Theoretical Estimation Of Rock Shear Strength Parameters Based On Normal Distribution Interval Number And Its Application

In the study of the reliability of slope engineering problem how to choose the correct reasonable rock shear strength parameters is essential,at the same time,to explore the value of rock shear strength parameters of the problem is more common in the area of geotechnical engineering the basic research subject.Based on the project of National Natural Science Foundation of China"Study on Joint Distribution of shear strength parameters of rock considering confining pressure Effect",uniaxial test and conventional triaxial test under different confining pressure conditions were carried out after sampling the slope rock mass of open-pit mine and making standard sandstone rock samples.Based on the normal distribution interval number theory and relative p-q method,the interval regression prediction model of sandstone shear strength parameters is established,and the reliability of the open pit slope is analyzed by numerical simulation method,the main content is as follows.Uniaxial compression failure tests and triaxial compression failure tests under different confining pressure conditions were carried out on sandstone samples to obtain uniaxial strength and triaxial compression failure strength of target sandstone samples.Based on the failure characteristics of test samples,the confining pressure effects were analyzed.According to the distribution characteristics of the test data in the chart and its variation with confining pressure,the confining pressure effect and discretization of the triaxial strength of the sample are analyzed in detail.At the same time,descriptive statistics of the experimental data are carried out by using data processing software,which further verifies the previous conclusion that the failure strength of rock under triaxial compression obeies normal distribution under the same confining pressure.By comparing the two commonly used methods for parameter optimization of shear strength:p-q method andσ₁-σ₃ method,a parameter prediction model of shear strength was established based on the principle of p-q method:relative p-q method.Based on the theory of normal distribution interval number and mean confidence interval method,combined with the relative p-q method,a theoretical estimation model of rock shear strength parameters based on the normal distribution interval number was established.The conventional triaxial compression test data were used to verify the estimation model,and it was obtained that the three-way interval number of the normal distribution of the shear strength parameter cohesion c was[20.189,20.670,21.278],and the three-way interval number of the normal distribution of the internal friction coefficient f was[0.581,0.714,0.827].The confidence interval of the shear strength parameter cohesion c is[20.388,20.461],and the confidence interval of the internal friction coefficient f is[0.670,0.748].It is considered that both of them can take into account the uncertainty of the value of shear strength parameters,and the results obtained by the normal distribution of ternary interval number method are more reasonable.Relying on the stope slope of an open-pit sandstone mine in southwest Sichuan,according to the confidence interval model of the mean value,the normal distribution ternary interval number model and the conventional stability analysis method,the slope numerical simulation software is used to establish the numerical model,and the reliability analysis and stability analysis under three working conditions are carried out.The slope safety factors obtained by each method meet the design value of the safety factor under this working condition.The results of reliability analysis show that the value interval of shear strength parameters predicted by the theoretical valuation model based on the number of normal distribution intervals is more reasonable.The research results of this topic can further improve the economy and rationality of slope engineering evaluation method on the basis of the traditional safety factor method.It not only provides a new method for the reasonable value of shear strength parameters in the reliability theory,but also provides a certain theoretical basis for the safety production of open-pit slope.