Rock strength is a crucial factor to consider when designing and constructing underground projects.This study utilizes a gene expression programming(GEP)algorithm-based model to predict the true triaxial strength of r...Rock strength is a crucial factor to consider when designing and constructing underground projects.This study utilizes a gene expression programming(GEP)algorithm-based model to predict the true triaxial strength of rocks,taking into account the influence of rock genesis on their mechanical behavior during the model building process.A true triaxial strength criterion based on the GEP model for igneous,metamorphic and magmatic rocks was obtained by training the model using collected data.Compared to the modified Weibols-Cook criterion,the modified Mohr-Coulomb criterion,and the modified Lade criterion,the strength criterion based on the GEP model exhibits superior prediction accuracy performance.The strength criterion based on the GEP model has better performance in R2,RMSE and MAPE for the data set used in this study.Furthermore,the strength criterion based on the GEP model shows greater stability in predicting the true triaxial strength of rocks across different types.Compared to the existing strength criterion based on the genetic programming(GP)model,the proposed criterion based on GEP model achieves more accurate predictions of the variation of true triaxial strength(s1)with intermediate principal stress(s2).Finally,based on the Sobol sensitivity analysis technique,the effects of the parameters of the three obtained strength criteria on the true triaxial strength of the rock are analysed.In general,the proposed strength criterion exhibits superior performance in terms of both accuracy and stability of prediction results.展开更多
The triaxial strength of twenty rockmass types was predicted using two non-linear triaxial strength criteria for rockmass i.e. Modified Mohr-Coulomb(MMC) criterion and Generalized Hoek-Brown(GHB)criterion. Four differ...The triaxial strength of twenty rockmass types was predicted using two non-linear triaxial strength criteria for rockmass i.e. Modified Mohr-Coulomb(MMC) criterion and Generalized Hoek-Brown(GHB)criterion. Four different rockmass classification systems were used for the calculation of MMC criterion parameters while only GSI classification system has been used for calculation of GHB parameters. The representative value of the uniaxial compressive strength and elastic modulus of rockmass have been estimated using probabilistic approach. A hypothetical case of an unsupported tunnel has been analyzed considering both MMC and GHB criteria. The analysis was done using the convergence-confinement method with two different approaches. The first approach predicts the tunnel response using GHB criterion directly. The second approach predicts the tunnel response using equivalent Mohr-Coulomb parameters obtained by linearization of triaxial data points obtained from MMC and GHB criteria. The tunnel response has been estimated in terms of radius of plastic zone, tunnel convergence and tunnel convergence strain. For very poor rockmasses the tunnel response predicted by MMC criterion is less than that predicted by GHB criterion. For poor and fair rockmass, the tunnel response estimated considering both the criteria are comparable except for few cases. Squeezing condition in rockmass has been also evaluated.展开更多
The accurate prediction of the strength of rocks after high-temperature treatment is important for the safety maintenance of rock in deep underground engineering.Five machine learning(ML)techniques were adopted in thi...The accurate prediction of the strength of rocks after high-temperature treatment is important for the safety maintenance of rock in deep underground engineering.Five machine learning(ML)techniques were adopted in this study,i.e.back propagation neural network(BPNN),AdaBoost-based classification and regression tree(AdaBoost-CART),support vector machine(SVM),K-nearest neighbor(KNN),and radial basis function neural network(RBFNN).A total of 351 data points with seven input parameters(i.e.diameter and height of specimen,density,temperature,confining pressure,crack damage stress and elastic modulus)and one output parameter(triaxial compressive strength)were utilized.The root mean square error(RMSE),mean absolute error(MAE)and correlation coefficient(R)were used to evaluate the prediction performance of the five ML models.The results demonstrated that the BPNN shows a better prediction performance than the other models with RMSE,MAE and R values on the testing dataset of 15.4 MPa,11.03 MPa and 0.9921,respectively.The results indicated that the ML techniques are effective for accurately predicting the triaxial compressive strength of rocks after different high-temperature treatments.展开更多
