【作者】 李伟；

【导师】 梁正召；

【作者基本信息】 大连理工大学 ， 岩土工程， 2022， 硕士

【摘要】 裂隙在岩体中分布广泛,岩体节理或裂隙在很大程度上会影响岩体的物理与力学性质。在隧道、边坡、矿山巷道等裂隙岩体工程中开挖施工时,节理或裂隙的存在使岩体卸荷作用更加明显,可能会引发一系列工程地质灾害,例如岩爆、滑坡与突水等,因此研究卸荷作用下的裂隙扩展机制是至关重要的。目前,有关岩体裂隙扩展机制的研究,学者们大多聚焦于单轴或三轴压缩试验,已有的卸荷试验多针对无裂隙岩体开展的物理试验,并且针对卸荷作用下的岩体裂隙扩展机制的相关机理研究还不够完善,所以研究卸荷条件下岩体裂纹扩展机理以及破坏模式具有重要的科学价值与工程意义。本文基于岩体破裂过程分析软件RFPA^3D,在考虑岩体非均匀性的基础上,分别模拟研究了含单裂隙岩体的双轴加卸荷试验、真三轴卸荷试验与含断层隧道围岩的稳定性问题,探究卸荷应力路径、卸荷方向、中间主应力大小、裂隙与断层倾角等多种因素影响下岩体裂隙的扩展机制与围岩安全性问题。具体分为以下三方面:（1）基于RFPA^3D模拟研究含单裂隙岩体的双轴加卸荷数值模拟试验。首先基于RFPA软件进行数值模型验证;其次采取三种不同卸荷应力路径的卸荷方案,对含不同倾角裂隙的岩体试样模型进行加卸荷试验直至模型破坏,探究卸荷应力路径以及裂隙倾角对岩体裂纹扩展机制的影响规律。结果表明,三种卸荷应力路径对岩体裂隙扩展机制的影响排序为:增轴压降侧压>恒轴压降侧压>增轴压恒侧压;卸荷条件下,裂隙倾角越大,裂隙起裂强度及模型破坏峰值强度越大。研究结果表明,实际开挖工作中选择合适的卸荷应力路径至关重要。（2）基于RFPA^3D模拟研究含单裂隙岩体的真三轴卸荷数值模拟试验。首先在设定的两种真三轴应力状态下分别降低中间主应力和最小主应力,探究应力卸荷方向对岩体裂隙扩展机制的影响规律;其次在中间主应力方向平行于裂纹面的条件下,设定不同中间主应力值后降低最小主应力,探究中主应力大小对岩体裂纹扩展机制的影响规律。结果表明,卸荷条件下,当卸荷方向平行于裂纹面时,裂纹更不容易发生萌生和扩展,岩体也更不容易发生突然的脆性破坏;当中间主应力方向平行于裂纹面并降低最小主应力时,中主应力大小对卸荷条件下的岩体影响不大。研究结果表明,实际工程中,应该预先确定岩体主要结构面的位置,尽量在平行于结构面的方向进行开挖卸荷工作。（3）基于RFPA^3D模拟研究含断层隧道的围岩稳定性问题。以锦屏二级深埋隧洞的构造性岩爆为例,结合实际工程背景,采用RFPA^3D强度折减版软件,在断层走向与隧道走向垂直的情况下,于隧道前方设置不同倾角（15°、30°、45°、60°）的断层,通过强度折减法得到不同断层倾角的情况下隧道围岩的安全系数,探讨研究不同倾角的断层对隧道围岩稳定性的作用规律。结果表明,当断层走向垂直于隧道走向时,断层倾角越大,安全系数就越大,隧道稳定性就越高。研究结果表明,当断层与隧道呈大角度相交时,隧道围岩相对会更加稳定,施工也会更加安全。更多还原

