【作者】 张茂林；

【导师】 靖洪文；

【作者基本信息】 中国矿业大学 ， 岩土工程， 2013， 博士

【摘要】 断续节理岩体的破裂演化及锚固控制是岩体力学与工程界研究的热点与难点问题之一,尽管现有的研究成果取得了许多进展,但仍存在大量难题未得到合理解决。本文结合国家自然科学基金项目(51074162,51179189),采用物理模型、数值计算、理论分析与现场验证等研究方法,深入系统地对断续节理岩体破裂演化特征及锚固控制机理这一科学问题进行了研究。主要研究成果与结论如下：(1)研制了大尺度(500mm×500mm×480mm)的三维岩体锚固模拟试验系统,该系统具有完备的加载、约束及量测功能,能够真实再现岩体试件的加载、变形及破坏的全过程,同时通过自行研制的高精度微型锚杆端部测力计及光纤光棚测力锚杆,可以实现在试验过程中对锚杆受力全过程进行实时监测；设计了多组节理的制作方法,并成功的制作了模具；研制了较为理想的模拟断续节理岩体的相似材料,具有组分简单、力学性能稳定、参数可调、无毒无污染、价格低廉等优点。(2)通过对断续节理岩体的单轴压缩试验,获得了无锚断续节理岩体的破裂演化规律：峰值强度、极限应变和峰后0.7σc时的试件中部核心承载区宽度,均随节理倾角的增大先减小后增加；次生裂隙的起裂位置主要是试件的四周,且以张开型和拉剪型裂隙为主起裂应力随节理倾角呈线性增加关系；节理倾角为60°时的岩体单位体积破坏所消耗的能量最小,小于60°时,角度越小消耗的能量越大,反之则相反；节理倾角小于45°时,岩桥主要以张拉破坏和拉剪破坏为主,随着倾角的增大,岩桥发生剪切破坏的比例增加；低角度(0°≤α＜45°)节理岩体主要以拉伸或拉剪破坏为主,高角度(α≥45°)沿预制节理面剪切破坏。(3)采用研制的试验系统,对不同倾角的断续节理岩体进行模拟试验研究,发现了锚固体的强度主要由岩体的强度、锚杆预紧力引起的初始等效约束应力(σ3i)以及锚杆变形过程中产生的等效约束应力(σ3b)所贡献的强度组成；建立了岩体峰值强度、残余强度与裂隙倾角、锚杆密度之间的函数关系式,并成功用于巷道工程设计,取得了良好的效果。σρ=4.543+1.412ρ-2.146ρ2+1.564ρ3-0.02146α-8.006×10-4α2+1.307×10-5α3σR=3.624+2.039ρ-2.263ρ2+1.499ρ3-0.005564α-1.41×10-4α2+2.267×10-6α3(4)研究了锚固体的弹性模量、泊松效应及体积应变与加锚密度、预制节理倾角之间的关系：即弹性模量随加锚密度总体呈非线性增长；同一倾角情况下应力峰值时的广义泊松比与水平方向应变随锚杆密度增大而增大；岩体的强度峰值点与体积膨胀起始点并不完全一致,多数情况下岩体强度峰值滞后于体积应变峰值；锚杆可明显抑制剪切破坏的发生,但对拉伸破坏的抑制作用偏弱。(5)分析了锚杆的受力演化及分布特征,揭示了全长锚固锚杆的群锚机理：低密度锚杆主要由杆体的中外段承载,自身受力和对围岩的约束力都存在明显的分布不均现象锚固体容易出现薄弱的关键部位,而高密度锚杆能充分调动杆体内锚段的承载性能,改善每根锚杆和围岩的受力状态。更多还原

