Based on the RNG Κ-ε double-equation turbulence model and the VOF two-phase flow model, the flow regime, flow velocity, pressure, energy dissipation, cavitation and sediment transport characteristics of the double volute chamber vortex shaft were studied using model test and numerical simulation. The results were in good agreement with the experimental values. The vortex chamber was more thoroughly dosed with gas through an aerator device, which reduced the possibility of cavitation erosion. The measured energy dissipation rate exceeded 75%, indicating a good energy dissipation effect. The sediment siltation existed at the bottom of the shaft for various particle sizes at various flow rates, reducing the depth of the stilling well. At low flow operation, the siltation might reached up to 72% of the stilling well’s depth. However, the sediment was cleared away after a big flood and the silt height was lowered to 1.6% of the well depth, enabling the cyclone shaft to have a sufficient water cushion for energy dissipation that would not interfere with its regular functioning. Control the size of the barrage in actual projects to prevent congestion caused by large particles of sediment entering the floodway. In actuality, the operating mode can be altered to control the stilling well’s silting height, ensuring that it has sufficient rich water cushion depth to match the cyclone shaft's design and regular operation requirements.

In order to reveal the influence of the gate opening on the hydraulic characteristics of hydraulic tunnels, a two-dimensional model of silt-releasing tunnel with different gate openings was established. The VOF method and standard κ-ε turbulence model were used for three-dimensional numerical simulation calculation of flow field in abrasive section of flood silt-releasing tunnel. The hydraulic characteristics such as flow state, velocity and pressure near the gate were obtained. The hydraulic characteristics under different gate opening degrees were analyzed to obtain the cavitation number from the gate to the threshold. The results show that when the gate operation opening is less than 1/2 maximum opening, the larger the gate opening is, the smoother the tunnel flow state is, the smoother the flow velocity near the bottom is, the lower the pressure difference between the upstream and downstream of the tunnel floor is. The smaller the gate opening is, the smaller the flow rate in the pressure cave is, and it is easy to cause sediment deposition; The greater the opening of the gate is, the more favorable the overall operation of the tunnel is. The research results have guiding significance for the optimization of the operating opening of the hydraulic tunnel gate and the anti-wear repair of the gate bottom sill.

In order to solve the problem of “seeing the sea in rainy season and having no water to use in drought” in cities in desert areas, taking Kuwait as an example, based on the concept of sponge city in conventional areas, combined with the actual climatic and geological conditions in desert area, the permeability coefficient of 5-50 m underground layer was calculated according to the experimental data obtained from the soil permeability test in N5-1 region. A number of seepage analysis schemes of rainwater storage tank were established, and different schemes were modeled and calculated. The results show that the combination of filling high permeability material around the rainwater storage tank and adding vertical recharge well at the bottom can solve the problem that rainwater cannot penetrate into the underground aquifer effectively.

Ground penetrating radar (GPR) has a broad application prospect in detecting the leakage area of water supply pipeline. In order to enhance the understanding of the response characteristics of GPR in the leakage area and improve the positioning accuracy of the leakage area, based on the finite difference time domain method, this paper simulated the response characteristics of ground penetrating radar for leakage at the bottom of metal pipes, and extracted the "three instantaneous" seismic attribution. The results show that the upper boundary signal of the leakage area is easy to be identified, and the internal signal has multiple reflections and oscillations. The reflection effect of the instantaneous amplitude attribution in the leakage area is similar to that of the original profile. The instantaneous phase attribution is obviously staggered, and the instantaneous frequency attribution is obviously attenuated. Instantaneous phase attribution and instantaneous frequency attribution can reflect the existence of leakage area and weak signal well, so the instantaneous phase attribution and instantaneous frequency attribution are preferred when analyzing the instantaneous attribution of leakage area. The research results can provide a reference for the interpretation of GPR pipeline leakage detection images and practical engineering applications.

In order to further analyze the permeability characteristics of cohesionless soil containing carbonate sand, South China Sea carbonate sand and fine grain quartz powder were used as test materials to prepare test soil samples. The GDS high-pressure triaxial apparatus test system and constant head permeameter were used to carry out research on the influence of carbonate sand content, initial void ratio and effective stress on the permeability characteristics of cohesionless soil. And then an empirical model of permeability coefficient considering effective stress was established. The test results show that when the content of carbonate sand is less than 40%, the grain structure is cohesionless soil matrix, and the pore structure is determined by fine grained soil; The structure of carbonate sand sample is the skeleton structure of sand particles, and the magnitude of permeability coefficient increases significantly; With the increase of effective stress, the permeability coefficient of the sample decreases significantly. An empirical model for the permeability coefficient of cohesionless soil with carbonate sand was established. The model parameters were closely related to the properties of the soil sample. The calculated values were in good agreement with the test values. The research results can provide reference for practical projects.

