流变应力恢复法地应力测量的围岩初始应力解算理论

The rheological stress recovery method is especially proposed to measure the in-situ stress where the rock mass is soft at deep coalmine. Because of the rock rheology, the in-situ stress can be measured by burying the six-directional pressure transducer into the surrounding rock. This research focuses on two essential issues, including detailed classification of rock mass and related parameter selection, and the measuring performances of six-directional pressure transducer in rheological rock masses. The site rheological tests at deep coalmine would be carried out to reveal the time- dependent behavior of rock mass under high stress. A large number of rheological test data would be collected to analyze the relationship of rock grade and the rheological model and its parameters. Considering the rock mass rheology, the detailed classification of rock mass and corresponding parameter selection would be presented. The factors that affecting the measured stress of transducer would be investigated by solving the two-dimensional plane problem of rheological stress recovery method. Besides, the three-dimensional simulations of actual testing process would be carried out to reveal the performance of the factors. Further, the solving model would be proposed to describe the relation of measured stress of transducer and the initial stress of rock mass. On the basis of the detailed rock mass classification and the solving model, the soling theory of rheological stress recovery method would be developed and applied to engineering practice. This research provides the scientific theory support for the application of rheological stress recovery method in soft rock masses of deep coalmine.

流变应力恢复法是一种针对煤矿深部软弱围岩的地应力测量新方法，该方法基于软岩的强流变特性，采用钻孔埋设六向压力传感器的方式来实现围岩初始应力的测量。项目围绕“岩体细化分级及参数取值”和“流变岩体中六向压力传感器实测应力的演化规律”这两个关键科学问题开展研究。通过煤矿深部围岩原位流变试验，揭示不同等级围岩在高应力作用下的流变规律；大量收集岩体流变试验数据，分析岩体流变模型及参数与岩体等级之间的内在联系，提出考虑流变性质的岩体细化分级及参数取值方法。进而通过流变应力恢复法二维平面应变问题的求解以及测量过程的三维数值模拟，揭示影响六向压力传感器实测应力的主要因素及其影响规律。在此基础上，建立围岩初始应力与六向压力传感器实测应力间的关系模型，结合岩体细化分级及参数取值，形成流变应力恢复法的围岩初始应力解算理论并应用与工程实践。本项目研究成果能够为流变应力恢复法在深部软弱围岩中的应用提供理论支撑。

流变应力恢复法是一种针对煤矿深部软弱围岩的地应力测量新方法，该方法基于软岩的强流变特性，采用钻孔埋设六向压力传感器的方式来实现围岩初始应力的测量。项目围绕“岩体细化分级及参数取值”和“流变岩体中六向压力传感器实测应力的演化规律”这两个关键科学问题开展研究。主要研究成果如下：.（1）研制了原位岩体三轴流变试验设备。该试验设备主要包括加压稳压系统、位移测量装置和整体框架三部分。轴向最大加载力为15000kN，侧向最大加载力为500kN。制作了软弱岩体试样并开展了原位流变试验，结果表明：应力不高于加速蠕变应力阈值时，岩体试样有瞬时弹性应变，随后经历衰变蠕变阶段和稳定蠕变阶段；应力超过加速蠕变应力阈值时，岩体试样经历完整的衰减蠕变、稳定蠕变和加速蠕变三阶段并最终发生破坏。借助于分数阶微积分理论，建立了软弱岩体的非线性分数阶流变力学模型，并对试验数据分别进行了 Burgers 模型和非线性分数阶模型的参数拟合与对比分析。.（2）建立了流变应力恢复法的二维平面应变问题的理论模型，考虑Burgers和Boltzmann两种流变本构模型，推导了任意应力边界条件下岩体、注浆材料以及压力传感器应力分布的理论解，研究了影响压力传感器实测应力的主要因素。建立了基于六向压力传感器的流变应力恢复法地应力测试过程的数值计算模型，计算了不同围岩力学参数、不同地应力状态和不同注浆材料下的六向压力传感器所测恢复应力，分析了围岩力学参数、地应力状态和注浆材料模量对六向压力传感器的应力恢复规律的影响。在此基础上，建立了流变应力恢复法岩体初始应力解算模型。.（3）提出了流变应力恢复法的地应力测试流程，编制了流变应力恢复法地应力测试技术标准，并在河南平顶山矿区、安徽淮南矿区、青海鱼卡矿区等深部软岩巷道工程以及甘肃木寨岭、湖北黄家沟、云南东马场等软岩隧道工程中开展现场了工业性试验研究，检验理论研究的可靠性、可行性与实用性。