Jianwei Zhang

Cemented sand and gravel (CSG) dams have been widely applied due to their simple construction and use of local materials. With the increasing occurrence of extreme weather events, temperature has become an important factor affecting the safe operation of dams. To investigate the temperature stress response of CSG dams under low-temperature conditions and achieve cross-scale analysis, an adaptive macro–meso finite element method is proposed. Through an iterative “solution–evaluation–mesh adjustment” procedure, meso-scale modeling is performed in high-stress regions, and the results are compared with those obtained using the conventional submodeling method. The results show that, under low-temperature conditions, temperature gradients and thermal stresses are mainly concentrated near the dam surface, with limited influence on the interior, while hydraulic load remains the dominant controlling factor. The local stress distribution patterns obtained by the two methods are generally consistent, and both can reflect stress concentration near the aggregate–mortar interfaces. The proposed method can characterize local meso-scale responses within a global computational framework, providing a reference for cross-scale analysis of the temperature response and the identification of local unfavorable stress regions in CSG dams.

To explore the stress-bearing characteristics of the “inner tensioned steel ring–segment–surrounding rock” composite structure in TBM (Tunnel Boring Machine) pressurized water conveyance tunnels, a 3D refined finite element model for this composite structure was established, with the Class V surrounding rock section of the TBM pressurized water conveyance tunnel in the Rongjiang-Guanbu water diversion project selected as the research subject. The effects of the internal water pressure, surrounding rock type and tunnel burial depth on the mechanical properties of the composite structures are studied. The findings demonstrate that reinforcing the tunnel structure with an inner tensile steel ring can effectively constrain tunnel deformation, diminish the tensile stress of segments and the extent of tensile zones, and enhance the bearing capacity of the composite structure. Under the effect of internal water pressure, the compressive stress of segments, vertical deformation, joint opening degree, stress of connecting bolts, stress of the inner tension ring, and stress of anchor rods all exhibit a reduction compared to the scenario without internal water pressure. Under the combined action of external water–soil pressure and internal water pressure, variations in surrounding rock types lead to respective increases of 37.16%, 15.75%, and 15.12% in the stress of connecting bolts, segment joint misalignment, and anchor bolt stress. As the tunnel burial depth increases, the stress of connecting bolts and the vertical deformation of segment and the joint misalignment of the pipe segment increase by 140%, 107% and 60.61%, respectively. In addition, under the combined action of external water and soil pressure and internal water pressure, the load-sharing ratios of the surrounding rock, pipe segment, inner tension ring and anchor rod are 34.87%, 34.59%, 21.59% and 8.95%, respectively, and the load-sharing ratio of the inner tensioned ring is 85.80% higher than that observed in the absence of internal water pressure, indicating that internal water pressure effectively enhances the load-sharing performance of the inner tensioned steel ring. In the composite structure, the load-sharing ratio of surrounding rock decreases as the surrounding rock class increases (from Class III to Class V). Under the same load condition, the load-sharing ratio of Class III surrounding rock is 7.14% higher than that of Class V. As the tunnel burial depth increases, the inner tensioned steel ring and anchor rods function more prominently as reserve-bearing components. When the tunnel burial depth reaches 71 m, the load-sharing ratio of the inner tension steel ring and anchor rod increases by 19.91% and 55.72%, respectively, compared with that of the buried depth of 31 m. The research results can provide a theoretical reference for the lining design and late reinforcement measures of similar tunnel projects.

To investigate the dynamic response patterns of basalt-fiber-reinforced concrete slabs under random wave loads, this study characterized wave characteristics based on the random wave theory. Numerical simulations of wave loads were conducted using the Morrison equation, and an analytical model for basalt-fiber-reinforced concrete slabs was established. The research systematically examined the influence mechanisms of two key factors—effective wave period and incident angle—on the dynamic properties of such components. The results indicate that when the effective wave period increases from 7 s to 11 s, the peak displacement, peak stress, peak strain, and stress in the basalt-fiber reinforcement of the slab decrease by 12.79 mm, 0.93 MPa, 130 με, and 229.25 MPa, respectively. The growth rate of the component’s dynamic response first increases and then decreases as the effective wave period shortens. When the wave incidence angle increased from 18° to 90°, the peak displacement, peak stress, peak strain, and stress in the basalt-fiber reinforcement of the concrete slab increased by 17.87 mm, 1.32 MPa, 155 με, and 297.97 MPa, respectively. The growth rate of the component’s dynamic response exhibited a continuous increase with the increasing wave incidence angle. At an incidence angle of 18°, the values of the aforementioned four indicators were 576%, 213%, 52.5%, and 46% higher than those under the 90° condition, respectively. The findings of this study provide theoretical support and data references for elucidating the dynamic response patterns of basalt-fiber-reinforced concrete-slab structures under varying wave-loading conditions and for conducting fatigue performance research.

