The shear performance of bolts plays a crucial role in controlling rock mass stability,and the roughness of the joint surface is one of the main factors affecting the mechanical properties of anchored joints.The 2nd g...The shear performance of bolts plays a crucial role in controlling rock mass stability,and the roughness of the joint surface is one of the main factors affecting the mechanical properties of anchored joints.The 2nd generation of negative Poisson ratio(2G-NPR)bolt is a new independently developed material characterized by high strength and toughness.However,the influence of joint surface roughness on its anchorage shear performance remains unexplored.This study involves preparing regular saw-tooth jointed rock masses and conducting laboratory shear comparison tests on unbolted samples,2G-NPR bolts,and Q235 steel anchors.A three-dimensional finite element method,developed by the author,was employed for numerical simulations to analyze the influence of saw-tooth angles on the shear resistance of anchored bolts.The findings show that the anchorage of bolts enhances the shear strength and deformation of saw-tooth rock joints.The 2G-NPR bolts demonstrate superior performance in shear strength and deformation enhancement compared to Q235 steel anchors,including improved toughening and crack-arresting effects.Furthermore,the improvement of the shear strength and displacement of the bolt decreases with the increase of the joint saw-tooth angle.These findings provide a valuable test basis for the engineering application of 2G-NPR bolts in rock mass stabilization.展开更多
Active faults are a common adverse geological phenomenon that can occur during tunnel excavation and has a very negative impact on the construction and operation of the tunnel.In this paper,the grade IV rock surroundi...Active faults are a common adverse geological phenomenon that can occur during tunnel excavation and has a very negative impact on the construction and operation of the tunnel.In this paper,the grade IV rock surrounding the cross-fault tunnel with poor geological conditions has been chosen for the study.The support capacity of 2^(nd) Generation-Negative Poisson’s Ratio(2G-NPR)bolt in an active fault tunnel has been carried out on the basis of relevant results obtained from the geomechanical model test and numerical investigations of failure model for existing unsupported fault tunnel.The investigation shows that surrounding rock of the tunnel is prone to shear deformation and crack formation along the fault,as a result,the rock mass on the upper part of the fault slips as a whole.Furthermore,small-scale deformation and loss of blocks are observed around the tunnel;however,the 2G-NPR bolt support is found to be helpful in keeping the overall tunnel intact without any damage and instability.Due to the blocking effect of fault,the stress of the surrounding rock on the upper and lower parts of the fault is significantly different,and the stress at the left shoulder of the tunnel is greater than that at the right shoulder.The asymmetrical arrangement of 2G-NPR bolts can effectively control the asymmetric deformation and instability of the surrounding rock.The present numerical scheme is in good agreement with the model test results,and can reasonably reflect the stress and displacement characteristics of the surrounding rock of the tunnel.In comparison to unsupported and ordinary PR(Poisson’s Ratio)bolt support,2G-NPR bolt can effectively limit the fault slip and control the stability of the surrounding rock of the fault tunnel.The research findings may serve as a guideline for the use of 2G-NPR bolts in fault tunnel support engineering.展开更多
