【作者】 朱杰兵；

【导师】 刘泉声； 冯夏庭；

【作者基本信息】 中国科学院研究生院（武汉岩土力学研究所） ， 岩土工程， 2009， 博士

【摘要】 由于西部水电工程大都具有大埋深、超高地应力、超高外水压力特点,硐室围岩体的力学响应明显有别于浅部岩体,如何保证地下工程围岩稳定性及衬砌支护结构的合理性是迫切需要解决的关键科学问题。基于此,本论文以锦屏二级水电站辅助洞开挖及运行期稳定性分析为研究背景,选取砂岩洞段为对象,围绕高地应力及卸荷等外部条件,系统研究其在卸荷条件下的瞬时力学响应以及长时流变特性。通过较为系统的试验研究、理论分析以及数值仿真等手段,研究岩石材料的变形破坏与时间的演化规律,进而建立反映工程岩体长期变形特点的非线性粘弹塑流变本构模型。基于所建立的本构模型,对锦屏二级电站交通辅助洞开挖及运行过程进行数值模拟,研究工程岩体的应力和位移的变化规律以及围岩的长期稳定性,并结合现场实测数据开展相应的工程验证工作。总体上,本论文的主要研究内容包括:（1）从工程现场取回典型砂岩,加工成标准试件Φ50mm×100mm,采用MTS815.03电液伺服压力试验机,对砂岩进行常规的单轴实验、高应力下三轴压缩试验,分析了岩样的变形特点、强度特征、脆延转换规律及破坏模式,探讨了围压与变形模量、围压与峰值应变的关系。通过高孔隙水压下的三轴渗透试验,研究高渗透压差条件下渗透率与轴向应变、渗透率与围压之间的变化规律及渗透水压力对岩石强度的影响。这些有益的成果为进一步开展岩石卸荷试验及理论研究提供了基础依据。（2）采用MTS815.03电液伺服压力试验机,对砂岩开展了三轴卸围压破坏试验,三轴卸围压渗透试验等,研究了不同卸荷路径下砂岩的变形特征,并结合SEM测试微观分析方法,对岩石的断口破坏模式及破坏机理进行了探讨。基于高应力下卸围压三轴试验,获得了不同卸荷方式下岩石的强度、变形特征及其与围压之间的关系,推导了卸荷过程中岩石变形模量损伤演化方程。基于三轴卸荷渗透试验,探讨了卸荷渗透率与轴向应变、渗透率与围压间的变化规律等。（3）在大量的加载和卸载三轴试验的基础上,开展了岩石卸荷条件下的本构模型及非线性强度准则方面的研究。基于试验曲线,假定岩石的屈服强度、峰值强度、残余强度和围压呈线性关系前提下,建立了双线性弹性—线性软化—残余理想塑性模型。通过不同应力水平、应力路径下的试验强度特性分析,建立砂岩卸载条件下幂函数型非线性Mohr强度准则。基于该准则,研究了加荷、卸荷及高孔隙压力卸荷等条件下强度参数的差异性。（4）采用TLW-2000型岩石流变仪,开展了砂岩三轴卸围压流变试验,研究了不同卸荷差应力水平对砂岩蠕变特性的影响。系统分析了轴向应变与侧向应变、塑性变形与蠕应变、蠕变速率等变化规律,为建立岩石卸荷条件下流变本构模型提供依据。（5）基于三轴卸荷条件下的流变试验成果,采用Bugers模型及改进的非线性损伤Bugers模型,以残差平方和为目标函数,利用嵌入Levenberg-Marquardt算法的最小二乘法（LM-NLsF法）对Buyer’s流变模型及改进的损伤Bugers模型参数进行了辨识,建立了非线性损伤粘弹塑性本构模型。（6）将改进的非线性损伤粘弹塑性本构模型在FLAC^3D中通过二次开发予以实现。并应用于锦屏二级电站交通辅助洞A、B洞开挖卸荷的瞬时力学响应及其围岩时效变形分析,研究了隧洞开挖后的蠕变特征及损伤演化过程,并将时效变形数值分析结果与现场监测结果比较,以验证所建立的非线性损伤粘弹塑性本构模型的正确性及合理性。更多还原