It is of great significance for safety reason to obtain the triaxial compressive properties of cemented tailings backfill(CTB).The influence of cement content,curing age and confining pressure on strength and deformat...It is of great significance for safety reason to obtain the triaxial compressive properties of cemented tailings backfill(CTB).The influence of cement content,curing age and confining pressure on strength and deformation properties of CTB was examined and discussed.Results indicate that the triaxial compressive and deformation behavior of CTB is strongly affected by the cement content,curing age and confining pressure.The increase in cement content,curing age and confining pressure leads to a change in stress−strain behavior and an increase in the axial strain at failure and post-peak strength loss.The cohesion of CTB rises as the curing age and cement content increase.However,the enhancement in internal friction angle is trivial and negligible.It should be noted that the failure pattern of CTB samples in triaxial compression is mainly along a shear plane,the confining pressure restrains the lateral expansion and the bulging failure pattern is dominantly detected in CTB samples as curing age length and cement content increase.The results will help to better understand the triaxial mechanical and deformation behavior of CTB.展开更多
The failure criterion of rocks is a critical factor involved in reliability design and stability analysis of geotechnical engineering.In order to accurately evaluate the triaxial compressive strength of rocks under di...The failure criterion of rocks is a critical factor involved in reliability design and stability analysis of geotechnical engineering.In order to accurately evaluate the triaxial compressive strength of rocks under different confining pressures,a nonlinear empirical strength criterion based on Mohr-Coulomb criterion was proposed in this paper.Through the analysis of triaxial test strength of 11 types of rock materials,the feasibility and validity of proposed criterion was discussed.For a further verification,six typical strength criteria were selected,and the prediction results of each criterion and test results were statistically analyzed.The comparative comparison results show that the prediction results obtained by applying this new criterion to 97 conventional triaxial compression tests of 11 different rock materials are highly consistent with the experimental data.Statistical analysis was executed to assess the application of the new criterion and other classical criteria in predicting the failure behavior of rock.This proposed empirical criterion provides a new reference and method for the determination of triaxial compressive strength of rock materials.展开更多
The strength of lightweight concrete under triaxial compressive stress is studied experimentally with the concrete triaxial apparatus designed by the authors, and is compared with that of normal concrete under the sam...The strength of lightweight concrete under triaxial compressive stress is studied experimentally with the concrete triaxial apparatus designed by the authors, and is compared with that of normal concrete under the same stress state. Ninety-five 100 mm cubes under twenty stress ratios are tested. As compared with normal concrete, it is found that not only the multiaxial compressive strength of lightweight concrete is small, but also the ratio of the multiaxial compressive strength to the uniaxial compressive strength is small. The influence of the intermediate principal stress on the multiaxial strength of lightweight concrete is discussed. The strength criteria which are expressed in the principal stresses and the octahedral stresses respectively are proposed.展开更多
The soil samples were collected from a shallow landslide hazard site of the Rangamati Sadar in Bangladesh to determine the shear strength properties of the soil. Multistage triaxial consolidation undrained test has be...The soil samples were collected from a shallow landslide hazard site of the Rangamati Sadar in Bangladesh to determine the shear strength properties of the soil. Multistage triaxial consolidation undrained test has become worldwide more accepted to determine the shear strength parameters. Multistage triaxial undrained tests were performed on five samples taken from five different depths of boreholes. Samples were evaluated under two natural conditions and three remolded situations. Samples were consolidated before shearing at confining pressures from 50 kPa to 1200 kPa. All the test results are discussed in terms of deviator stress versus axial strain, mean effective stress versus deviator curves, stress ratio versus axial strain, and excess p. w. p. versus axial strain curves. The samples consolidated at low effective stress first displayed peak positive values of excess p. w. p., followed by increased strains due to sample bulging failure, and only a few samples formed a shear surface failure. The strength parameters were estimated using the maximum deviator stress as the failure criterion i.e. the overall value of the cohesion is 20 kPa and the friction angle is 34°. Hence, the critical state line has been constructed and the critical state parameters have been calculated. The critical state stress ratio M was calculated to be 0.036. The shear strength of soil is one of the significant mechanical properties that are thoroughly used to assess the landslide and liquefaction potentiality of the soil.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.42177164)the Distinguished Youth Science Foundation of Hunan Province of China(Grant No.2022JJ10073)the Innovation-Driven Project of Central South University(Grant No.2020CX040).
