岩石峰后扩容特性的加卸载试验研究

【作者】 李林峰；

【导师】 侯克鹏； 余贤斌；

【作者基本信息】 昆明理工大学 ， 岩土工程， 2008， 硕士

【摘要】 地下工程岩体开挖是一个加载和卸载同时进行的复杂过程,人类对岩石在加卸载条件下的破裂过程和破裂后应力应变特性还没有足够的认识,搞不清楚围岩破裂带的形成和活动规律,对支架与围岩相互作用的力学变形规律不清楚,因此,研究岩石的扩容特征和变形破坏机理对把握巷道围岩变形机理及提出合理的支护设计具有较大的工程意义。本论文针对云南某矿山巷道围岩扩容破坏严重的实际情况,提出了三轴加载和卸围压试验方法,利用TAW-2000微机控制岩石伺服压力试验机,对岩石扩容特性、岩石变形破坏机理、岩石力学特性及其状态参数进行了试验研究。通过对试验结果的分析,主要得出以下重要结论:（1）在三轴加载和卸围压试验条件下,岩石扩容主要由较低围压（σ₃＜10MPa）条件下、达到轴向破坏应力以后的岩石破裂变形所产生;（2）在较低围压条件（σ₃＜10MPa）下,三轴加载试验过程中,试样以张性破裂为主;卸围压试验过程中,试样主要以剪切破裂为主。试样发生张性破裂时,比剪切破裂具有更大的岩石扩容;（3）卸载试验分析发现,岩石屈服破坏后,也表现出明显的塑性应变软化特性和剪切膨胀特性,这在现有研究卸荷力学特性的文献中还没有对其进行专门的论述;（4）与三轴加载试验相比,卸载试验条件下的岩石力学特性受围压影响更加显著（加载条件下,岩石单轴抗压强度σ_c为169.127MPa,岩性强度影响系数k为5.087;卸围压条件下,岩石单轴抗压强度σ_c为139.311MPa,岩性强度影响系数k为9.027。卸载条件下岩石单轴强度明显偏低,且围压对轴向破坏应力σ₁影响更为显著。）;（5）剪胀角与围压函数关系式是L.R.Aleiano和E.Alonso在加载试验结果中分析得到的,此次试验分析发现,卸围压条件下的剪胀角与围压也满足这一关系式;（6）论文最后在塑性应变软化和剪胀性的本构模型中引入剪胀角与围压函数关系式,使材料模型可以更加真实地模拟岩石扩容对岩石工程的影响。综上所述,论文通过三轴加载和卸围压试验,针对工程实际问题,从定性分析和定量分析两个角度,分别对岩石扩容特性及其破坏机理等进行了较详细的研究,得出了具有创新性的研究成果,对理论研究、工程设计和施工等具有一定的理论意义和工程价值。更多还原

【Abstract】 Excavation is a complicated process with loading and unloading at the same time in underground rock project, and the destruction process and the stress and strain of rock has not been sufficiently understond in loading and unloading conditions, and the formation and activity of rock rupture zone and the interactional law between frame and surrounding rock is also unclear. Therefore, the study of rock dilatancy and deformation failure characteristics has a great significance for understanding the deformation mechanism and reasonable supporting design of surrounding rock in roadway.In order to study the dilatancy of surrounding rock in some mine in Yunnan, the test methods were used, which include triaxial loading and unloading confining pressure, and the test was carried at the TAW-2000 microcomputer control servo rock compression testing machine. Eventually, the dilatancy characteristic, deformation failure mechanism, mechanics properties and mechanics parameters of rock has beenin-depth studied.By analysis of the experimental results, the important conclusions are as follows: （1） The dilatancy is mainly from deformation generated by the rock rupture in loading and unloading test, when the confining pressure less than 10MPa; （2） When the confining pressure less than 10MPa, specimens mainly occur extension breakage in the triaxial loading test, and specimens mainly occur shear breakage in the unloading confining pressure test. Extension fracture by comparison to shear breakage, bring more dilatancy; （3） The result’s analysis of the unloading confining pressure test showed that plastic strain-softening properties and dilatancy characteristics of rock can be also observed, which has not been specifically discussed in the literature published; （4） Compared with the triaxial loading test, the rock mechanical properties is significantly affected by confining pressure in the unloading test （In loading test, the uniaxial compressive strength of rock （σc） is 169.127MPa, and the lithology intensity influence coefficient k is 5.087; In unloading confining pressure test, the uniaxial compressive strength of rock （σc） is139.311MPa, and the lithology strength influence coefficient k is 9.027. So, the rock uniaxial strength is obviously on the low side in the unloading test condition, and the axial stress strength（σ₁） is affected confining pressure by all the more prominence.）; （5） The function between dilatancy angle and confining pressure is obtained by LR Alejano and E. Alonso in loading test, but the result of unloading test showed that dilatancy angle and confining pressure also meet the function in the unloading confining pressure test conditions; （6） Finally, the constitutive model which contain plastic strain-softening and dilatancy was improved by working in the function of dilatancy angle and confining pressure, so as to the effect of dilatancy in rock project can be more true in the simulation with the constitutive model.To sum up, the dilatancy that exist in rock engineering, was carried out a detailed study with the triaxial loading and unloading test, from the qualitative analysis to quantitative analysis. And the innovative research results has great theoretical significance and engineering value for theoretical studies, engineering design and construction.更多还原