【Abstract】 It is widely distributed in fractured rock mass,and the joints or fissures of rock mass will affect the physical and mechanical properties of rock mass to a great extent.In the excavation of tunnel,slope,mine roadway and other fractured rock mass projects,the existence of joints or fissures makes the unloading effect of rock mass more obvious,which may lead to a series of engineering geological disasters,such as rock burst,landslide and water inrush,etc.Therefore,it is essential to study the crack propagation mechanism under the unloading effect.At present,scholars mostly focus on uniaxial or triaxial compression tests,and the existing unloading tests are mostly physical tests on rock mass without cracks,and the research on the mechanism of rock mass crack propagation under unloading is not perfect enough,so it is of great scientific value and engineering significance to study the crack propagation mechanism and failure mode of rock mass under unloading conditions.In this paper,based on the software RFPA^3D,considering the heterogeneity of rock mass,the biaxial loading and unloading test,true triaxial unloading test of rock mass with single crack and the stability of surrounding rock of tunnel with fault were simulated,and the propagation mechanism of rock mass crack and the safety of surrounding rock under the influence of unloading stress path,unloading direction,intermediate principal stress,dip angle of crack and fault were explored.It is divided into the following three aspects:（1）Numerical simulation test of biaxial loading and unloading of rock mass with single crack based on RFPA^3Dsimulation.Firstly,the numerical model was verified based on RFPA software.Secondly,three unloading schemes with different unloading stress paths were adopted,and loading and unloading tests were carried out on the rock mass sample model with cracks with different inclination angles until the model was destroyed,so as to explore the influence of unloading stress paths and crack inclination angles on the crack propagation mechanism of rock mass.The results showed that the influence of three unloading stress paths on the crack propagation mechanism of rock mass was as follows:increasing axial pressure drop lateral pressure>constant axial pressure drop lateral pressure>increasing axial pressure constant lateral pressure;Under unloading condition,the greater the crack inclination angle,the greater the crack initiation strength and the peak strength of model failure.The results show that it is very important to choose the appropriate unloading stress path in actual excavation.（2）Numerical simulation test of true triaxial unloading of rock mass with single fracture based on RFPA^3Dsimulation.Firstly,the intermediate principal stress and the minimum principal stress were respectively reduced under two set true triaxial stress states,and the influence of stress unloading direction on the crack propagation mechanism of rock mass was explored.Secondly,under the condition that the direction of the intermediate principal stress was parallel to the crack surface,the minimum principal stress was reduced by setting different values of the intermediate principal stress,and the influence of the magnitude of the intermediate principal stress on the crack propagation mechanism of rock mass was explored.The results showed that under the unloading condition,when the unloading direction was parallel to the crack surface,the crack was less prone to initiation and propagation,and the rock mass was less prone to sudden brittle failure.When the direction of the intermediate principal stress was parallel to the crack surface and the minimum principal stress was reduced,the magnitude of the intermediate principal stress had little effect on the rock mass under unloading conditions.The results showed that in practical engineering,the position of the main structural plane of rock mass should be determined in advance,and the excavation and unloading work should be carried out in the direction parallel to the structural plane as far as possible.（3）Study on the stability of surrounding rock of tunnel with fault based on RFPA^3Dsimulation.Taking the structural rockburst of Jinping II deep-buried tunnel as an example,combined with the actual engineering background,using RFPA^3Dstrength reduction software,the faults with different dip angles（15°,30°,45°,60°）were set in front of the tunnel when the fault strike was perpendicular to the tunnel strike,and the safety coefficient of the tunnel surrounding rock with different dip angles was obtained by strength reduction method,and the action law of the faults with different dip angles on the stability of the tunnel surrounding rock was discussed.The results showed that when the fault strike was perpendicular to the tunnel strike,the greater the fault dip angle,the greater the safety factor and the higher the tunnel stability.The results show that when the fault intersects the tunnel at a large angle,the surrounding rock of the tunnel will be relatively more stable and the construction will be safer.更多还原