文摘Rock strength is a crucial factor to consider when designing and constructing underground projects.This study utilizes a gene expression programming(GEP)algorithm-based model to predict the true triaxial strength of rocks,taking into account the influence of rock genesis on their mechanical behavior during the model building process.A true triaxial strength criterion based on the GEP model for igneous,metamorphic and magmatic rocks was obtained by training the model using collected data.Compared to the modified Weibols-Cook criterion,the modified Mohr-Coulomb criterion,and the modified Lade criterion,the strength criterion based on the GEP model exhibits superior prediction accuracy performance.The strength criterion based on the GEP model has better performance in R2,RMSE and MAPE for the data set used in this study.Furthermore,the strength criterion based on the GEP model shows greater stability in predicting the true triaxial strength of rocks across different types.Compared to the existing strength criterion based on the genetic programming(GP)model,the proposed criterion based on GEP model achieves more accurate predictions of the variation of true triaxial strength(s1)with intermediate principal stress(s2).Finally,based on the Sobol sensitivity analysis technique,the effects of the parameters of the three obtained strength criteria on the true triaxial strength of the rock are analysed.In general,the proposed strength criterion exhibits superior performance in terms of both accuracy and stability of prediction results.
文摘The triaxial strength of twenty rockmass types was predicted using two non-linear triaxial strength criteria for rockmass i.e. Modified Mohr-Coulomb(MMC) criterion and Generalized Hoek-Brown(GHB)criterion. Four different rockmass classification systems were used for the calculation of MMC criterion parameters while only GSI classification system has been used for calculation of GHB parameters. The representative value of the uniaxial compressive strength and elastic modulus of rockmass have been estimated using probabilistic approach. A hypothetical case of an unsupported tunnel has been analyzed considering both MMC and GHB criteria. The analysis was done using the convergence-confinement method with two different approaches. The first approach predicts the tunnel response using GHB criterion directly. The second approach predicts the tunnel response using equivalent Mohr-Coulomb parameters obtained by linearization of triaxial data points obtained from MMC and GHB criteria. The tunnel response has been estimated in terms of radius of plastic zone, tunnel convergence and tunnel convergence strain. For very poor rockmasses the tunnel response predicted by MMC criterion is less than that predicted by GHB criterion. For poor and fair rockmass, the tunnel response estimated considering both the criteria are comparable except for few cases. Squeezing condition in rockmass has been also evaluated.
基金We acknowledge the funding support from the National Natural Science Foundation of China(Grant No.51778575)Postdoctoral Science Foundation of China(Grant No.2021M692481)Fundamental Research Funds for the Central Universities of China(Grant No.2042021kf0055).The authors would like to thank the anonymous reviewers and editors for their constructive suggestions which greatly improve the quality of this paper.The authors are also grateful for the permission from Elsevier.
文摘The accurate prediction of the strength of rocks after high-temperature treatment is important for the safety maintenance of rock in deep underground engineering.Five machine learning(ML)techniques were adopted in this study,i.e.back propagation neural network(BPNN),AdaBoost-based classification and regression tree(AdaBoost-CART),support vector machine(SVM),K-nearest neighbor(KNN),and radial basis function neural network(RBFNN).A total of 351 data points with seven input parameters(i.e.diameter and height of specimen,density,temperature,confining pressure,crack damage stress and elastic modulus)and one output parameter(triaxial compressive strength)were utilized.The root mean square error(RMSE),mean absolute error(MAE)and correlation coefficient(R)were used to evaluate the prediction performance of the five ML models.The results demonstrated that the BPNN shows a better prediction performance than the other models with RMSE,MAE and R values on the testing dataset of 15.4 MPa,11.03 MPa and 0.9921,respectively.The results indicated that the ML techniques are effective for accurately predicting the triaxial compressive strength of rocks after different high-temperature treatments.
