Deformation modulus of rock mass is one of the input parameters to most rock engineering designs and constructions.The field tests for determination of deformation modulus are cumbersome,expensive and time-consuming.T...Deformation modulus of rock mass is one of the input parameters to most rock engineering designs and constructions.The field tests for determination of deformation modulus are cumbersome,expensive and time-consuming.This has prompted the development of various regression equations to estimate deformation modulus from results of rock mass classifications,with rock mass rating(RMR)being one of the frequently used classifications.The regression equations are of different types ranging from linear to nonlinear functions like power and exponential.Bayesian method has recently been developed to incorporate regression equations into a Bayesian framework to provide better estimates of geotechnical properties.The question of whether Bayesian method improves the estimation of geotechnical properties in all circumstances remains open.Therefore,a comparative study was conducted to assess the performances of regression and Bayesian methods when they are used to characterize deformation modulus from the same set of RMR data obtained from two project sites.The study also investigated the performance of different types of regression equations in estimation of the deformation modulus.Statistics,probability distributions and prediction indicators were used to assess the performances of regression and Bayesian methods and different types of regression equations.It was found that power and exponential types of regression equations provide a better estimate than linear regression equations.In addition,it was discovered that the ability of the Bayesian method to provide better estimates of deformation modulus than regression method depends on the quality and quantity of input data as well as the type of the regression equation.展开更多
Based on the Global Navigation Satellite System(GNSS)velocity in North China from 1999 to 2018,the deformation parameters,such as the strain rate,the velocity profiles,and the fault slip rates,are analyzed.The princip...Based on the Global Navigation Satellite System(GNSS)velocity in North China from 1999 to 2018,the deformation parameters,such as the strain rate,the velocity profiles,and the fault slip rates,are analyzed.The principal conclusions are as follows:1)the GNSS results during 1999-2007 can effectively reflect the deformation characteristics of North China,and the strain rate shows SEE tensile feature in the Shanxi seismic zone with a maximum value of 0.7×10^(-8)/yr.Meanwhile,the deformation is characterized by left-lateral features in the Yinshan seismic zone and Zhangjiakou-Bohai seismic zone with a maximum shear strain rate of 0.7×10^(-8)/yr.2)In the period of 1999-2007,the GNSS velocity profiles show that the deformation is mainly distributed in a range of 100-km width crossing the Yinshan seismic zone and the middle section of the Zhangjiakou-Bohai seismic zone,and 50-km width crossing the Zhangjiakou-Bohai seismic zone near the Bohai Bay.3)The deformation response to the 2011 Japan MW9.0 earthquake shows a significant difference between the middle and east sections of the Zhangjiakou-Bohai seismic zone,and the deformation loading rate decreased from 3.3 mm/yr in 1999-2007 to 2.6 mm/yr and 0.9 mm/yr in the 2013-2018 period for above two sections respectively.Furthermore,the fault slip rates inverted from GNSS measurements show a similar dynamic adjustment process,reflecting the weak impact of the Japan MW9.0 earthquake on the deformation around the central section of the Zhangjiakou-Bohai seismic zone.4)From the results of GNSS strain rate,velocity profile and fault slip rate,we suggest that the potential of the strong earthquake should be high in the Yinshan seismic zone and the middle section of the Zhangjiakou-Bohai fault zone.展开更多
The directional dependency of the acoustic emission （AE） and deformation rate analysis （DRA） methods was analyzed, based on the contact bond model in the two-dimensional particle flow code （PFC2D） in two types o...The directional dependency of the acoustic emission （AE） and deformation rate analysis （DRA） methods was analyzed, based on the contact bond model in the two-dimensional particle flow code （PFC2D） in two types of rocks, the coarse-grained sandstone and Aue granite. Each type of rocks had two shapes, the Brazilian disk and a square shape. The mechanical behaviors of the numerical model had already been verified to be in agreement with those of the physical specimens in previous research. Three loading protocols with different loading cycles in two orthogonal directions were specially designed in the numerical tests. The results show that no memory effect is observed in the second loading in the orthogonal direction. However, both the cumulative crack number of the second loading and the differential strain value at the inflection point are influenced by the first loading in the orthogonal direction.展开更多
Non-destructive techniques of in-situ stress measurement from oriented cored rocks have great potential to be developed as a cost cost-effective and reliable alternative to the conventional overcoring and hydraulic fr...Non-destructive techniques of in-situ stress measurement from oriented cored rocks have great potential to be developed as a cost cost-effective and reliable alternative to the conventional overcoring and hydraulic fracturing methods.The tangent modulus method(TMM)is one such technique that can be applied to oriented cored rocks to measure in-situ stresses.Like the deformation rate analysis(DRA),the rock specimen is subjected to two cycles of uniaxial compression and the stress-tangent modulus curve for the two cycles is obtained from the stress-strain curve.A bending point in the tangent modulus curve of the first cycle is observed,separating it from the tangent modulus curve of the second cycle.The point of separation between the two curves is assumed to be the previously applied maximum stress.A number of experiments were conducted on coal and coal measured rocks(sandstone and limestone)to understand the effect of loading conditions and the time delay.The specimens were preloaded,and cyclic compressions were applied under three different modes of loading,four different strain rates,and time delays of up to one week.The bending point in the stress-tangent modulus curves occurred approximately at the applied pre-stress levels under all three loading modes,and no effect of loading rate was observed on the bending points in TMM.However,a clear effect of time delay was observed on the TMM,contradicting the DRA results.This could be due to the sensitivity of TMM and the range of its applicability,all of which need further investigation for the in-situ stress measurement.展开更多
文摘Deformation modulus of rock mass is one of the input parameters to most rock engineering designs and constructions.The field tests for determination of deformation modulus are cumbersome,expensive and time-consuming.This has prompted the development of various regression equations to estimate deformation modulus from results of rock mass classifications,with rock mass rating(RMR)being one of the frequently used classifications.The regression equations are of different types ranging from linear to nonlinear functions like power and exponential.Bayesian method has recently been developed to incorporate regression equations into a Bayesian framework to provide better estimates of geotechnical properties.The question of whether Bayesian method improves the estimation of geotechnical properties in all circumstances remains open.Therefore,a comparative study was conducted to assess the performances of regression and Bayesian methods when they are used to characterize deformation modulus from the same set of RMR data obtained from two project sites.The study also investigated the performance of different types of regression equations in estimation of the deformation modulus.Statistics,probability distributions and prediction indicators were used to assess the performances of regression and Bayesian methods and different types of regression equations.It was found that power and exponential types of regression equations provide a better estimate than linear regression equations.In addition,it was discovered that the ability of the Bayesian method to provide better estimates of deformation modulus than regression method depends on the quality and quantity of input data as well as the type of the regression equation.