Owing to the insufficient understanding of the mechanical properties and damage mechanisms of concrete-rock bonding interfaces in dam foundations, this study establishes a refined three-dimensional simulation model for direct shear tests of concrete-rock bonding interfaces based on in-situ direct shear tests conducted at a reservoir. The damage evolution process and failure mechanisms of the concrete-rock interface under different loading conditions are investigated. The results indicate that under varying normal stresses, the shear stress-shear displacement curve exhibits an initial increase followed by a gradual decrease, with peak shear strength ranging from 1.074 MPa to 2.073 MPa and a maximum error of 8.48%, meeting engineering requirements. The damage evolution process of the concrete-rock interface under different normal forces was simulated and compared with in-situ direct shear test results, confirming the accuracy of the simulation. The failure modes of the concrete-rock interface under different loading conditions can be categorized into three types: bonding interface failure, mixed shear failure, and rock failure. The failure mode is closely related to the magnitude of normal stress—as normal stress increases, the area of shear fracture along the bonding interface expands, and the fracture surface becomes smoother. The findings provide a theoretical basis for the design, anti-sliding stability, and risk analysis of similar concrete gravity dams.

It is significant to adopt scientific temperature control criteria for high concrete dams in the construction period according to practical experience and theoretical calculation. This work synthetically uses information entropy and a cloud model and develops novel in situ observation data-based temperature control indexes from the view of a spatial field. The order degree and the disorder degree of observation values are defined according to the probability principle. Information entropy and weight parameters are combined to describe the distribution characteristics of the temperature field. Weight parameters are optimized via projection pursuit analysis (PPA), and then temperature field entropy (TFE) is constructed. Based on the above work, multi-level temperature control indexes are set up via a cloud model. Finally, a case study is conducted to verify the performance of the proposed method. According to the calculation results, the change law of TFEs agrees with actual situations, indicating that the established TFE is reasonable, the application conditions of the cloud model are wider than those of the typical small probability method, and the determined temperature control indexes improve the safety management level of high concrete dams. Research results offer scientific reference and technical support for temperature control standards adopted at other similar projects.

The dam-break water flow is a complex fluid motion, showing strong nonlinearity and stochasticity. In order to better study the characteristics of the dam burst flood, the smooth particle hydrodynamics (SPH) method was chosen to establish a two-dimensional classical dam-burst model, and the flow velocity distribution graph was obtained by calculation and compared with the experimental results in the literature, and the fitting degree of the two was obtained to be 88.4%, which verifies the validity of the model. On this basis, according to the principle of dam failure, the two failure modes of equal-interval gradual failure and progressive gradual failure were simulated, and the water body characteristics such as water flow velocity, energy, pressure, etc., were analyzed based on the different working conditions of the two modes to obtain the characteristics of gradual dam-failure water flow under the two kinds of numerical models. The simulation results show that, compared with the instantaneous dam failure mode, (1) the flow rate of the dam-failure stream reaching the downstream slows down in the gradual dam-failure mode; (2) the depth development of the breach extends downward in layers and stages over time, and the overall duration of the breach is prolonged; (3) the destructive power of the dam-failure flood is weakened as the number of segments increases. The results of the study show that, compared with the instant dam-failure mode, the calculation results of the breach development considering the progressive gradual dam-failure mode are more in line with the theoretical solution and closer to the actual process of dam failure, which can provide ideas and references for advancing the numerical study of dam failure.

In this paper, the fluid–solid interaction problem involving structural movement and deformation is considered, and an SPH (smoothed particle hydrodynamics) interaction method is proposed to establish a numerical fluid–solid model and to correct the particle velocities in the momentum conservation equations. It is found that, when the smoothing coefficient is equal to 0.93, the similarity of the free surface curves reaches up to 91.9%, and calculations are more accurate. Under the same working conditions, the classical model of elastic sluice discharge is established based on the SPH method and the finite element method, and the validity and accuracy of the model based on the SPH method are verified by analyzing the flow pattern of the sluice discharge, the opening of the elastic gate, and the change trend in the free liquid surface curve. On this basis, a number of characteristic points on the sluice gate are selected based on the SPH model to investigate the change rule of pressure at the fluid–solid interface, and the results are as follows: (1) based on the numerical model established by the SPH method, the flow pattern of the water, the opening of the elastic gate, and the change in the free liquid level curve are all in better agreement with the experimental results in the literature than those of the finite element method, and the computational results are also better; (2) the pressure of the solid on the fluid at each characteristic point is equal to the pressure of the fluid on the solid, which satisfies the principle of action–reaction and laterally verifies the nature of the dynamic boundary between the fluid and the solid, further verifying the validity of the program; and (3) in the process of sluice discharge, the elastic sluice presents a large force at both ends and a small force in the middle, meaning that the related research in this paper can act as a reference for flow–solid interaction problems related to sluice discharge.