基金Projects(2018YFC0808403,2018YFE0123000)supported by the National Key Technologies Research&Development Program of ChinaProject(800015Z1185)supported by the Yueqi Young Scholar Project,ChinaProject(2020YJSNY04)supported by the Fundamental Research Funds for the Central Universities,China。
文摘It is of great significance for safety reason to obtain the triaxial compressive properties of cemented tailings backfill(CTB).The influence of cement content,curing age and confining pressure on strength and deformation properties of CTB was examined and discussed.Results indicate that the triaxial compressive and deformation behavior of CTB is strongly affected by the cement content,curing age and confining pressure.The increase in cement content,curing age and confining pressure leads to a change in stress−strain behavior and an increase in the axial strain at failure and post-peak strength loss.The cohesion of CTB rises as the curing age and cement content increase.However,the enhancement in internal friction angle is trivial and negligible.It should be noted that the failure pattern of CTB samples in triaxial compression is mainly along a shear plane,the confining pressure restrains the lateral expansion and the bulging failure pattern is dominantly detected in CTB samples as curing age length and cement content increase.The results will help to better understand the triaxial mechanical and deformation behavior of CTB.
基金Project(51774322)supported by the National Natural Science Foundation of ChinaProject(2018JJ2500)supported by Natural Science Foundation of Hunan Province,China+1 种基金Project(2020JGB135)supported by Degree and Postgraduate Education Reform Project of Central South University,ChinaProject(2018zzts209)supported by the Fundamental Research Funds for the Central Universities,China。
文摘The failure criterion of rocks is a critical factor involved in reliability design and stability analysis of geotechnical engineering.In order to accurately evaluate the triaxial compressive strength of rocks under different confining pressures,a nonlinear empirical strength criterion based on Mohr-Coulomb criterion was proposed in this paper.Through the analysis of triaxial test strength of 11 types of rock materials,the feasibility and validity of proposed criterion was discussed.For a further verification,six typical strength criteria were selected,and the prediction results of each criterion and test results were statistically analyzed.The comparative comparison results show that the prediction results obtained by applying this new criterion to 97 conventional triaxial compression tests of 11 different rock materials are highly consistent with the experimental data.Statistical analysis was executed to assess the application of the new criterion and other classical criteria in predicting the failure behavior of rock.This proposed empirical criterion provides a new reference and method for the determination of triaxial compressive strength of rock materials.
文摘The strength of lightweight concrete under triaxial compressive stress is studied experimentally with the concrete triaxial apparatus designed by the authors, and is compared with that of normal concrete under the same stress state. Ninety-five 100 mm cubes under twenty stress ratios are tested. As compared with normal concrete, it is found that not only the multiaxial compressive strength of lightweight concrete is small, but also the ratio of the multiaxial compressive strength to the uniaxial compressive strength is small. The influence of the intermediate principal stress on the multiaxial strength of lightweight concrete is discussed. The strength criteria which are expressed in the principal stresses and the octahedral stresses respectively are proposed.
文摘The soil samples were collected from a shallow landslide hazard site of the Rangamati Sadar in Bangladesh to determine the shear strength properties of the soil. Multistage triaxial consolidation undrained test has become worldwide more accepted to determine the shear strength parameters. Multistage triaxial undrained tests were performed on five samples taken from five different depths of boreholes. Samples were evaluated under two natural conditions and three remolded situations. Samples were consolidated before shearing at confining pressures from 50 kPa to 1200 kPa. All the test results are discussed in terms of deviator stress versus axial strain, mean effective stress versus deviator curves, stress ratio versus axial strain, and excess p. w. p. versus axial strain curves. The samples consolidated at low effective stress first displayed peak positive values of excess p. w. p., followed by increased strains due to sample bulging failure, and only a few samples formed a shear surface failure. The strength parameters were estimated using the maximum deviator stress as the failure criterion i.e. the overall value of the cohesion is 20 kPa and the friction angle is 34°. Hence, the critical state line has been constructed and the critical state parameters have been calculated. The critical state stress ratio M was calculated to be 0.036. The shear strength of soil is one of the significant mechanical properties that are thoroughly used to assess the landslide and liquefaction potentiality of the soil.