2G-NPR bolt (the 2nd generation Negative Poisson’s Ratio bolt) is a new type of bolt with high strength, high toughness and no yield platform. It has signifcant efects on improving the shear strength of jointed rock ...2G-NPR bolt (the 2nd generation Negative Poisson’s Ratio bolt) is a new type of bolt with high strength, high toughness and no yield platform. It has signifcant efects on improving the shear strength of jointed rock mass and controlling the stability of surrounding rock. To achieve an accurate simulation of bolted joint shear tests, we have studied a numerical simulation method that takes into account the 2G-NPR bolt's tensile–shear fracture criterion. Firstly, the indoor experimental study on the tensile–shear mechanical properties of 2G-NPR bolt is carried out to explore its mechanical properties under diferent tensile–shear angles, and the fracture criterion of 2G-NPR bolt considering the tensile–shear angle is established. Then, a three-dimensional numerical simulation method considering the tensile–shear mechanical constitutive and fracture criterion of 2G-NPR bolt, the elastoplastic mechanical behavior of surrounding rock and the damage and deterioration of grouting body is proposed. The feasibility and accuracy of the method are verifed by comparing with the indoor shear test results of 2G-NPR bolt anchorage joints. Finally, based on the numerical simulation results, the deformation and stress of the bolt, the distribution of the plastic zone of the rock mass, the stress distribution and the damage of the grouting body are analyzed in detail. The research results can provide a good reference value for the practical engineering application and shear mechanical performance analysis of 2G-NPR bolt.展开更多
第二代负泊松比(second-generation negative Poisson’s ratio bolts,2G-NPR)锚杆逐渐应用于裂隙岩体加固,为研究2G-NPR锚杆在充填结构面中的抗剪性能,采用室内直剪试验对比分析了不同充填厚度下2G-NPR锚杆和普通钢筋(Q235)锚杆锚固结...第二代负泊松比(second-generation negative Poisson’s ratio bolts,2G-NPR)锚杆逐渐应用于裂隙岩体加固,为研究2G-NPR锚杆在充填结构面中的抗剪性能,采用室内直剪试验对比分析了不同充填厚度下2G-NPR锚杆和普通钢筋(Q235)锚杆锚固结构面的剪切力学行为。结果表明,相同充填厚度下,2G-NPR锚杆较Q235锚杆弹性阶段剪切刚度低,峰值抗剪强度高、峰值剪切位移大;随着充填厚度增加,虽然两类锚杆的峰值抗剪强度变化相差不大,但由于2G-NPR锚杆的高吸能、高延展特性,其峰值剪切位移优势明显,使得试样延性得到一定提升。锚杆轴力监测数据表明,2G-NPR锚杆能够有效补偿其与灌浆体解耦造成的轴力突降,且持荷能力更持久;其平均峰值轴力为Q235锚杆的3.17倍,且随着充填厚度增加,峰值轴力持续上升,锚固性能更为稳定。进一步结合声发射监测发现,相同充填厚度下,2G-NPR锚杆的最大累计计数和最大累计能量更低,b值(声发射小事件数与大事件数的比值)下降时间更晚,试样破坏程度更小,揭示2G-NPR锚杆提升试样延性的原因在于其有效吸收了剪切应变能,减缓了裂纹的扩展。研究结果可为2G-NPR锚杆在软硬互层岩体支护工程中的应用提供指导。展开更多
基金Project(GZB202405561)supported by the Postdoctoral Fellowship Program of China Postdoctoral Science FoundationProject(42377154)supported by the National Natural Science Foundation of China。
文摘The shear performance of bolts plays a crucial role in controlling rock mass stability,and the roughness of the joint surface is one of the main factors affecting the mechanical properties of anchored joints.The 2nd generation of negative Poisson ratio(2G-NPR)bolt is a new independently developed material characterized by high strength and toughness.However,the influence of joint surface roughness on its anchorage shear performance remains unexplored.This study involves preparing regular saw-tooth jointed rock masses and conducting laboratory shear comparison tests on unbolted samples,2G-NPR bolts,and Q235 steel anchors.A three-dimensional finite element method,developed by the author,was employed for numerical simulations to analyze the influence of saw-tooth angles on the shear resistance of anchored bolts.The findings show that the anchorage of bolts enhances the shear strength and deformation of saw-tooth rock joints.The 2G-NPR bolts demonstrate superior performance in shear strength and deformation enhancement compared to Q235 steel anchors,including improved toughening and crack-arresting effects.Furthermore,the improvement of the shear strength and displacement of the bolt decreases with the increase of the joint saw-tooth angle.These findings provide a valuable test basis for the engineering application of 2G-NPR bolts in rock mass stabilization.
