This study compares the strength characteristics of rocks anchored by NPR bolts and ordinary bolts with varied preloads,based on the mechanical properties of NPR bolts(with a negative Poisson’s ratio).The results sho...This study compares the strength characteristics of rocks anchored by NPR bolts and ordinary bolts with varied preloads,based on the mechanical properties of NPR bolts(with a negative Poisson’s ratio).The results show that the uniaxial compressive stress-strain curve of ordinary anchored rocks exhibits noticeable abrupt changes.After reaching peak strength,the bolt breaks,whereas the stress-strain curve of NPR-anchored rocks is smoother.The NPR bolt enters the stage of continuous resistance after reaching maximal strength and does not break.As the preload increases,the strength of the anchored rock grows linearly.A calculation equation for the strength of the anchored rock is proposed based on the preload.The theoretical equation fits the test results well,and the fitted parameters show that NPR bolts can better increase the strength of the rock.The concept of dynamic toughness UC of anchored rock is proposed to reflect the comprehensive mechanical properties of anchored rock,including strength and plasticity.As the preload increases,the UC of ordinary anchored rock first decreases and then increases,while the UC of the NPR anchored rock does not change significantly with the preload when the strain is small,and the UC increases with the increase of the preload when the strain is large.展开更多
To overcome large deformation of deep phosphate rock roadways and pillar damage,a new type of constant-resistance large-deformation negative Poisson’s ratio(NPR)bolt that can withstand a high prestress of at least 13...To overcome large deformation of deep phosphate rock roadways and pillar damage,a new type of constant-resistance large-deformation negative Poisson’s ratio(NPR)bolt that can withstand a high prestress of at least 130 KN was developed.In the conducted tests,the amount of deformation was 200-2000 mm,the breaking force reached 350 KN,and a high constant-resistance pre-stress was maintained during the deformation process.A stress compensation theory of phosphate rock excavation based on NPR bolts is proposed together with a balance system for bolt compensation of the time-space effect and high NPR pre-stress.Traditional split-set rock bolts are unable to maintain the stability of roadway roofs and pillars.To verify the support effect of the proposed bolt,field tests were conducted using both the proposed NPR bolts and split-set rock bolts as support systems on the same mining face.In addition,the stress compensation mechanism of roadway mining was simulated using the particle flow code in three dimensions(PFC^(3D))-fast Lagrangian analysis of continua(FLAC^(3D))particle-flow coupling numerical model.On-site monitoring and numerical simulations showed that the NPR excavation compensation support scheme effectively improves the stress state of the bolts and reduces the deformation of the surrounding rock.Compared to the original support scheme,the final deformation of the surrounding rock was reduced by approximately 70%.These results significantly contribute to domestic and foreign research on phosphate-rock NPR compensation support technology,theoretical systems,and engineering practices,and further promote technological innovation in the phosphate rock mining industry.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
The construction of coal mines often encounters deep composite soft rock roadways,which is characterized by significant deformation and poor stability.To deeply study the failure mechanism and large deformation challe...The construction of coal mines often encounters deep composite soft rock roadways,which is characterized by significant deformation and poor stability.To deeply study the failure mechanism and large deformation challenges of a composite strata roadway in deep and soft rock masses,a numerical model of 3DEC tetrahedral blocks was established based on the method of rock quality designation(RQD).The results showed that original support cannot prevent asymmetric failure and large deformation due to the adverse geological environment and unsuitable support design.According to the failure characteristics,a coupling support of“NPR bolt/cable+mesh+shotcrete+steel pipe”was proposed to control the stability of the surrounding rock.The excellent mechanical properties of large deformation(approximately 400 mm)and high constant resistance force(bolt with 180 k N;cable with 350 k N)were evaluated by the tensile tests.The numerical results showed that the maximum deformation was minimized to 243 mm,and the bearing capacity of the surrounding rock of the roadway was enhanced.The field test results showed that the maximum deformation of the surrounding rock was 210 mm,and the forces of the NPR bolt and cable were stable at approximately 180 k N and 350 k N,respectively.This demonstrated the effectiveness of the coupling support with the NPR bolt and cable,which could be a guiding significance for the safety control of large deformation and failure in deep composite soft rock roadways.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.52174096 and 51874311)。
文摘This study compares the strength characteristics of rocks anchored by NPR bolts and ordinary bolts with varied preloads,based on the mechanical properties of NPR bolts(with a negative Poisson’s ratio).The results show that the uniaxial compressive stress-strain curve of ordinary anchored rocks exhibits noticeable abrupt changes.After reaching peak strength,the bolt breaks,whereas the stress-strain curve of NPR-anchored rocks is smoother.The NPR bolt enters the stage of continuous resistance after reaching maximal strength and does not break.As the preload increases,the strength of the anchored rock grows linearly.A calculation equation for the strength of the anchored rock is proposed based on the preload.The theoretical equation fits the test results well,and the fitted parameters show that NPR bolts can better increase the strength of the rock.The concept of dynamic toughness UC of anchored rock is proposed to reflect the comprehensive mechanical properties of anchored rock,including strength and plasticity.As the preload increases,the UC of ordinary anchored rock first decreases and then increases,while the UC of the NPR anchored rock does not change significantly with the preload when the strain is small,and the UC increases with the increase of the preload when the strain is large.
