Accurate modelling of the potential failure modes in the rock mass is an essential task towards a robust design of roof support systems in coal mines.The use of generalised rock mass properties based on averaged prope...Accurate modelling of the potential failure modes in the rock mass is an essential task towards a robust design of roof support systems in coal mines.The use of generalised rock mass properties based on averaged properties(e.g.Hoek-Brown model) has been found to limit the capability to reproduce the actual rock mass behaviour which may include a wide range of interacting and complex failure mechanisms such as shear and tension fracturing of the intact rock and shear and separation of pre-existing discontinuities,including re-activation.Recent studies have also shown that traditional models,such as the Mohr-Coulomb,may not accurately describe the behaviour of the intact rock,particularly for stress induced failures where spalling and slabbing are observed.This is mainly due to the cohesion and friction components of the shear strength of the intact rock not being mobilised at the same rate with strain-softening of the former component playing an essential role in the post peak behaviour.In addition,coal measure rocks are often transversely isotropic,both by way of the preferred orientation of clay particles within the finer grained lithology and by bedding textures and bedding partings,and this is often ignored in computer simulations.A newly developed transversely isotropic brittle rock mass model is applied in the simulation of a hypothetical and simple roadway development.A Cohesion Weakening-Friction Strengthening(CWFS) approach is adopted to describe the intact rock where the mobilisation and strain-softening of the two shear strength components are linked to plastic deformation.The impacts of anisotropy and brittle rock on the development of the excavation disturbed zone or height of softening,as often referred to,are investigated and their implication in the roof support design discussed.展开更多
The mechanism of bolt support is an important topic in mining engineering and slope treatment. The artificial material and loading system were self-developed to study the influence of bedding cohesion and bolt number ...The mechanism of bolt support is an important topic in mining engineering and slope treatment. The artificial material and loading system were self-developed to study the influence of bedding cohesion and bolt number on the anchoring behavior of bedded rock mass. The results show that, both peak strength and elasticity modulus increase gradually with the increase of bedding cohesion and bolt number. The axial stress–strain curve of bedded rock mass under the reinforcement of bolts presents the features of strain-softening and secondary strengthening. Finally, anchoring behavior of bedded rock mass with different bolt numbers was simulated by using FLAC3 D numerical program and the results were compared with the experimental results. This study can provide certain bases to the stability control and support design of bedded rock mass in roadway.展开更多
岩体的峰后强度对大型地下洞室群围岩开挖变形稳定具有较大影响。针对此问题,采用基于损伤的黏聚力弱化-摩擦角强化(cohesion weakening and friction strengthening, CWFS)模型并以动态链接库(dynamic link library, DLL)的形式植入FLA...岩体的峰后强度对大型地下洞室群围岩开挖变形稳定具有较大影响。针对此问题,采用基于损伤的黏聚力弱化-摩擦角强化(cohesion weakening and friction strengthening, CWFS)模型并以动态链接库(dynamic link library, DLL)的形式植入FLAC~(3D)程序中,针对依托工程的大型地下洞室群围岩开挖稳定性,开展考虑围岩开挖损伤和不考虑损伤的开挖全过程模拟。通过分析围岩的变形、应力、塑性区与损伤区的规律及其与现场监测数据的对比,研究开挖损伤对围岩稳定性的影响。结果表明:考虑围岩开挖损伤相对于不考虑损伤时,围岩应力释放程度较高,不利于地下洞室群的稳定;围岩塑性区和变形在主厂房顶拱与边墙等区域增加至1.5~2.0倍。CWFS模型能有效反映围岩塑性屈服的诱因,即损伤系数在0.5~1.0范围内为开挖卸荷导致的屈服,损伤系数在0~0.5范围内为开挖损伤导致的屈服;采用该模型得到的围岩开挖变形在量值上与采用多点位移计得到的现场监测值相近,变化趋势基本相同,不考虑围岩开挖损伤时得到分析结果相对于实际工程偏危险。展开更多
基金Project support from the Specialist Technical Apprentice Scheme from Coffey Geotechnics Ltd. Pty
文摘Accurate modelling of the potential failure modes in the rock mass is an essential task towards a robust design of roof support systems in coal mines.The use of generalised rock mass properties based on averaged properties(e.g.Hoek-Brown model) has been found to limit the capability to reproduce the actual rock mass behaviour which may include a wide range of interacting and complex failure mechanisms such as shear and tension fracturing of the intact rock and shear and separation of pre-existing discontinuities,including re-activation.Recent studies have also shown that traditional models,such as the Mohr-Coulomb,may not accurately describe the behaviour of the intact rock,particularly for stress induced failures where spalling and slabbing are observed.This is mainly due to the cohesion and friction components of the shear strength of the intact rock not being mobilised at the same rate with strain-softening of the former component playing an essential role in the post peak behaviour.In addition,coal measure rocks are often transversely isotropic,both by way of the preferred orientation of clay particles within the finer grained lithology and by bedding textures and bedding partings,and this is often ignored in computer simulations.A newly developed transversely isotropic brittle rock mass model is applied in the simulation of a hypothetical and simple roadway development.A Cohesion Weakening-Friction Strengthening(CWFS) approach is adopted to describe the intact rock where the mobilisation and strain-softening of the two shear strength components are linked to plastic deformation.The impacts of anisotropy and brittle rock on the development of the excavation disturbed zone or height of softening,as often referred to,are investigated and their implication in the roof support design discussed.
基金Financial provided by the National Key Research and Development Program of China (Grant No. 2017YFC0603001)the National Natural Science Foundation of China (Nos. 51734009 and 51704279)the Natural Science Foundation of Jiangsu Province (BK20170270)
文摘The mechanism of bolt support is an important topic in mining engineering and slope treatment. The artificial material and loading system were self-developed to study the influence of bedding cohesion and bolt number on the anchoring behavior of bedded rock mass. The results show that, both peak strength and elasticity modulus increase gradually with the increase of bedding cohesion and bolt number. The axial stress–strain curve of bedded rock mass under the reinforcement of bolts presents the features of strain-softening and secondary strengthening. Finally, anchoring behavior of bedded rock mass with different bolt numbers was simulated by using FLAC3 D numerical program and the results were compared with the experimental results. This study can provide certain bases to the stability control and support design of bedded rock mass in roadway.
文摘岩体的峰后强度对大型地下洞室群围岩开挖变形稳定具有较大影响。针对此问题,采用基于损伤的黏聚力弱化-摩擦角强化(cohesion weakening and friction strengthening, CWFS)模型并以动态链接库(dynamic link library, DLL)的形式植入FLAC~(3D)程序中,针对依托工程的大型地下洞室群围岩开挖稳定性,开展考虑围岩开挖损伤和不考虑损伤的开挖全过程模拟。通过分析围岩的变形、应力、塑性区与损伤区的规律及其与现场监测数据的对比,研究开挖损伤对围岩稳定性的影响。结果表明:考虑围岩开挖损伤相对于不考虑损伤时,围岩应力释放程度较高,不利于地下洞室群的稳定;围岩塑性区和变形在主厂房顶拱与边墙等区域增加至1.5~2.0倍。CWFS模型能有效反映围岩塑性屈服的诱因,即损伤系数在0.5~1.0范围内为开挖卸荷导致的屈服,损伤系数在0~0.5范围内为开挖损伤导致的屈服;采用该模型得到的围岩开挖变形在量值上与采用多点位移计得到的现场监测值相近,变化趋势基本相同,不考虑围岩开挖损伤时得到分析结果相对于实际工程偏危险。
