The fractal model of rock comminution is presented with Mandelbrot's fractal geometry.The results show that it is difficult for those with only a linear similarity ratio to fit practical situations.The comminution...The fractal model of rock comminution is presented with Mandelbrot's fractal geometry.The results show that it is difficult for those with only a linear similarity ratio to fit practical situations.The comminution prob ability of the central part should be considered so the geometric meaning of the constant in Gaudin-Schuhmann's distribution function can be explained more clearly.展开更多
A discontinuous deformation and displacement(DDD) analysis method is proposed for modelling the rock failure process. This method combines the rock failure process analysis(RFPA) method(based on finite element method)...A discontinuous deformation and displacement(DDD) analysis method is proposed for modelling the rock failure process. This method combines the rock failure process analysis(RFPA) method(based on finite element method) and discontinuous deformation analysis(DDA) method. RFPA is used to simulate crack initiation, propagation and coalescence processes of rock during the small deformation state. The DDA method is used to simulate the movement of blocks created by the multiple cracks modelled by the RFPA. The newly developed DDD method is particularly suitable for modelling both crack propagation and block movement during the rock failure process because of the natural and convenient coupling of continuous and discontinuous deformation analyses. The proposed method has been used to simulate crack initiation, propagation and coalescence within a slope as well as the block movement during the landslide process. Numerical modelling results indicate that the proposed DDD method can automatically simulate crack propagation and block movement during the rock failure process without degrading accuracy.展开更多
Thermal cracking is broadly observed in rock engineering.A finite element numerical model which considers the heterogeneity of rock materials and the damage evolution process was used to simulate the thermal cracking ...Thermal cracking is broadly observed in rock engineering.A finite element numerical model which considers the heterogeneity of rock materials and the damage evolution process was used to simulate the thermal cracking behavior of square rock samples heated from the central borehole.The thermal and mechanical behaviors of two cases,i.e.,the case with large size but low heating rate and the case with small size but high heating rate were compared to study the crack initiation location in the models with different model sizes and heating rates.The simulated stress and temperature fields,as well as the failure pattern,were in good agreement with the experimental observations.The temperature and thermal stress distribution during the heating process in both cases indicated that high tensile stress was concentrated around the thermal gradient front,which resulted in the cracks initiating at the location with a certain distance away from the borehole.The results show that under the same heating rate,crack initiation location moves outwards with the increment of the model size then remains approximately at one location,which reflects the boundary-effect.Furthermore,the results indicate that the relative crack initiation locations in two cases are nearly the same if the ratio between the heating rate in two cases(Tx/Ty)nearly equal to the square of the inverse ratio of corresponding model side lengths((ay/ax)2).This concept is named the scale-heating rate equivalence effect in this study.It is beneficial for studying thermal cracking of rock both numerically and experimentally since the model size can be significantly decreased.展开更多
In shale gas fracking, the stimulated natural fracture system is often critical to the gas production. In this paper, we present the results of state-of-the-art modeling of a detailed parametric evolution of the shear...In shale gas fracking, the stimulated natural fracture system is often critical to the gas production. In this paper, we present the results of state-of-the-art modeling of a detailed parametric evolution of the shear stimulation effect in discrete fracture network(DFN) formations. Two-dimensional computational modeling studies have been used in an attempt towards understanding how naturally fractured reservoirs response in hydraulic fracturing. Simulations were conducted as a function of:(1) the in-situ stress ratio;(2) internal friction angle of DFN;(3) DFN orientation with the stress field; and(4) operational vari- ables such as injection rate. A sensitivity study reveals a number of interesting observations resulting from these parameters on the shear stimulation in natural fracture system. This work strongly links the production technology, geomechanical evaluation and aids in the understanding and optimization of hydraulic fracturing simulations in naturally fractured reservoirs.展开更多
基金supported by the National Natural Science Foundation
文摘The fractal model of rock comminution is presented with Mandelbrot's fractal geometry.The results show that it is difficult for those with only a linear similarity ratio to fit practical situations.The comminution prob ability of the central part should be considered so the geometric meaning of the constant in Gaudin-Schuhmann's distribution function can be explained more clearly.
基金supported by the National Basic Research Program of China("973"Project)(Grant No.2014CB047100)the National Natural Science Foundation of China(Grant Nos.51421064,51474046 & 51174039)the Fundamental Research Funds for the Central Universities(Grant No.DUT14LK21)
文摘A discontinuous deformation and displacement(DDD) analysis method is proposed for modelling the rock failure process. This method combines the rock failure process analysis(RFPA) method(based on finite element method) and discontinuous deformation analysis(DDA) method. RFPA is used to simulate crack initiation, propagation and coalescence processes of rock during the small deformation state. The DDA method is used to simulate the movement of blocks created by the multiple cracks modelled by the RFPA. The newly developed DDD method is particularly suitable for modelling both crack propagation and block movement during the rock failure process because of the natural and convenient coupling of continuous and discontinuous deformation analyses. The proposed method has been used to simulate crack initiation, propagation and coalescence within a slope as well as the block movement during the landslide process. Numerical modelling results indicate that the proposed DDD method can automatically simulate crack propagation and block movement during the rock failure process without degrading accuracy.
基金supported by the National Natural Science Foundation of China(Grant No.51874065)the National Major Scientific Instruments Development Project(Grant No.51627804).
文摘Thermal cracking is broadly observed in rock engineering.A finite element numerical model which considers the heterogeneity of rock materials and the damage evolution process was used to simulate the thermal cracking behavior of square rock samples heated from the central borehole.The thermal and mechanical behaviors of two cases,i.e.,the case with large size but low heating rate and the case with small size but high heating rate were compared to study the crack initiation location in the models with different model sizes and heating rates.The simulated stress and temperature fields,as well as the failure pattern,were in good agreement with the experimental observations.The temperature and thermal stress distribution during the heating process in both cases indicated that high tensile stress was concentrated around the thermal gradient front,which resulted in the cracks initiating at the location with a certain distance away from the borehole.The results show that under the same heating rate,crack initiation location moves outwards with the increment of the model size then remains approximately at one location,which reflects the boundary-effect.Furthermore,the results indicate that the relative crack initiation locations in two cases are nearly the same if the ratio between the heating rate in two cases(Tx/Ty)nearly equal to the square of the inverse ratio of corresponding model side lengths((ay/ax)2).This concept is named the scale-heating rate equivalence effect in this study.It is beneficial for studying thermal cracking of rock both numerically and experimentally since the model size can be significantly decreased.
基金supported by the National Natural Science Foundation of China(Grant Nos.4122790141330643&41502294)+2 种基金China Postdoctoral Science Foundation Funded Project(Grant No.2015M571118)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant Nos.XDB10030000XDB10030300&XDB10050400)
文摘In shale gas fracking, the stimulated natural fracture system is often critical to the gas production. In this paper, we present the results of state-of-the-art modeling of a detailed parametric evolution of the shear stimulation effect in discrete fracture network(DFN) formations. Two-dimensional computational modeling studies have been used in an attempt towards understanding how naturally fractured reservoirs response in hydraulic fracturing. Simulations were conducted as a function of:(1) the in-situ stress ratio;(2) internal friction angle of DFN;(3) DFN orientation with the stress field; and(4) operational vari- ables such as injection rate. A sensitivity study reveals a number of interesting observations resulting from these parameters on the shear stimulation in natural fracture system. This work strongly links the production technology, geomechanical evaluation and aids in the understanding and optimization of hydraulic fracturing simulations in naturally fractured reservoirs.
