Study On Pore Water Pressure Increment-Strength Reduction Limit Analysis Method And Its Engineering Application

The slope engineering has the characteristics of significant difference in rock and soil properties,complex environment,large volume,great harm and difficult repair,and permeability and pore water pressure have a significant impact on slope stability.Now,the fluid-solid coupling limit analysis mainly adjusts the position of the infiltration surface and applies the corresponding hydrostatic pressure through empirical methods,resulting in a certain difference between the analysis results and the actual situation.In this paper,the pore pressure increment-shear strength reduction limit analysis method(PISSR)was proposed by revealing the relationship between pore(void),composition structure and shear strength of saturated rock and soil,and constructing the shear strength functionelle of rock and soil.Furthermore,PISSR,shear strength reduction method(SSR)and Bishop method were used to analyze the influencing factors of elastoplastic fluid-solid coupling under 18working conditions and the stability analysis of two typical sections of large open-pit slope.And the field displacement monitoring,investigation and inspection were done.PISSR was applicability.The main works and conclusions are as follows:(1)Based on the structural characteristics of rock and soil materials,the relationship between shear strength parameters and pore water pressure,and the principle of effective stress,the shear strength functionelle of rock and soil is established.The strength reduction method of effective stress shear strength and PISSR are proposed.(2)Based on the effective stress principle of volume compression deformation of saturated rock and soil materials,the method of determining the pore(void)water pressure increment and the approximate calculation method of rock pore water pressure increment.(3)Used PISSR and SSR to analyze the stability of saturated soft rock slope,the research shows that Raising infiltration surface and increasing permeability coefficient,the slope safety reserve factor of PISSR and the slope safety reserve factor of SSR decrease 6%～13%and 3%～6%respectively.When permeability coefficient is same,the infiltration surface position of PISSR rises by 4.8%～14%.The safety reserve factors be influenced by the unit time infiltration(infiltration rate)above the soaking surface,and there is the critical number.When the infiltration amount is 0.01m~3/s,the safety reserve factors calculated of PISSR are about 3%～8.5%lower than that calculated by SSR.After the infiltration amount reaches 0.05m~3/s,the safety reserve factors calculated by the two methods are consistent.(4)Fluid-solid coupling limit analysis of engineering slope stability of two typical sections shows that the safety reserve factors,the slope sliding surface position,shear opening position and seepage point position analyzed by PISSR are in good agreement with the actual situation on site,which means that the pore pressure increment-strength reduction method has certain applicability in the stability of saturated rock slope.There are 55 figures,23 tables and 71 references in this paper...