摘要
研究巷道(隧道)围岩的开挖卸荷效应的有效途径之一是进行小型围岩试件的开挖卸荷试验。为便于制备和掌控小型围岩试件的强度,首先选用高强石膏类材料进行了配比试验,获得了试件强度范围5~20 MPa所对应材料的配比,研究各相似材料成分对试件强度的影响规律。其次制作、加工了小型围岩试件(高290 mm、内径为100 mm、外径为200 mm厚壁圆筒型)。采用具有自主知识产权的巷道围岩开挖卸荷模型试验系统,对小型围岩试件进行了缓慢开挖卸荷和破坏的模拟试验。开挖卸荷过程在力学原理上可以模拟实际工程的开挖条件,即先对围岩试件施加轴压、外压和内压,以模拟原岩应力。开挖(即卸荷)时,卸载内压,保持其他两向压力不变。试验过程中采集到围岩试件轴向和切向两个方向的应变数据,获得了开挖卸荷全过程的应变–时间曲线及应变随内外压差的变化关系。试验结果表明,轴向应变和切向应变随卸荷幅度加大而逐渐增大,而且呈现内侧应变大于外侧,试件在卸荷过程中向内膨胀;同一测点其切向应变大于轴向应变。卸荷破坏时围岩试件破坏发展路径朝向洞内即沿径向发生破坏,破坏形态呈现分层破裂现象。
One of the effective ways to study the excavation and unloading effect of roadway(tunnel) is to carry out excavation and unloading test of small-scale rock specimen. In order to make it easier to prepare and control the strength of the small surrounding rock speimens, firstly the high-strength gypsum-based materials are selected to carry out the ratio test. The proportion of the corresponding materials with the strength range of 5-20 MPa and the influence of the similar materials composition on the strength of the specimen is obtained. Secondly, a small wall rock specimen(thick wall cylinder type: 290 mm high, 100 mm with diameter, 200 mm outer diameter) is processed. The tunnel excavation unloading model test system with independent intellectual property rights has been used to simulate the unloading and failure of the surrounding rock specimens. The excavation unloading process can simulate the excavation conditions of the actual engineering on the principle of mechanics; that is, the axial compression, external pressure and internal pressure are applied to the surrounding rock specimen to simulate the original rock stress. Excavation(that is, when unloading), unloading the internal pressure and keep the other two pressure constant. During the test, the relationship between the strain in two directions along the axial direction and the tangential direction of the surrounding rock specimen is collected. The strain-time curve and the relationship between the strain and the pressure drop are obtained. And present: the inner strain is larger than the outer one and the specimen expands inward during unloading; at the same measuring point the tangential strain is larger than the axial strain playing a leading role. When the unloading damage occurs, the failure direction of the surrounding rock specimen destroys toward the inside of the cave, that is, along the radial direction. Failure pattern presents stratified rupture.
出处
《岩土力学》
EI
CAS
CSCD
北大核心
2018年第S1期159-166,共8页
Rock and Soil Mechanics
基金
国家自然科学基金面上项目(No.51574247)
国家自然科学基金委员会煤炭联合基金重点支持项目(No.U1361210)~~
关键词
高强石膏材料
配比试验
模型试验
小型围岩试件
开挖卸荷
围岩变形
high strength gypsum material
mixture ratio test
model test
small surrounding rock specimen
excavation unloading
surrounding rock deformation
