Study On The Mechanical Behaviors Of Rock Under The Action Of Chemical-Thermal-Hydraulic-Mechanical Effect

Influenced by factors such as temperature,water and chemical corrosion,rock engineering in southwest cold highland area is usually under the effect of multi-field.In order to accurately analyze and evaluate the long-term stability of such rock engineering,a method that can quantitatively characterize and predict the damage of rock under the interaction of chemical-thermal-hydraulic-mechanical effect is urgently needed.In this paper,the mechanism of damage and strength weakening of rock under chemical erosion and freeze-thaw cycle was studied through chemical erosion test and freeze-thaw cycle test.The results show that the essence of the rock damage,whether physical or chemical,is the initiation,propagation,breakthrough and collection of micro-cracks.Therefore,the most direct manifestation of rock damage is the increase of porosity.Thus,the damaged rocks show more obvious plastic deformation and strain softening behavior during the compression process.By using a statistical damage-based approach,a statistical damage constitutive model considering the compaction stage was established.The validity of the statistical damage constitutive model is verified by the test data.The statistical damage constitutive model performs well in each stage of rock compression before failure.For different types of rocks,different confining pressures and different water contents,the statistical damage constitutive model fits well.This model can be applied to most types of rocks and in most engineering environments.Based on the mechanical tests carried out on rock specimens with different porosities and water contents in this study,the combined effects of porosity and water on the mechanical properties and deformation behaviors of rocks were investigated.The test results indicated that the presence of water can significantly reduce the strength and stiffness of rocks and that an increase in porosity enhances the rock-weakening effect of water.While the influence of water on the strength and Young's modulus of rock is significant,the influence of water on the failure strain is negligible.By means of statistical methods,the relationships between the porosity and the mechanical parameters of rocks with different water contents were studied,and empirical equations for the relevant parameters were obtained.Based on the analysis of the results of chemical erosion test and numerical simulation,the amount of dissolution of rock is taken as the index to quantify chemical damage of rock.The formulas for the calculation of the rock strength weakening under the effect of chemical corrosion were established.The damage evolution and strength weakening laws of rock under freeze-thaw cycle were obtained through the statistical analysis of the results of freeze-thaw cycle test.Based on this,formulas for calculating the rock strength weakening under the effect of freeze-thaw coefficient were established.As there is not corresponding function in the current numerical simulation software,it is difficult to realize the numerical simulation of chemical-thermal-hydraulic-mechanical process.According to the researches results of the mechanism of water-rock interactions,chemical damage and freeze-thaw damage of rock,the prediction functions of rock mechanical parameters under the effect of chemical-thermal-hydraulic-mechanical process were established.The numerical simulation of the stability analysis of rock slope under chemical-thermal-hydraulic-mechanical process based on the finite difference method was realized by using the custom functions.The bank slope of steel truss suspension bridge in Jinsha River Canyon in Li JiangShangri-La Railway and the tailings pond of the Tibet Yulong copper mine were selected as engineering examples for the practical application of the functions established in this paper.The results of numerical analysis show that the numerical model established in this paper can effectively simulate the water-rock softening effect,chemical erosion and freeze-thaw damage.The numerical simulation method proposed in this paper can provide a feasible numerical calculation method for most common working conditions in slope engineering,such as rainfall infiltration,rock softening,chemical corrosion and freeze-thaw damage.This will provide relevant experience and theoretical basis for similar projects in the future.