本文選題：軟巖　切入點：地下洞室　出處：《武漢大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：隨著我國經(jīng)濟(jì)的快速發(fā)展和城市化的推進(jìn),水利、能源、交通、國防等基礎(chǔ)設(shè)施建設(shè)更多地涉及地下空間開發(fā),地下工程施工面臨更多新挑戰(zhàn)、新問題,軟巖地下洞室長期穩(wěn)定往往是工程能否順利完成的關(guān)鍵。本文以云南省滇中引水工程鳳屯隧洞為依托,從軟巖流變物理特性出發(fā),提出新的理論模型,開發(fā)地下洞室三維流變數(shù)值仿真計算程序,針對軟巖地下洞室施工開挖過程中的流變機(jī)理、圍巖變形特性和支護(hù)結(jié)構(gòu)受力狀態(tài)展開進(jìn)一步的數(shù)值研究,旨在為今后工程設(shè)計施工提供合理建議,確保工程的可行性、安全性和經(jīng)濟(jì)性。主要內(nèi)容如下:(1)歸納軟巖流變特性、數(shù)值計算方法和地下洞室存在的流變問題,研究經(jīng)典的巖石流變理論西原模型的含義。結(jié)果表明:西原模型存在兩個問題:其一,不能準(zhǔn)確地描述軟巖單軸壓縮狀態(tài)下的典型蠕變發(fā)展過程,特別是應(yīng)變率隨時間增大的加速蠕變階段;其二,只考慮應(yīng)力和長期強度的關(guān)系,復(fù)雜應(yīng)力狀態(tài)下未考慮屈服函數(shù)對應(yīng)力狀態(tài)的評判作用,進(jìn)而影響施加黏塑性應(yīng)變時間點的判斷。(2)針對西原模型存在的兩個問題,在西原模型的基礎(chǔ)上,引入塑性屈服函數(shù)以及應(yīng)力水平和長期強度的大小關(guān)系兩個開關(guān)函數(shù),建立包含流變時間、應(yīng)力水平和塑性屈服函數(shù)等在內(nèi)的雙開關(guān)西原模型。結(jié)果表明:雙開關(guān)西原模型能夠反映不同巖石或者同種巖石在不同的應(yīng)力水平下的蠕變過程;進(jìn)行復(fù)雜應(yīng)力狀態(tài)條件下的三維本構(gòu)推演,為后續(xù)三維流變有限元程序開發(fā)奠定理論基礎(chǔ)。(3)引用增量變塑性剛度初應(yīng)變法,根據(jù)雙開關(guān)西原模型理論進(jìn)行三維推演,結(jié)合軟巖地下洞室施工開挖流程和支護(hù)原則,開發(fā)地下洞室三維流變有限元程序。結(jié)果表明:增量變塑性剛度初應(yīng)變法能夠取得較快的計算速度和較穩(wěn)定的收斂效果;編制的計算程序?qū)崿F(xiàn)了洞室開挖靜力、支護(hù)和流變效應(yīng)數(shù)值模擬的統(tǒng)一,為評判軟巖地下洞室圍巖穩(wěn)定性和支護(hù)安全性提供計算平臺。(4)基于邱賢德等完成的軟巖單軸壓縮物理試驗,利用編制的地下洞室三維流變有限元程序進(jìn)行軟巖單軸壓縮數(shù)值試驗,開展基于雙開關(guān)西原模型的毛洞流變效應(yīng)研究。結(jié)果表明:物理試驗和數(shù)值試驗曲線擬合優(yōu)度較高,毛洞流變過程中圍巖損傷區(qū)和位移值不斷增大將發(fā)生破壞,該理論能夠更為準(zhǔn)確地模擬物理試驗反映的軟巖流變過程,合理地模擬出軟巖洞室毛洞開挖完成后的流變特點。(5)針對滇中引水工程鳳屯隧洞的地質(zhì)特點,選擇典型的Ⅳ類軟巖洞段進(jìn)行洞室開挖、支護(hù)和160天流變效應(yīng)研究。結(jié)果表明:毛洞開挖、一次支護(hù)條件下,臨空面圍巖變形大、受壓損傷嚴(yán)重、局部錨桿失效;必須施加二次支護(hù),擬定襯砌結(jié)構(gòu)能夠長期抵抗圍巖擠壓作用,有效地限制軟巖變形和塑性損傷區(qū)發(fā)展,改善洞周圍巖應(yīng)力狀態(tài),確保錨桿長期發(fā)揮支護(hù)作用,實現(xiàn)隧洞的長期穩(wěn)定。
[Abstract]:With the rapid development of China's economy and the promotion of urbanization, the construction of water conservancy, energy, transportation, national defense and other infrastructure facilities are more involved in the development of underground space, and the construction of underground engineering is facing more new challenges and new problems. The long-term stability of soft rock underground caverns is often the key to the successful completion of the project. Based on the Fengtun Tunnel, a water diversion project in central Yunnan Province, a new theoretical model is proposed based on the rheological and physical characteristics of soft rock. A numerical simulation program for 3D rheology of underground caverns is developed to further study the rheological mechanism, deformation characteristics of surrounding rock and mechanical state of supporting structures during excavation of underground caverns in soft rock. In order to provide reasonable suggestions for future engineering design and construction, to ensure the feasibility, safety and economy of the project, the main contents are as follows: 1) Induction of rheological characteristics of soft rock, numerical calculation method and rheological problems existing in underground cavern, The meaning of the classical rock rheological model is studied. The results show that the model has two problems: first, it can not accurately describe the typical creep development process of soft rock under uniaxial compression. In particular, the accelerated creep stage in which the strain rate increases with time; secondly, the relationship between stress and long-term strength is considered only, and the effect of yield function on the stress state is not considered in complex stress state. Then influence the judgment of time point of viscoplastic strain. (2) aiming at the two problems existing in Xiyuan model, the plastic yield function and the relationship between stress level and long-term strength are introduced on the basis of Xiyuan model, and two switching functions are introduced. The double Kansai original model, including rheological time, stress level and plastic yield function, is established. The results show that the double Kansai original model can reflect the creep process of different rocks or the same rock at different stress levels. The three-dimensional constitutive model under complex stress state is derived, which lays a theoretical foundation for the subsequent development of three-dimensional rheological finite element program. The incremental variable plastic stiffness initial strain method is used to derive the three-dimensional constitutive equation according to the original model theory of Shuangkaikansai. Combined with the excavation process and supporting principle of soft rock underground cavern, the three-dimensional rheological finite element program is developed. The results show that the incremental variable plastic stiffness initial strain method can obtain faster calculation speed and more stable convergence effect. The calculation program has realized the unification of static force, support and rheological effect numerical simulation of cavern excavation. In order to evaluate the surrounding rock stability and support safety of soft rock underground caverns, this paper provides a calculation platform. 4. Based on Qiu Xiande et al., the physical test of soft rock uniaxial compression is carried out. The three-dimensional rheological finite element program of underground cavern is used to carry out uniaxial compression numerical test of soft rock, and the rheological effect of Mao cave is studied based on the original model of double kaikansi. The results show that the fitting degree of physical test and numerical test curve is high. The damage zone and displacement value of surrounding rock will be destroyed during the rheological process of cavern, and the theory can more accurately simulate the rheological process of soft rock reflected by physical test. According to the geological characteristics of Fengtun tunnel in central Yunnan water diversion project, the typical type 鈪，

本文編號：1635071