【Abstract】 Research on the fracture evolution and bolting of intermittently jointed rocks is one of thehotspots and difficulties in the field of rock mechanics and rock engineering. Although someprogresses were made by scholars in this field, there are still many problems that need to besolved properly. Funded by the National Natural Science Foundation of China (51074162,51179189) and using physical simulation, numerical simulation, theoretical analysis and otherresearch methods, this paper made an in-depth study on the fracture evolution characteristics andbolting mechanism of intermittently jointed rocks. The main research findings and conclusionsare as follows:(1) A large-scale (500mm×500mm×480mm) three-dimensional testing system wasdeveloped for the simulation of rock bolting. This system has functions of loading, confining andmeasurement, with which the whole process of loading, deformation and failure of jointed rockscan be truly represented. To monitor the real-time anchoring force of bolt, the high-precisionminiature ergometer was developed to measure the anchor end force and the dynamometric boltbased on fiber Bragg grating was made to get the multipoint anchoring force along bolt. A newmethod of making multiple joints was designed and the corresponding molds were fabricated.An ideal similar material of intermittently jointed rocks was developed, which has advantages offew components, stable mechanical properties, adjustable parameters, pollution-free, low priceand so on.(2) Fracture evolvement rules of intermittently jointed rocks without bolt were obtained byuniaxial compression tests. The peak strength, ultimate strain and the center bearing core widthof rocks at post-peak stress of0.7σcdecrease first and then increase with the rise of joint angles.The initiation position of secondary cracks is mainly at the periphery of specimen, and most ofthe cracks are tensile or tensile-shear cracks. The crack initiation stress increases linearly withjoint angles. The energy consumed by the destruction of unit volume rocks is the minimum whenthe joint angle is60°; the energy increases with the decrease of joint angle when it is less than60°, and with the increase of joint angle when it is greater than60°. The failure of rock bridges ismainly due to tension and tensile-shear cracks when the joint angle is less than45°. The ratio ofshear cracks increases with the rise of joint angle. The main fracture types of jointed rocks are oftension and tensile-shear fractures when the joint angle is less than45°, and the rocks tend toshear along the joint surfaces when the joint angle is larger than45°.(3) Model experiments were made on the intermittently jointed rocks with different jointangles under various bolting parameters by using the self-developed testing system. It was foundthat the strength of bolted rocks comprises the strength of rocks, the additional strength caused by both initial equivalent constraining stress (σ3i) which is aroused by pre-tension force of bolts and the equivalent constraining stress (σ3b) which is generated by deformation of bolts. The functional relations among peak strength and residual strength of bolted rocks, joint angle and bolting density were established and successfully used in the design of bolting parameters for a tunnel, through which good effects were achieved.σp=4.543+1.412/ρ-2.146/ρ2+1.564/ρ3-0.02146a-8.0×0610α2+1.307×105α3σR=3.624+2.039ρ-2.263ρ2+1.499ρ3-0.005564a-1.41x10-4a2+2.267×10-6α3(4) The relations between the elastic modulus, Poisson’s ratio, volumetric strain of bolted rocks and the bolting density, the joint angle were obtained. The elastic modulus grows nonlinearly with the bolting density. The generalized Poisson’s ratio and the horizontal strain at the peak stress grow with the bolting density for the same joint angle. In general, the position of peak strength of bolted rocks is not the same as the beginning point of volume expansion. In most instances, the peak strength lags behind the volume expansion point of the bolted rocks. Bolts can obviously inhibit shear fracture, but has less effect on tensile fracture.(5) The function mechanism of full-length anchoring bolts was revealed by analyzing the evolution and distribution characteristics of bolting force. For sparsely distributed bolts, the force distribution along each bolt is uneven and the force of its central and external sections is much greater than that of internal section in the whole lifetime of the bolt. Consequently, the constraining force of bolts on rocks is unevenly distributed and some weak parts are prone to occur, which is adverse to the stabilization of the rocks. For densely distributed bolts, the force distribution along each bolt is nearly uniform. It can fully mobilize the load-bearing capacity of each bolt and improve the stress state of bolts and rocks. Therefore, it is more conducive to the stability of bolted rocks.更多还原