冲击条件下深部巷道围岩-液压支架系统破坏及稳定性的数值分析及应用

Most of coal bumps or rockbursts take place at tunnels, exceeding 70 percent of the total. At present, a good performance of defense against tunnel coal bumps has been achieved prelimanarily in some coal mines due to the use of tunnel hydraulic powered supports, such as in Yuejin, Zhaizhen, Huating and Laohutai mines. However, for hydraulic powered supports, numerical models considering three typical stages of working resistances, i.e., an increasing stage, followed by a constant stage, and then a decreasing stage, have not been reported so far; it is still unclear that the interaction mechanism between hydraulic powered support and tunnel surrounding rock at depth; and for the system of tunnel surrounding rock and hydraulic powered support, no study of the capacity of defence against coal bumps has been carried out. In this proposal, a hydraulic powered support is seen as a structure composed of two kinds of elements: ordinary elements modeling the metallic beam and base, etc, and special elements modeling complex behaviors of liquid with high pressures. During the increasing mining pressure or impact process, a constitutive model for the specical element will be developed by use of C++ considering the three features of variant working resistances, and implemented in FLAC3D. Under the impact condition, the further failure and instability of the supported tunnel surrounding rock where rockburst notches, slabbing and zonal disintegration have been occurred under quasistatic and excavating conditions, will be investigated. Accuracy of numerical models at different scales will be checked through calculating the strain and displacement fields at a labortory scale using a developed digital image correlation method for larger strains, and through measuring stress and displacement in tuunel surrounding rock in situ. For the system composed of tunnel surrounding rock at depth and hydraulic powered support, a reliable method to calculate the capacity of defense against tunnel coal bumps will be proposed at the end and applied in coal mines, providing technical supporting for strata stability control.

巷道冲击地压占冲击地压总数的70%以上。巷道液压支架（支架）的良好防冲效果已在跃进、翟镇、华亭、老虎台等煤矿得到初步检验，但目前，能反映支架增阻、恒阻及降阻3阶段特点的数值模型尚未见报道，其与深部巷道围岩的相互作用机制并不清楚，巷道围岩-支架系统的抗冲击能力研究尚未见开展。本项目拟将支架视为由模拟顶梁、底座等的常规单元和模拟高压液体复杂行为的特殊单元构成，针对来压或冲击过程中，支架工作阻力变化的3阶段特点，利用C++开发特殊单元的本构模型，并嵌入FLAC3D中，研究在静载或采动条件下已发生岩爆坑、板裂化及分区破裂化的支架支护巷道围岩在冲击条件下的继续破坏及失稳规律，通过自主开发的适于变形较大情形的数字图像相关方法计算实验室尺度模型的应变、位移场，通过现场巷道围岩的应力或位移测试，检验数值模型的准确性。最终形成可靠的深部巷道围岩-支架系统抗冲击能力的计算方法，并用于实践，指导围岩稳定性控制。

在试验方面，提出了巷道围岩模型的批量制备方法，研制了一种平面应变巷道围岩模型内、外压加载装置及观测系统，可为巷道围岩破坏及失稳的机理研究及巷道冲击地压的预测防治提供大量的可靠数据。系统开展了70余个实验室尺度巷道围岩模型变形破坏过程的试验研究，研究了内压（作用于巷道表面，模拟液压支架的支护阻力）、围压和垂直方向加载速度的影响。深入开展了由低液限黏土（用于制作巷道-围岩模型）制成的长方体试样变形破坏过程中应变、损伤变量、主应变轴偏转角的统计分析，深化了对黏土变形破坏过程的认识。在算法方面，系统开展了有利于提高数字图像相关方法在剪切带测量方面的精度和扩大适用范围的研究，提出了一种应变场声发射事件时空强的测量方法，提出了一种变形数字图案的复原方法，提出了两种构形条件下岩土试样剪切带倾角演变规律的观测方法，提出了一种基于半子区分割法的数字图像相关方法，提出了一种应变局部化带间距演变规律的多维同步优化测量方法。在数值方面，利用FLAC-3D的2次开发方法和自主开发的适于固体连续介质向非连续介质转化的连续-非连续方法，系统开展了巷道围岩模型变形破坏过程的数值模拟研究。对于二维模型，主要研究了剪切带形成过程中能量释放规律和围岩变形-开裂-垮塌过程，加载方式包括位移控制加载、等幅值半正弦（冲击）波加载和衰减幅值半正弦波加载等；采用服从弹性-理想塑性本构模型的若干单元模拟液压支架；巷道形状包括圆形和正方形。对于三维模型，主要研究了轴压与侧压之比及非均质度对深部巷道围岩分区破裂化的影响。对于液压支架支护的巷道围岩模型，研究发现，前几次冲击波对围岩的破坏较严重；波幅越大，围岩破坏越严重，岩石单元弹射现象越明显。初步研究了支护阻力及支护时机的影响。此外，还采用自主开发的连续-非连续方法模拟了不同条件下（巴西圆盘劈裂、直接拉伸和紧凑拉伸等）岩样变形-开裂过程，展现了该方法的强大功能和广泛应用前景。