软岩硐室群蠕变模型选择与长期稳定性研究

Study on Creep Model Selection and Long-term Stability of Soft Rock Chamber Group

硐室服务年限较长,围岩会随着时间的积累而产生蠕变,造成支护变弱甚至失效,从而影响矿山安全。为研究工程软岩硐室围岩的蠕变特性,以钟九铁矿井底硐室群为研究对象,首先采用ROCK1000-50VHT型岩石高温三轴流变试验系统进行5、10、15 MPa围压下的三轴蠕变试验,分析其蠕变和破坏特征。试验结果显示:闪长岩蠕变破坏在低围压下主要为剪切破坏,当围压逐渐增大时,会转变为劈裂破坏;在三轴应力条件下,闪长岩的蠕变会出现压密、弹性、裂隙扩展和破坏4个阶段;当加载应力较低时,闪长岩在瞬时应变后会出现等速蠕变,随后轴向应变逐渐趋于稳定;但当加载应力较高时,岩体进入到等速蠕变阶段的时间变长,轴向应变不断增大。根据其蠕变特征选取Burgers模型建立本构方程,经拟合后与蠕变试验曲线基本吻合,表明本构模型能够反映闪长岩蠕变力学特性。最后采用Burgers蠕变本构模型,基于FLAC3D对硐室支护模型进行数值模拟。结果表明,现有支护方案可以保持硐室群的长期稳定性。研究对软岩硐室群支护时效性分析具有借鉴意义。

The service life of the chamber is long,and the surrounding rock will creep with the accumulation of time,resulting in weakening or even failure of the support,thus affecting the safety of the mine.In order to study the creep characteristics of surrounding rock of engineering soft rock chamber,the bottom chamber group of Zhongjiu Iron Mine was taken as the research object.Firstly,the high temperature triaxial rheological test system of ROCK1000-50 VHT rock was used to carry out the triaxial creep test under the confining pressure of 5 MPa,10 MPa and 15 MPa,and the creep and failure characteristics were analyzed.The test results show that the creep failure of diorite is mainly shear failure under low confining pressure.When the confining pressure increases gradually,it will be transformed into splitting failure.Under the condition of triaxial stress,the creep of diorite will have four stages:compaction,elasticity,crack propagation and failure.When the loading stress is low,the diorite will have constant creep after the instantaneous strain,and then the axial strain gradually tends to be stable.However,when the loading stress is high,the time for the rock mass to enter the constant creep stage becomes longer,and the axial strain increases continuously.According to its creep characteristics,the Burgers model is selected to establish the constitutive equation.After fitting,it is basically consistent with the creep test curve,indicating that the constitutive model can reflect the creep mechanical properties of diorite.Finally,the Burgers creep constitutive model is used to simulate the chamber support model based on FLAC3D.The results show that the existing support scheme can maintain the long-term stability of the chamber group.The research has reference significance for the timeliness analysis of soft rock chamber group support.