【Abstract】 Inasmuch as hydroelectric projects in West China is being encountered challenges of deep depths,extra-high geostress and extra-high hydraulic pressure etc.,the mechanical response of the deep rock masses shows observable distinctions from that of shallow part.It is a key scientific issue how to ensure stability of surrounding rock masses and desirability of lining structure ater excavation.In this point,on the background of excavation and operation of subsidiary tunnels of JinPingⅡhydropower station,a representative tunnel section with sandstone strata,chosen as research objective,is investigated.Via methods of experimental researches,theory analysis and numerical simulation,the instantaneous deformation and strength properties as well as its rheological properties of sandstone are explored systematically,and a nonlinear damage viscoelastic-plastic constitutive equation is established which can reflect nonlinear deformation and creep properties of sandstone. Furtherly,a serial of numerical analysis are performed on simulating of mechanical response and its time-depended deformation after excavation of subsidiary tunnels based on the experimental and theoretical results achieved in this paper.It is shown that the computational results are in good accordance with the data observed on site.The main research works included in the dissertation are as following:The typical sandstones were sampled from engineering site and machined as standard specimens of 50mm in diameter and 100mm in length.By using MTS815.03 rock mechanics test system,both conventional uniaxial & triaxial tests and triaxial permeability tests under high confining pressure are conducted systematiacally.Based on the experimental results of uniaxial & triaxial tests,the deformation feature,strength characteristic,brittle-ductile transition laws and failure modes are analyzed in detail. Moreover,the relationship between peak strain,secant modulus and confining pressure are also discussed.By analyzing experimental results of triaxial permeability tests,the varying characteristics,including permeability versus axial strain,permeability versus confining pressure and seepage pressure versus rock strength,are obtained.Therefore,the meaning conclusions can provide foundational scientific evidence for further experimental and theoretical research in terms of rock mechanics.By using MTS815.03 rock mechanics test system,unloading triaxial tests,unloading triaxial permeability tests and SEM fracture scanning are performed on representative sandstone.The deformation characteristic are researched under different test conditions and unloading paths.Combining micro analysis methods,failure characteristic and failure mechanism are discussed.With the experiment of unloading triaxial tests of sandstone, relationship between the deformation feature,strength characteristic and failure mechanism and confining pressure under different unloading paths are discussed,and the equation for damage evolution derived subsequently.By experiments of unloading triaxial permeability tests,the varying characteristics under unloading conditions,including permeability versus axial strain,permeability versus confining pressure and seepage versus rock strength etc, are obtained.By SEM fracture scanning,micro failure mechanism and damage evolution laws,caused by unloading,are investigated lastly.Based on above data of loading and unloading triaxial experiments,constitutive model and strength criterion are investigated.In view of the complete stress-strain curves of sandstone under unloading condition,assuming that the relation between yield strength, peak strength and residual strength is linear,the bilinear elastic-linear strain softening-residual ideal plastic model is put forward.By analyzing strength characteristics under high confining pressure and high seepage pressure,exponential functional Mohr strength criterion is also established,and furtherly,the difference of strength parameters under loading paths,unloading paths and combining with high seepage pressure,are explored.By using TLW-2000 servo-controlling rheology tester,the unloading confining triaxial rheological tests are performed.Detailed investigations are made to the effect of different unloading stress levels on the creep properties,and the variation of the axial strain,lateral strain,plastic strain and strain rate are studied.The test results provide foundational materials for the establishment of sandstone’s creep models.Based on the above data of unloading confining pressure creep tests,Burger’s model and nonlinear rheological damage Burger’s model are selected to describe the properities. By taking the sum square of survival difference as optimization objective,and the least square embedded in Levenberg-Marquardt algorithm is adopted to optimize the fitting parameters of models.And then,nonlinear damage viscoelastic-plastic rheological constitutive model is established.By programming the creep constitutive model,numerical simulations method is achieved in Flac^3D.Numerical analysis about subsidiary tunnels of JinPingⅡhydropower station,which emphasize instantaneous and secular deformation behavior caused by excavation,are carried out.The computational results,comparing with the data observed on site,validate that the numerical procedure of rheological model is reasonable and correct.更多还原