Research And Application Of Drucker-Prager Intensity Criterion Based On Energy Mechanism

The rock mass involved in tunnel,rock slope,water conservancy and hydropower projects are usually geological bodies with defects such as joints,cracks and weak structural planes.In order to ensure the stability of rock mass engineering,it is of engineering significance to establish a criterion for predicting rock mass strength.Among the commonly used strength criteria,the D-P strength criterion is simple in expression,and the yield trajectory in the plane is a circle,but the calculation accuracy and applicability are not high.Based on the D-P strength criterion,the generalized D-P rock mass strength criterion is established by introducing the evaluation index of rock mass quality from the perspective of energy.The main conclusions are as follows:(1)Establishment of generalized D-P rock mass criterion.In order to extend the D-P strength criterion to rock mass,the value formula of rock mass parameters is established by introducing geological strength factor GSI,integrity coefficient KV,disturbance coefficient D and stratified inclination Angle θ,and the generalized D-P rock mass strength criterion is established based on elastic strain energy.(2)Theoretical analysis of generalized D-P rock mass criterion.The generalized D-P rock mass criterion introduces the evaluation index of rock mass,and the yield surface radius of the plane becomes smaller,which can effectively reflect the essence of rock mass failure under low stress state.When the material is complete rock,GSI=100、KV=1、D=0,without considering the stratified inclination,the rock mass parameters are equal to the rock parameters,and the generalized D-P rock mass criterion deforms to the generalized D-P criterion.Generalized D-P rock mass criterion is a set of strength criteria based on rock mass deformation parameters.The yield failure trajectory in π plane is a cluster of concentric circles.Generalized D-P rock mass criterion is the inheritance and development of generalized D-P rock mass criterion.(3)Data validation of generalized D-P rock mass criterion.According to the field triaxial test data of columnar jointed basalt,bedded shale and fractured rock,the peak strength of rock mass is calculated by D-P criterion,generalized D-P rock mass criterion and generalized three-dimensional H-B criterion respectively.The calculated errors of the generalized D-P rock mass criterion and the experimental data are respectively columnar jointed basalt(4.7%),bedded shale(16.3%)and fractured small rock mass(11.6%),while the generalized three-dimensional H-B criterion calculation errors are columnar jointed basalt(7.6%)and bedded shale(23.2%).The results show that the calculation accuracy of generalized D-P rock mass criterion meets the error requirement,and generalized D-P rock mass strength criterion is successfully extended to rock mass.(4)The embedding of generalized D-P rock mass constitutive model.Based on the D-P constitutive model built in the finite element software,the generalized D-P constitutive model is embedded into the finite element software and verified by a simple tunnel excavation model.The results show that the stress and displacement of tunnel surrounding rock are large based on the generalized D-P rock mass criterion,and there are two reasons.On the one hand,the generalized D-P rock mass criterion introduces rock mass deformation parameters and considers the rock mass quality evaluation indexes(GSI and KV),so the displacement of tunnel surrounding rock is too large.On the other hand,the cohesive force of the rock mass fitted in this paper is large,which is assigned to the generalized D-P rock mass constitutive model,resulting in greater stress of the tunnel surrounding rock.(5)Generalized D-P rock mass criterion reliability analysis.The limit state equation of generalized D-P rock mass criterion is established based on the first order distance method,and the influence of mean value and variance(variation coefficient)of rock mass deformation parameter on the reliability of generalized D-P rock mass criterion is analyzed with rock mass deformation parameter as a single variable.The results show that the reliability of rock mass calculated by generalized D-P rock mass criterion is relatively higher when the mean value of rock mass deformation parameters increases and the rock mass is more broken.The variation coefficient of rock mass deformation parameters has little influence on the reliability probability of generalized D-P rock mass criterion.