The change of permeability and thickness of deep overburden foundation would affect the seepage field of dam foundation, and then change the erosion evolution process of cutoff wall in dam foundation. In order to study the influence mechanism of multi-structure foundation change on leakage dissolution of cutoff wall, a coupling analysis model of seepage and corrosion of concrete cutoff wall in overburden foundation was proposed by combining fluid mechanics theory, chemical dynamics theory and convection-diffusion equation. The effects of thickness and permeability coefficient of strong permeable layer, weak permeable layer and third permeable layer on calcium ion concentration, porosity and seepage characteristics of cutoff wall were presented. The results show that, with the increase of service years, the calcium ion concentration of the cutoff wall increases rapidly to the peak at first, and then decreases continuously. The porosity and permeability coefficient increase exponentially, and the total seepage flow of the dam increases continuously. Among the influencing factors, the permeability coefficient of weak permeable layer has the greatest influence on the calcium ion concentration, porosity and total seepage flow of the cutoff wall, followed by the thickness and permeability coefficient of strong permeable layer. The service life of concrete cutoff wall under various conditions is from 38.46 a to 44.00 a. The research results can provide theoretical basis for the long-term service performance evaluation of earth-rock dams on multi-structure foundation with deep overburden.

To investigate the effects of different sand rates and aggregate sizes on the fracture toughness of plastic concrete, mechanical property tests and three-point bending notched beam fracture tests were conducted to analyze the physical and mechanical properties and apparent morphology of plastic concrete with different mix ratios. The evolution of fracture toughness of plastic concrete with different sand rates and aggregate sizes was revealed. The results show that the strength and fracture toughness of plastic concrete with different sand rates and aggregate sizes vary significantly. With an increase in the sand content from 45% to 85%, the strength and fracture toughness of plastic concrete exhibit a noticeable decline and an upward trend for aggregate particle sizes in the range of 0 to 5 mm and 5 to 10 mm, respectively, but the variation in fracture toughness is comparatively lower. For aggregate particle sizes ranging from 10 to 20 mm, the specimen strength variation law is comparable to that observed for particle sizes between 5 and 10 mm, with a general upward tendency. With an increase in the sand content from 45% to 85%, the fracture toughness first decreases and then increases. The changes in strength, characteristic load, and fracture toughness of plastic concrete under the same mix ratio conditions are relatively consistent with the variation of aggregate particle size.

Combined with saturated-unsaturated seepage and consolidation theories, a three-dimensional seepage analysis model of a soil slope in the main stream of the Irrawaddy River was established to investigate the change rule of slope stability under different water level reduction magnitude and reduction speed conditions, and to evaluate the reinforcement effect of the micro wood piles on the slope. The results show that the faster the river water level decreases and the higher the water level is during the flood season, the greater the permeation slope drop near the slope surface is during the water level decrease process, and the lower the safety coefficient is. By installing a group of micro wood piles, the slope stability safety coefficient increased by 4.50%, 9.00%, and 39.60%, respectively, when the height of the wood pile group was 2, 4, and 6 m compared with the case of no reinforcement, indicating that the reinforcement effect of micro wood pile group is good and has some popularization value.

Roughness of rock fracture has a significant influence on the seepage characteristics of fracture. The point cloud data of rock fracture surface was collected by three-dimensional (3D) optical scanning system. The joint roughness coefficient (JRC) and surface roughness ratio (R_s) were calculated by SURFER and GEOMAGIC STUDIO, and the quantitative relationship between JRC and R_s was established. The effects of JRC and R_s on the fracture seepage characteristics in limestone were investigated by conducting seepage tests under the coupling effect of stress, seepage and chemical interaction. The results show that JRC is a logarithmic function of R_s, with the R-squared (R²) of 0.9128. The maximum relative error (MRE), mean absolute error (MAE) and root mean square error (RMSE) between the proposed characterization formula and seepage test results are 6.93%, 0.34 and 0.27, respectively. JRC shows quadratic function and logarithmic function with the seepage flow and permeability at stable period, respectively. The fitted relationships of R_s and each parameter are consistent with that of JRC. The larger JRC is, the smaller the seepage flow and permeability are. The values of JRC and R_s of the fracture surface increase under the coupling effect of HMC (hydrological- mechanical-chemical) three fields. The characterization method proposed in this study can be used to estimate the surface roughness of rock fracture. Meanwhile, the value of JRC can be applied to predict the seepage flow and the permeability at stable seepage period.