發(fā)布時間：2018-03-06 00:22

  本文選題：富水弱膠結砂層　切入點：雙側壁導坑法　出處：《蘭州交通大學》2014年碩士論文　論文類型：學位論文

【摘要】：需要大力發(fā)展交通工程的中國西北地區(qū)廣泛分布著富水弱膠結砂層，在這種典型軟巖地層中修建大斷面隧道工程的難度比較大、安全風險高，嚴重制約著我國西北地區(qū)交通工程的發(fā)展。如何在此類軟弱圍巖地質條件下，安全、高效的修建高質量隧道，是當前隧道工程界面臨的重要課題之一。 本文依托在建的蘭渝鐵路桃樹坪隧道工程，研究探討了富水弱膠結粉細砂層隧道雙側壁導坑施工工法及其輔助施工措施等關鍵技術；對隧道施工過程中的相關應力項目進行了監(jiān)測和分析；采用有限元軟件對隧道施工過程進行了模擬，研究分析了圍巖變形規(guī)律、支護結構應力分布特征及其變化規(guī)律，并結合監(jiān)測結果綜合評價了現行施工方法、支護參數的可行性和支護結構的安全性。綜合以上內容的研究分析，得出了以下主要研究成果： （1）在此類特殊富水軟巖地層中修建隧道等地下工程時，施工技術的關鍵在于以降水為前提，超前注漿加固為保障，大斷面劃分成小斷面（雙側壁工法），快挖、快支、快封閉為組織原則，這樣才能有效的控制圍巖的變形，確保隧道施工安全、高效的推進。 （2）通過對圍巖壓力、接觸壓力、二襯鋼筋內力的監(jiān)測和分析，可以看出各監(jiān)測點的圍巖壓力、接觸壓力以及二襯鋼筋內力等均呈現出了不規(guī)律波動變化的特性，受各部開挖、臨時支撐的拆除影響較大，出現長時間波動情況，，在監(jiān)測3到5個月后都呈現出了收斂趨勢，基本穩(wěn)定，數值均在允許范圍之內，支護結構處于安全狀態(tài)。 （3）通過對隧道施工過程進行數值模擬分析，可以看出在此類地層中修建隧道時，圍巖易被擾動，擾動范圍大，變形速度快，變形時間長，隧道貫通后豎直和水平位移最大值分別為23.6mm和11.2mm；鑒于雙側壁導坑法施工的不對稱性，支護結構的受力表現出了不對稱性，隧道貫通后初期支護結構的第1和第3主應力最大值分別達到了1.4MPa和-21.7MPa，支護結構受力處于正常狀態(tài)。 （4）拆除臨時支撐是雙側壁導坑法施工比較關鍵的一道工序，在拆除臨時支撐時，對圍巖的位移及支護結構的受力都會產生重要的影響，圍巖位移和支護結構的應力都會發(fā)生突變，突變值較大；研究斷面的支護結構應力最大突變值達到了7.4MPa，占到了最大值的37.7%。因此要盡量分段、小范圍、小震動拆除，避免對圍巖造成較大擾動，并且要加強該段圍巖量測頻率，發(fā)現變形過大時，盡早采取措施，加強支護，控制該部位受力狀態(tài)的惡化及變形的擴大。
[Abstract]:In northwest China, where traffic engineering needs to be vigorously developed, there are widely water-rich and weak-cemented sand beds. It is difficult to build large section tunnels in this typical soft rock formation, and the safety risks are high. The development of traffic engineering in northwest China is seriously restricted. How to build high quality tunnel safely and efficiently under the geological condition of soft surrounding rock is one of the important problems facing the tunnel engineering field at present. Based on the Taoshuping tunnel project of the Lanzhou-Chongqing railway, this paper discusses the construction method of double-sidewall diversion pit and its auxiliary construction measures for the tunnel with rich water and weak cemented fine sand layer. The related stress items in tunnel construction are monitored and analyzed, the tunnel construction process is simulated by finite element software, the surrounding rock deformation law, the stress distribution characteristics of supporting structure and its variation law are studied and analyzed. Combined with the monitoring results, comprehensive evaluation of the current construction methods, the feasibility of supporting parameters and the safety of the support structure. Based on the above research and analysis, the following main research results are obtained:. 1) in the construction of tunnels and other underground projects in this kind of special water-rich soft rock strata, the key point of construction technology is to take precipitation as the premise and advance grouting reinforcement as the guarantee, and the large sections are divided into small sections (double side wall construction method, quick excavation, quick branch, etc.). Fast closure is the principle of organization so that the deformation of surrounding rock can be controlled effectively and the tunnel construction is safe and efficient. 2) through the monitoring and analysis of surrounding rock pressure, contact pressure and internal force of second lining steel bar, it can be seen that the surrounding rock pressure, contact pressure and internal force of the second lining steel bar all show irregular fluctuation characteristics, and are excavated by each part. The removal of temporary braces has a great influence on the removal of temporary braces and has a long period of fluctuation. After monitoring for 3 to 5 months, the temporary bracing shows a convergent trend, which is basically stable, and the values are all within the allowable range, and the supporting structure is in a safe state. 3) through the numerical simulation analysis of tunnel construction process, it can be seen that the surrounding rock is easily disturbed, the disturbance range is large, the deformation speed is fast, and the deformation time is long when the tunnel is built in this kind of stratum. The maximum values of vertical and horizontal displacement after tunnel opening are 23.6mm and 11.2mm respectively. The maximum of the first and third principal stresses of the primary support structure of the tunnel is up to 1.4 MPA and -21.7 MPA, respectively, and the force of the supporting structure is in the normal state. The removal of temporary bracing is a key procedure in the construction of double-side wall diversion pit method. When the temporary support is removed, it will have an important impact on the displacement of surrounding rock and the force on the supporting structure. The displacement of surrounding rock and the stress of supporting structure will both change, and the catastrophe value will be larger. The maximum abrupt value of stress of supporting structure in the research section has reached 7.4 MPA, accounting for 37.7% of the maximum value. In order to avoid the disturbance to the surrounding rock, and to strengthen the measuring frequency of the surrounding rock, when the deformation is too large, measures should be taken as soon as possible to strengthen the support, to control the deterioration of the stress state and the expansion of the deformation.
【學位授予單位】：蘭州交通大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：U455.4

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