摘要
采用全长锚固锚杆对巷道支护时,高应力软岩的连续变形引起锚杆内力分布产生复杂变化。为探究全长锚固锚杆承载特征,特别是杆体由正常承载到临界及脱黏承载时的力学特性演化规律,以巷道开挖面空间效应下的围岩二次释放位移为基础,考虑围岩塑性阶段的强度软化和体积扩容特征,建立锚杆-围岩在正常支护、临界支护和滑移脱黏3种典型工况下的相互作用模型,推导出锚杆轴力与锚固界面剪应力沿杆长分布的解析解,并系统地分析滞后支护距离(支护时机)、扩容系数、锚杆长度、残余剪切强度、托盘反力等对杆体内力分布规律的影响。研究结果表明:(1)在正常支护工况下,锚杆内力分布符合中性点理论。锚杆轴力由孔口沿杆体快速上升,在中性点处达到峰值后向着孔底呈现指数衰减特征,锚固界面剪应力在孔口至中性点部分由最大值快速衰减至0,之后沿杆体先增大后减小,中性点两侧的剪应力方向相反。锚杆轴力和锚固界面剪应力均随着滞后支护距离的增加而减小,随着扩容系数、锚杆长度的增加而增大。(2)在支护临界工况下,锚杆中性点移动至孔口,轴力在孔口处达到最大,并沿杆体向孔底方向快速衰减为0;锚固界面剪应力呈“拱形”分布,杆体两端剪应力为0,方向指向孔底,对围岩产生明显的压应力作用。在较软弱围岩条件下,较早支护时机和较大锚杆长度均有利于快速提高锚杆锚固力,但杆体易在孔口附近发生破断。(3)在滑移脱黏工况下,锚杆孔口处的脱黏范围与扩容系数、锚杆长度呈正相关,与残余剪切强度呈负相关。随着滑移脱黏范围增加,中性点向孔底侧偏移,锚固界面剪应力分布演化为“双峰”曲线,轴力集中程度显著降低,对围岩的有效压应力作用减小;锚固界面滑移脱黏导致杆体的载荷传递能力极大减弱,锚杆锚固能力难以有效发挥,通过施加托盘可使锚固界面上产生开裂的应力及时转移至托盘上,从而有效抑制滑移脱黏现象。
When full-length anchoring bolts were used to support roadways,the deformations of high-stress soft rocks caused complex changes in the internal force distribution of bolts.The work explored the bearing characteristics of full-length anchoring bolts,especially the evolution law of the mechanical properties of bolt bodies from normal bearing to critical and debonding bearing.The strength-softening and volume-expansion characteristics of the surrounding rock in the plastic stage were considered based on the secondary release displacement of surrounding rocks under the spatial effect of the excavation surface of the roadway.The interaction model of bolts and surrounding rocks was established under three typical working conditions of normal support,critical support,slip,and debonding to derive the analytical solution of the shear stress distribution of the axial force and the anchoring interface along the length of bolts.Besides,we systematically analyzed the effects of lagging support distance(support timing),expansion coefficients,bolt lengths,residual shear strength,and pallet reaction force on the force distribution of bolts.The research results showed that:(1)The internal force distribution of bolts conformed to the neutral point theory under normal support conditions.The axial force of bolts rose rapidly from the orifice along the bolt bodies,and it exhibited exponential attenuation towards the hole bottom after reaching its peak at the neutral point.The shear stress of the anchoring interface quickly attenuated from the maximum value to 0 in the part from the hole top to the neutral point,and it first increased and then decreased along the bolt body.Shear stress on both sides of the neutral point was in the opposite direction.The axial force of the bolt and the shear stress of the anchoring interface both decreased with the increased lagging support distance and increased with the increased expansion coefficients and bolt lengths.(2)The neutral point of the bolt was moved to the hole top under the critical working conditions of support.Axial force reached its maximum at the hole top and quickly attenuated to 0 along the bolt body to the hole bottom.The shear stress of the anchoring interface was distributed in an arched manner.The shear stress at both ends of the bolt body was 0,and the direction pointed to the hole bottom,which had a significant compressive stress effect on surrounding rocks.The earlier support timing and the larger bolt length were conducive to the rapid improvement of the anchoring force of bolts under weaker surrounding rocks.However,the bolt body was easy to break near the hole top.(3)The debonding range at the hole top was positively correlated with the expansion coefficients and bolt lengths and negatively correlated with residual shear strength under slip and debonding.As the ranges of slip and debonding increased,the neutral point was offset to the hole bottom.The shear stress distribution of the anchoring interface evolved into a bimodal curve.Axial force concentration was significantly reduced,and effective compressive stress on surrounding rocks was significantly reduced.The slip and debonding of the anchoring interface greatly weakened the load transfer capacity of the bolt body,which hindered the anchoring capacity of the bolt.Stress causing cracks on the anchoring interface could be transferred to the tray in time if a tray was applied,which suppressed slip and debonding.
作者
李英明
王想君
赵光明
孟祥瑞
刘刚
程详
LI Yingming;WANG Xiangjun;ZHAO Guangming;MENG Xiangrui;LIU Gang;CHENG Xiang(State Key Laboratory of Mining Response and Disaster Prevention and Control in Deep Coal Mines,Anhui University of Science and Technology,Huainan,Anhui 232001,China;Key Laboratory of Safe and Effective Coal Mining,Ministry of Education,Anhui University of Science and Technology,Huainan,Anhui 232001,China;Heilongjiang Ground Pressure and Gas Control in Deep Mining Key Laboratory,Heilongjiang University of Science and Technology,Harbin,Heilongjiang 150022,China)
出处
《岩石力学与工程学报》
EI
CAS
CSCD
北大核心
2023年第S02期3897-3912,共16页
Chinese Journal of Rock Mechanics and Engineering
基金
国家自然科学基金资助项目(52174102)
安徽省重点研究与开发计划项目(2022m07020007)
黑龙江省自然科学基金资助项目(LH2019E087)
关键词
岩石力学
全长锚固锚杆
空间效应
围岩峰后变形
中性点
锚杆内力分布
rock mechanics
full-length anchoring bolts
spatial effect
post-peak deformations of surrounding rocks
neutral point
internal force distribution of bolts
