【摘要】：隧道作為一種十分重要交通構(gòu)筑物形式,在高速公路和高速鐵路的建設(shè)中不可避免,為了節(jié)約用地、保護(hù)既有建筑物或環(huán)境將會更多的采用隧道下穿的方式。隧道下穿既有高速公路成為近年來的一種常見形式,而隧道的頂部覆蓋層較薄,圍巖為路基填筑材料,穩(wěn)定性差,極易產(chǎn)生較大的變形,甚至失穩(wěn),嚴(yán)重影響隧道施工與高速公路運(yùn)營安全。因此,下穿隧道施工對高速公路路基變形的影響研究具有十分重要的意義。論文以貴州省某下穿既有高速公路的鐵路隧道建設(shè)為研究背景,通過數(shù)值模擬、現(xiàn)場監(jiān)測、理論分析,研究下穿隧道施工對高速公路路基的變形影響規(guī)律。主要研究的工作如下:(1)采用FLAC3D數(shù)值模擬方法對現(xiàn)場施工過程進(jìn)行模擬,分析隧道開挖過程與路基變形的關(guān)系,得出了路基變形規(guī)律:(1)掘進(jìn)深度越大對高速公路路基沉降變形的影響范圍越大,縱向的影響深度普遍超過開挖面的掘進(jìn)深度,橫向影響范圍隨隧道掘進(jìn)深度增加而逐漸增大,最大影響位置為隧道中軸線,監(jiān)測斷面影響最大的為斷面S3,其擴(kuò)散角為49°。(2)采用CRD法施工可以有效控制路基沉降,公路路基最大累計沉降為36.6mm,小于規(guī)范要求的40mm。(3)路基某一斷面的變形速率隨其與隧道的掌子面距離的增大而減小,在掌子面到達(dá)該斷面時沉降速率快速增大,遠(yuǎn)離該斷面時沉降速率快速趨于穩(wěn)定。(2)采用現(xiàn)場監(jiān)控對隧道下穿段路基變形的進(jìn)行分析,得出下穿隧道施工引起的路基沉降的變化規(guī)律以及高速公路路基側(cè)向滑移的變化規(guī)律:(1)CRD法施工對于上方高速公路路基的影響較小,沉降最大值不超過35mm,達(dá)到設(shè)計標(biāo)準(zhǔn)40mm。(2)高速公路路面沉降的變形分別經(jīng)歷超前隆起階段或微小沉降階段、沉降急劇變形階段、沉降緩慢變形階段、沉降穩(wěn)定階段。(3)數(shù)值模擬結(jié)果與現(xiàn)場監(jiān)控結(jié)果差別較小,驗證了數(shù)值模擬結(jié)果的可靠性。(3)基于線性M-C屈服準(zhǔn)則及極限分析上限法,建立掌子面失穩(wěn)導(dǎo)致高速公路路基失穩(wěn)的破壞模式,推導(dǎo)出下穿隧道臨界埋深的上限表達(dá)式,并運(yùn)用非線性規(guī)劃程序優(yōu)化計算獲得臨界最優(yōu)解,分析各種因素對臨界埋深的影響規(guī)律及影響程度。
[Abstract]:As a very important form of traffic structure, tunnel is inevitable in the construction of highway and high-speed railway. In order to save land, to protect existing buildings or environment will be more adopted under the tunnel way. Tunnel underpass through existing highway has become a common form in recent years, but the top of the tunnel overburden is thin, surrounding rock is subgrade filling material, the stability is poor, it is easy to produce large deformation, even instability. The safety of tunnel construction and highway operation is seriously affected. Therefore, it is of great significance to study the influence of underpass tunnel construction on highway roadbed deformation. Based on the research background of the railway tunnel construction of an existing expressway in Guizhou Province, this paper studies the influence of the underpass tunnel construction on the subgrade deformation of the expressway through numerical simulation, field monitoring and theoretical analysis. The main research works are as follows: (1) FLAC3D numerical simulation method is used to simulate the construction process, and the relationship between tunnel excavation process and roadbed deformation is analyzed. The law of roadbed deformation is obtained as follows: (1) the greater the excavation depth, the greater the influence range on the settlement and deformation of expressway subgrade, and the longitudinal influence depth is generally higher than the excavation depth of excavated surface. The transverse influence range increases gradually with the increase of tunneling depth. The maximum influence position is the central axis of the tunnel, the section S3 has the greatest influence on the monitoring section, and the diffusion angle is 49 擄. (2) subgrade settlement can be effectively controlled by using CRD method. The maximum cumulative settlement of highway subgrade is 36.6 mm, which is less than 40mmm. (3) the deformation rate of a section of the roadbed decreases with the increase of the distance between the roadbed and the face of the tunnel, and the settlement rate increases rapidly when the surface of the roadbed reaches the section. The settlement rate tends to be stable rapidly when away from the section. (2) the deformation of the subgrade in the underpass section of the tunnel is analyzed by field monitoring. The variation law of subgrade settlement caused by underpass tunnel construction and lateral slip rule of expressway roadbed are obtained. (1) the influence of CRD construction on the roadbed of the upper expressway is small, and the maximum settlement is not more than 35mm. (2) the settlement of expressway pavement has experienced the stage of advance uplift or small settlement, the stage of rapid settlement, the stage of slow settlement, the second is that the settlement of freeway has reached the design standard of 40mmm. (2) (3) the difference between the numerical simulation results and the field monitoring results is small, which verifies the reliability of the numerical simulation results. (3) based on the linear M-C yield criterion and the upper limit method of limit analysis, The failure mode of roadbed instability caused by metacarpal instability is established, the upper limit expression of critical buried depth of underpass tunnel is derived, and the critical optimal solution is obtained by optimizing calculation with nonlinear programming program. The influence of various factors on critical burial depth is analyzed.
【學(xué)位授予單位】：湖南科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：U416.1

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