Serious environmental pollution exacerbates the extent of water-rock interaction. The physical and mechanical properties as well as microstructure of engineering rock mass are changed due to the water-rock interaction, having a significant effect on the long-term stability of rock engineering. Creep characteristic of rock plays an important role in analyzing and evaluating the long-term stability of rock mass engineering. In order to investigate the creep mechanical behavior and hydrochemical corrosion mechanism of red sandstone under water-rock interaction, the red sandstone from Taoyuan hydropower station in Hunan province was taken as the research object, and then a series of triaxial compression creep tests were performed on the red sandstone after immersing into salt solutions with different ion concentrations and pH values. The results show that: The water-rock chemical corrosion damage of red sandstone is closely correlated to the ion concentration and pH value of salt solution. The stronger the acid-base property and the higher the ion concentration are, the greater the secondary porosity and the bigger the volumetric expansion deformation is. Meanwhile, the creep deformation and instantaneous deformation increase. Nevertheless, the long-term strength shows a decreasing tendency when the ion concentration increases or the pH value decreases. The sensitivity of red sandstone to chemical solution is as follows: acidic salt solution＞alkaline salt solution＞neutral salt solution＞distill water. The curves of axial steady-state creep strain rate versus deviatoric stress all exhibit a “S”-shaped characteristic. The relationship of axial steady-state creep strain rate with deviatoric pressure can be well described by an exponential function. Based on the experimental results, the hydrochemical corrosion mechanism on creep behavior of red sandstone is preliminarily discussed.

In order to study the unloading mechanical properties of rock under different seepage pressures, this paper selects the sandstone as the research object, conducts triaxial unloading tests under different seepage pressures and different stress paths, and compares the results with conventional triaxial tests. The rock strength characteristics under different stress paths are compared, and the effect of seepage pressure on the rock deformation and strength parameters is further analyzed. The test results show that the increase of seepage pressure will weaken the rock strength, the peak strength of rock decreases with the increase of seepage pressure, and the axial deformation increases with the increase of seepage pressure. Aiming at two different unloading stress paths, under the condition of constant axial pressure and unloading confining pressure, the cohesion of rock keeps decreasing and the internal friction angle increases; under the condition of increasing axial pressure and unloading confining pressure, the cohesion of rock keeps increasing and the internal friction angle decreases.

Stepwise landslide warning surface model is presented based on moving least squares. Based on the monitoring data of the Wangjiapo landslide in Three Gorges Reservoir area, the proposed model is set up, and its ability to provide early warning of the stepwise deformation is validated. The cumulative displacement-monitoring period curve is fitted via moving least squares, and its derivative is used to determine the range of the stepwise deformation during the landslide. The maximum point of its second derivative within the deformation range is taken as the “quasi-failure point” to obtain the current rainfall, previous rainfall, and displacement rate thresholds of each stepwise deformation. The threshold surface of the stepwise deformation is constructed with the monitoring information of the “quasi-failure point” by using moving least squares. A four-level warning threshold surface model is established with the displacement rate as the classification standard for early warning analysis. The validation results of the Wangjiapo landslide show that the warning level is consistent with the actual displacement of the landslide. The model has good early warning effect and enables warning of landslide stepwise deformation.

In order to study the influence of confining pressure and pore pressure on the mechanical properties and deformation parameters during underground tunnel excavation, a gas-undrained triaxial compression test of layered phyllite was carried out with argon as the permeable medium. The study analyzed the evolution characteristics of stress-strain relationship, peak strength, deformation characteristics and failure modes of layered phyllite with bedding inclinations under varying confining pressure and pore pressure. Additionally, an anisotropy degree formula based on bedding inclinations was introduced to discuss the impacts of confining pressure and pore pressure on the anisotropy of layered phyllite. The results show that the peak strength of layered phyllite increases gradually as the pore pressure decreases or the confining pressure increases. The peak strength σ_c, elastic modulus and deformation modulus exhibit ‘U’ shaped changes with an increase in bedding inclinations. When the bedding inclination ranges between 30° and 60°, the layered phyllite has a low degree of hardness, and the predominant failure mode is shear slip along the bedding plane. Furthermore, the layered phyllite is greatly affected by confining pressure and pore pressure in the direction of parallel bedding, showing significant anisotropic characteristics.