underground workshop area is dominant, and the maximum horizontal principal stress is 16.2-17.4 MPa. The maximum principal stress azimuth of the stress field in the plant area is less than 30°, and the stress distribution and azimuth angle meet the design requirements. The research results provide a reference for similar large-scale underground projects.

Currently, the researchers have not yet conducted a detailed analysis of the anchor block stability and there exist shortcomings in the discriminatory formula for the slip length. On the basis of the existing computational formulas, the axial force formula for the pipeline was optimized considering expansion joints, and the axial force formula was proposed for downstream elbow pipe without considering the expansion joints. Furthermore, by analyzing axial thrust on pipelines in the context of considering or not considering the expansion joints and comparing the concrete amount of the anchor block under all conditions, the anchor block of the buried steel pipe was found to have the minimum amount of concrete used in the context of not considering the expansion joints and under certain condition, which can provide a reference for future research and design work.

Anti-seepage wall is an important anti-seepage structure in cofferdam, which plays an active role in improving the distribution of seepage field and the stability of cofferdam. This paper presents an optimization method of cutoff wall structure based on artificial fish optimization algorithm. Taking a cofferdam project as an example, the calculation model of cofferdam was established based on finite element analysis, and the wall thickness and rock depth of cutoff wall were taken as the variables to be optimized. Finally, the safety factor of cofferdam under the condition of constant water level and sudden drop of water level was obtained through seepage and stress coupling analysis. Compared with the traditional artificial fish swarm algorithm, the results show that the optimized method based on the improved artificial fish swarm algorithm has faster convergence speed and convergence accuracy, and the optimized anti-seepage wall structure can achieve the balance between the anti-seepage effect and the economy. The pore water pressure behind the cutoff wall decreased significantly, and the safety factors of the cofferdam under the conditions of constant water level and falling water level (falling rates are v=0.5 m/d, 1.0 m/d and 2.0 m/d, respectively) were 1.489, 1.410, 1.376 and 1.321, which met the safety requirements, reflecting the feasibility and rationality of the proposed method. The research results can provide reference for the design and construction of cofferdam.

In response to the inadequacies of traditional earthen and reinforced concrete flood walls that create barriers between urban areas and waterfront regions, which no longer meet the public's demands, the introduction of aluminum alloy flood walls in the Moon Bay flood control renovation project has been proposed. A transformation plan that combines modular flood walls with ecological embankments has been implemented. The post-renovation project has demonstrated excellent operational effectiveness, eliminating the oppressive feel of conventional flood defenses within the urban space. Furthermore, it seamlessly extends the urban landscape space to the water's edge, creating a unified and continuous landscape interface. This approach ensures flood safety while fostering a waterfront landscape with distinctive regional characteristics.

In order to study the impacts of aggregate size and fiber length on the mechanical properties of basalt fiber concrete, three aggregate sizes and basalt fiber lengths have been taken into account, and 108 concrete test blocks (including 72 cubic test blocks and 36 prism test blocks) have been designed and made. Furthermore, axial compression test, splitting tensile test as well as bending test have been carried out to analyze each parameter influence on compression strength, splitting tensile strength and bending strength. On the basis of random fiber script, ABAQUS finite element modeling analysis is carried out, and the corresponding strength calculation has been proposed. The results show that with the increase of aggregate size, the mechanical properties of matrix concrete are improved. While with the adding of basalt fibers, the concrete mechanical properties rise higher than aggregate size increase. The concrete mechanical properties present good performance when 30mm aggregate size mixes with 18 mm and 24 mm basalt fibers. The result of designed random fiber script in ABAQUS finite element modeling matches with the experiment well, and the calculation method considering two-parameter influence of aggregate size and basalt fiber length has good applicability.

Aiming at analyzing the mechanism of slope failure and evolution propagation induced by typhoon and rainstorm, a numerical simulation of the safety state of a slope was carried out based on the measured rainfall data during various typhoons in Fujian Province of China. For the slope before instability, Monte Carlo method was used to calculate the real-time failure probability and reliability index and reveal the transient change characteristics of the seepage field and plastic zone of the slope. For the slope after instability, Herschel-Bulkley-Papanastasiou (HBP) model was used to describe the rheological characteristics of the slope using the SPH method. The propagation process of landslides was analyzed in terms of velocity and accumulation characteristics. The results show that the rainfall is the key factor to induce slope instability. When the slope failure occurs, the sliding speed of the leading edge can reach 15 m/s. This study provides a reference for the early warning and disaster prevention and mitigation of slope engineering under extreme conditions.