基金funding support from the National Natural Science Foundation of China(NSFC)(Grant Nos.41941018 and 52304111)the Program of China Scholarship Council(Grant No.202206430007).
文摘To overcome large deformation of deep phosphate rock roadways and pillar damage,a new type of constant-resistance large-deformation negative Poisson’s ratio(NPR)bolt that can withstand a high prestress of at least 130 KN was developed.In the conducted tests,the amount of deformation was 200-2000 mm,the breaking force reached 350 KN,and a high constant-resistance pre-stress was maintained during the deformation process.A stress compensation theory of phosphate rock excavation based on NPR bolts is proposed together with a balance system for bolt compensation of the time-space effect and high NPR pre-stress.Traditional split-set rock bolts are unable to maintain the stability of roadway roofs and pillars.To verify the support effect of the proposed bolt,field tests were conducted using both the proposed NPR bolts and split-set rock bolts as support systems on the same mining face.In addition,the stress compensation mechanism of roadway mining was simulated using the particle flow code in three dimensions(PFC^(3D))-fast Lagrangian analysis of continua(FLAC^(3D))particle-flow coupling numerical model.On-site monitoring and numerical simulations showed that the NPR excavation compensation support scheme effectively improves the stress state of the bolts and reduces the deformation of the surrounding rock.Compared to the original support scheme,the final deformation of the surrounding rock was reduced by approximately 70%.These results significantly contribute to domestic and foreign research on phosphate-rock NPR compensation support technology,theoretical systems,and engineering practices,and further promote technological innovation in the phosphate rock mining industry.
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。
基金supported by the National Natural Science Foundation of China(Grant No.51874311,52174096)。
文摘The construction of coal mines often encounters deep composite soft rock roadways,which is characterized by significant deformation and poor stability.To deeply study the failure mechanism and large deformation challenges of a composite strata roadway in deep and soft rock masses,a numerical model of 3DEC tetrahedral blocks was established based on the method of rock quality designation(RQD).The results showed that original support cannot prevent asymmetric failure and large deformation due to the adverse geological environment and unsuitable support design.According to the failure characteristics,a coupling support of“NPR bolt/cable+mesh+shotcrete+steel pipe”was proposed to control the stability of the surrounding rock.The excellent mechanical properties of large deformation(approximately 400 mm)and high constant resistance force(bolt with 180 k N;cable with 350 k N)were evaluated by the tensile tests.The numerical results showed that the maximum deformation was minimized to 243 mm,and the bearing capacity of the surrounding rock of the roadway was enhanced.The field test results showed that the maximum deformation of the surrounding rock was 210 mm,and the forces of the NPR bolt and cable were stable at approximately 180 k N and 350 k N,respectively.This demonstrated the effectiveness of the coupling support with the NPR bolt and cable,which could be a guiding significance for the safety control of large deformation and failure in deep composite soft rock roadways.