基金financially supported by the National Science Foundation of China(41974011)funded by the National Key R&D Program of China[2018YFC1503606]。
文摘Based on the Global Navigation Satellite System(GNSS)velocity in North China from 1999 to 2018,the deformation parameters,such as the strain rate,the velocity profiles,and the fault slip rates,are analyzed.The principal conclusions are as follows:1)the GNSS results during 1999-2007 can effectively reflect the deformation characteristics of North China,and the strain rate shows SEE tensile feature in the Shanxi seismic zone with a maximum value of 0.7×10^(-8)/yr.Meanwhile,the deformation is characterized by left-lateral features in the Yinshan seismic zone and Zhangjiakou-Bohai seismic zone with a maximum shear strain rate of 0.7×10^(-8)/yr.2)In the period of 1999-2007,the GNSS velocity profiles show that the deformation is mainly distributed in a range of 100-km width crossing the Yinshan seismic zone and the middle section of the Zhangjiakou-Bohai seismic zone,and 50-km width crossing the Zhangjiakou-Bohai seismic zone near the Bohai Bay.3)The deformation response to the 2011 Japan MW9.0 earthquake shows a significant difference between the middle and east sections of the Zhangjiakou-Bohai seismic zone,and the deformation loading rate decreased from 3.3 mm/yr in 1999-2007 to 2.6 mm/yr and 0.9 mm/yr in the 2013-2018 period for above two sections respectively.Furthermore,the fault slip rates inverted from GNSS measurements show a similar dynamic adjustment process,reflecting the weak impact of the Japan MW9.0 earthquake on the deformation around the central section of the Zhangjiakou-Bohai seismic zone.4)From the results of GNSS strain rate,velocity profile and fault slip rate,we suggest that the potential of the strong earthquake should be high in the Yinshan seismic zone and the middle section of the Zhangjiakou-Bohai fault zone.
基金supported by the National Natural Science Foundation of China (Grant No. 50978083)the Fundamental Research Funds for the Central Universities (Grants No. 2009B07714 and 2010B13914) in Chinathe Innovation Project for Graduate Students of Jiangsu Province (Grant No. CX10B_215Z)
文摘The directional dependency of the acoustic emission （AE） and deformation rate analysis （DRA） methods was analyzed, based on the contact bond model in the two-dimensional particle flow code （PFC2D） in two types of rocks, the coarse-grained sandstone and Aue granite. Each type of rocks had two shapes, the Brazilian disk and a square shape. The mechanical behaviors of the numerical model had already been verified to be in agreement with those of the physical specimens in previous research. Three loading protocols with different loading cycles in two orthogonal directions were specially designed in the numerical tests. The results show that no memory effect is observed in the second loading in the orthogonal direction. However, both the cumulative crack number of the second loading and the differential strain value at the inflection point are influenced by the first loading in the orthogonal direction.
基金financially supported by the Australian Coal Association Research Program(ACARP)under project C29010.
文摘Non-destructive techniques of in-situ stress measurement from oriented cored rocks have great potential to be developed as a cost cost-effective and reliable alternative to the conventional overcoring and hydraulic fracturing methods.The tangent modulus method(TMM)is one such technique that can be applied to oriented cored rocks to measure in-situ stresses.Like the deformation rate analysis(DRA),the rock specimen is subjected to two cycles of uniaxial compression and the stress-tangent modulus curve for the two cycles is obtained from the stress-strain curve.A bending point in the tangent modulus curve of the first cycle is observed,separating it from the tangent modulus curve of the second cycle.The point of separation between the two curves is assumed to be the previously applied maximum stress.A number of experiments were conducted on coal and coal measured rocks(sandstone and limestone)to understand the effect of loading conditions and the time delay.The specimens were preloaded,and cyclic compressions were applied under three different modes of loading,four different strain rates,and time delays of up to one week.The bending point in the stress-tangent modulus curves occurred approximately at the applied pre-stress levels under all three loading modes,and no effect of loading rate was observed on the bending points in TMM.However,a clear effect of time delay was observed on the TMM,contradicting the DRA results.This could be due to the sensitivity of TMM and the range of its applicability,all of which need further investigation for the in-situ stress measurement.