基金supported by the National Natural Science Foundation of China(NSFC)(41941018)the Program of China Scholarship Council(202106430031)。
文摘Active faults are a common adverse geological phenomenon that can occur during tunnel excavation and has a very negative impact on the construction and operation of the tunnel.In this paper,the grade IV rock surrounding the cross-fault tunnel with poor geological conditions has been chosen for the study.The support capacity of 2^(nd) Generation-Negative Poisson’s Ratio(2G-NPR)bolt in an active fault tunnel has been carried out on the basis of relevant results obtained from the geomechanical model test and numerical investigations of failure model for existing unsupported fault tunnel.The investigation shows that surrounding rock of the tunnel is prone to shear deformation and crack formation along the fault,as a result,the rock mass on the upper part of the fault slips as a whole.Furthermore,small-scale deformation and loss of blocks are observed around the tunnel;however,the 2G-NPR bolt support is found to be helpful in keeping the overall tunnel intact without any damage and instability.Due to the blocking effect of fault,the stress of the surrounding rock on the upper and lower parts of the fault is significantly different,and the stress at the left shoulder of the tunnel is greater than that at the right shoulder.The asymmetrical arrangement of 2G-NPR bolts can effectively control the asymmetric deformation and instability of the surrounding rock.The present numerical scheme is in good agreement with the model test results,and can reasonably reflect the stress and displacement characteristics of the surrounding rock of the tunnel.In comparison to unsupported and ordinary PR(Poisson’s Ratio)bolt support,2G-NPR bolt can effectively limit the fault slip and control the stability of the surrounding rock of the fault tunnel.The research findings may serve as a guideline for the use of 2G-NPR bolts in fault tunnel support engineering.
基金supported by the National Natural Science Foundation of China(NSFC)(41941018).
文摘2G-NPR bolt (the 2nd generation Negative Poisson’s Ratio bolt) is a new type of bolt with high strength, high toughness and no yield platform. It has signifcant efects on improving the shear strength of jointed rock mass and controlling the stability of surrounding rock. To achieve an accurate simulation of bolted joint shear tests, we have studied a numerical simulation method that takes into account the 2G-NPR bolt's tensile–shear fracture criterion. Firstly, the indoor experimental study on the tensile–shear mechanical properties of 2G-NPR bolt is carried out to explore its mechanical properties under diferent tensile–shear angles, and the fracture criterion of 2G-NPR bolt considering the tensile–shear angle is established. Then, a three-dimensional numerical simulation method considering the tensile–shear mechanical constitutive and fracture criterion of 2G-NPR bolt, the elastoplastic mechanical behavior of surrounding rock and the damage and deterioration of grouting body is proposed. The feasibility and accuracy of the method are verifed by comparing with the indoor shear test results of 2G-NPR bolt anchorage joints. Finally, based on the numerical simulation results, the deformation and stress of the bolt, the distribution of the plastic zone of the rock mass, the stress distribution and the damage of the grouting body are analyzed in detail. The research results can provide a good reference value for the practical engineering application and shear mechanical performance analysis of 2G-NPR bolt.
文摘第二代负泊松比(second-generation negative Poisson’s ratio bolts,2G-NPR)锚杆逐渐应用于裂隙岩体加固,为研究2G-NPR锚杆在充填结构面中的抗剪性能,采用室内直剪试验对比分析了不同充填厚度下2G-NPR锚杆和普通钢筋(Q235)锚杆锚固结构面的剪切力学行为。结果表明,相同充填厚度下,2G-NPR锚杆较Q235锚杆弹性阶段剪切刚度低,峰值抗剪强度高、峰值剪切位移大;随着充填厚度增加,虽然两类锚杆的峰值抗剪强度变化相差不大,但由于2G-NPR锚杆的高吸能、高延展特性,其峰值剪切位移优势明显,使得试样延性得到一定提升。锚杆轴力监测数据表明,2G-NPR锚杆能够有效补偿其与灌浆体解耦造成的轴力突降,且持荷能力更持久;其平均峰值轴力为Q235锚杆的3.17倍,且随着充填厚度增加,峰值轴力持续上升,锚固性能更为稳定。进一步结合声发射监测发现,相同充填厚度下,2G-NPR锚杆的最大累计计数和最大累计能量更低,b值(声发射小事件数与大事件数的比值)下降时间更晚,试样破坏程度更小,揭示2G-NPR锚杆提升试样延性的原因在于其有效吸收了剪切应变能,减缓了裂纹的扩展。研究结果可为2G-NPR锚杆在软硬互层岩体支护工程中的应用提供指导。