Aiming at the collapse and failure of high dangerous rock in Zhaojiaya, Xingshan County, numerical simulation methods were used to simulate the stability, evolution law and movement characteristics of the regional dangerous rock mass, so as to obtain the movement track, bounce height and impact energy of the collapsed rock. The results show that the Zhaojiaya dangerous rock has good stability under natural conditions. Under continuous rainfall or rainstorm, the fissure water gradually permeates, and there is the possibility of collapse and failure of the main control structural plane. After the collapse and destruction of the dangerous rock, most of the fallen rock will stay on the slope, and a few of the fallen rock will stop on the road at the foot of the slope after the collision and rebound. Combined with the actual situation of the site and RocFall simulation, the governance measures of "danger clearing + slope leveling + passive protection net" were proposed. The research results can provide reference for similar disaster control projects of high dangerous rock collapse.

The existence of fissures seriously affects the stability performance of rock structures, and how to reasonably describe the characteristic change law of nonlinear mechanics of rocks containing fissures has been an important research point in recent years. Based on this background, a smooth particle dynamics numerical simulation method (RSMPM) is proposed considering material point failure. The RSMPM was based on the basic calculation principle of the MPM algorithm, the Mohr-Coulomb damage criterion was adopted to traverse all material points in each calculation step, and the failure process was carried out for the material points that reach the damage condition. The dynamic fracture process of the rock was described by the failure process of the material points. The accuracy of the proposed numerical simulation method was verified by comparing the numerical simulation results (crack extension process, main stress cloud distribution) of single crack standard cube specimens and single crack Brazilian disc specimens with previous research results. The research results provide a certain reference for the application of smooth particle dynamics methods in rock mechanics engineering and the understanding of rock fracture mechanisms.

In the process of the rise and fall of the reservoir water level in the dry-hot valley reservoir area, the dry and hot conditions in dry and hot valley where the surface rock mass is located need to be considered, that is, the heat and wet cycle. Based on this, repeated shear tests of joint rock sample under heat and wet cycling were carried out. The results show that with the advance of the test period, the shear stress-shear displacement curve decreases as a whole, and the shear strength of the joint surface deteriorates obviously; The deterioration effect of shear strength under repeated shearing is particularly significant only in the initial state after the shear strength is modified; The deterioration effect of shear strength under heat and wet cycle is mainly concentrated in the first five cycles; After modification, the shear strength, cohesion and internal friction angle of the joint surface show a deterioration trend of “first fast and then slow” only under heat and wet cycle, which is consistent with the experimental results. The research results have guiding significance to the deterioration of rock mass and the stability analysis of bank slope in water-level-fluctuation zone of dry-hot valley.

In view of the problem that hydraulic concrete buildings in cold regions are vulnerable to early freezing injury during pouring construction and may affect the later healthy service, in order to study the strength damage law of early frozen concrete and optimize its ratio, Box-Behnken (RSM-BBD) response surface method was used to optimize the experimental design. The RSM response surface model was established by taking water binder ratio, fly ash content and air entraining agent content as variables. A GA-BPNN strength prediction model was constructed to predict the strength of early-frozen concrete accurately. Compared with the RSM model, the results show that the GA-BPNN has more accurate prediction performance and can optimize proportion design more efficiently. The goodness of fit R² and average relative error e_MRE by the GA-BPNN strength prediction model are 0.998 5 and 2.13%, respectively. The relative error between the predicted value of the optimal strength ratio and the experimental value is about 1%. The application of GA-BPNN strength prediction model can realize the efficient optimization of concrete freezing strength and its ratio.

In order to study the mechanical properties and damage mechanism of recycled brick concrete, the shape of recycled aggregate was regarded as a random concave convex polygon. Recycled brick concrete was regarded as seven-phase heterogeneous composite materials such as waste brick aggregate, waste concrete aggregate, new and old mortar, waste brick-new mortar, aggregate-old mortar, new and old mortar. Based on the ABAQUS development program of PYTHON, the numerical model of recycled concrete with different aggregate rate and different brick quantity was established. The meso-mechanical properties of recycled concrete containing brick with 45% coarse aggregate content were analyzed. The damage and failure patterns of recycled concrete containing bricks under load were studied. The results show that the algorithm is efficient in modeling, and can establish the mesoscopic model of recycled concrete containing bricks with different aggregate rates and different brick quantities, which can meet certain engineering requirements; The peak stress and elastic modulus of recycled brick concrete gradually decrease with the increase of brick quantity, while the peak strain increases with the increase of brick quantity; The damage and failure patterns of concrete with different brick quantities are basically the same.