鄰近基坑開挖對地鐵隧道變形的影響研究
發(fā)布時間：2018-10-23 12:35
【摘要】：地鐵為城市交通命脈,緊鄰地鐵的基坑設(shè)計中必須考慮到對地鐵區(qū)間隧道的影響。目前已有較大量研究成果闡述了基坑開挖卸荷的環(huán)境效應。但在周邊存在地鐵隧道的情況下,對開挖卸荷時基坑圍護墻體變形的影響、受擾動土體變形規(guī)律及隧道變形響應等方面的研究相對較少,亟待解決的問題很多。本文分析和指出了鄰近基坑開挖時隧道變形解析法存在的缺陷和不足,進而采用FLAC3D軟件模擬武漢地鐵4號線附近某基坑開挖過程,得到了在基坑開挖與隧道相互影響條件下基坑圍護結(jié)構(gòu)、坑底土體及隧道結(jié)構(gòu)的變形規(guī)律。分別討論了坑頂堆載、土體性質(zhì)、圍護結(jié)構(gòu)布置、隧道與基坑水平及豎直距離對鄰近隧道變形的影響。總結(jié)和提出了隧道變形控制標準和合理的加固措施及建議。主要的研究成果如下:(1)對附加應力法和附加位移法兩種解析方法進行了探討。著重對附加應力、附加位移及地基梁變形進行了求解,指出兩種解析法存在的缺陷和不足:附加應力法計算復雜,無法考慮施工過程的影響,且對設(shè)有支撐時的基坑側(cè)向卸荷應力的假設(shè)不合理;附加位移法為一種半理論半經(jīng)驗公式方法,受人為假設(shè)等主觀因素的影響較大,且需要用前期監(jiān)測數(shù)據(jù)來驗證結(jié)果可靠性。(2)用FLAC3D軟件模擬武漢地鐵4號線附近某基坑開挖過程。基坑圍護結(jié)構(gòu)在坑底處位移最大,且圍護墻變形受隧道的影響較大,在近隧道側(cè)墻頂位移較大,而坑底處位移較小;在隧道離基坑長邊中點較近時地鐵隧道變形較大,離基坑遠處較小。與三維立體模型相比,平面模型隧道最大豎向位移計算值小10%,最大水平位移計算值大10%。在坑頂堆載較大時會增大隧道的水平變形;隧道所處土層材料性質(zhì)在適當范圍內(nèi)變化時,對隧道豎向變形影響較小,而對其水平變形影響較大。(3)總結(jié)和提出的隧道變形控制標準為:豎向變形允許值不大于10mm,水平變形允許值不大于5mm,預警值為允許值的80%�；臃侄伍_挖和施工過程中及時施做底板,可明顯減小地鐵隧道變形;而在坑底底板上快速堆載及基坑被動區(qū)土體加固的控制效果較為顯著。而以往采用增加基坑內(nèi)支撐或提高隧道截面剛度時,其變形控制效果較差。
[Abstract]:Subway is the lifeblood of city traffic. The influence of subway tunnel must be considered in the design of foundation pit next to subway. At present, a large number of research results have expounded the environmental effects of excavation unloading. However, in the case of the surrounding subway tunnel, the deformation of the retaining wall of the foundation pit is affected by the disturbance soil deformation law and the tunnel deformation response, so there are a lot of problems to be solved. This paper analyzes and points out the defects and shortcomings of the analytical method of tunnel deformation during excavation of adjacent foundation pit, and then uses FLAC3D software to simulate the excavation process of a foundation pit near Wuhan Metro Line 4. The deformation law of foundation pit retaining structure, pit bottom soil and tunnel structure is obtained under the interaction of excavation and tunnel. The effects of pile load, soil properties, the arrangement of enclosure structure, the horizontal and vertical distance between tunnel and foundation pit on the deformation of adjacent tunnels are discussed respectively. The control standard of tunnel deformation and reasonable reinforcement measures and suggestions are summarized and put forward. The main results are as follows: (1) two analytical methods, the additional stress method and the additional displacement method, are discussed. The additional stress, the additional displacement and the deformation of the foundation beam are solved emphatically. The defects and shortcomings of the two analytical methods are pointed out: the calculation of the additional stress method is complicated, and the influence of the construction process cannot be considered. Moreover, the assumption of lateral unloading stress of foundation pit with bracing is unreasonable, and the additional displacement method is a semi-theoretical and semi-empirical formula method, which is greatly influenced by subjective factors such as artificial hypothesis, etc. And it is necessary to verify the reliability of the results with the pre-monitoring data. (2) the excavation process of a foundation pit near Wuhan Metro Line 4 is simulated by FLAC3D software. The displacement of foundation pit enclosure structure is the largest at the bottom of the pit, and the deformation of the retaining wall is greatly affected by the tunnel, the displacement near the side wall of the tunnel is larger, but the displacement at the bottom of the pit is smaller, and when the tunnel is near the midpoint of the long side of the foundation pit, the deformation of the subway tunnel is larger. The distance from the foundation pit is smaller. Compared with the three-dimensional model, the maximum vertical displacement of the plane model tunnel is 10% smaller than that of the three-dimensional model, and the maximum horizontal displacement value is 10%. The horizontal deformation of the tunnel will be increased when the top of the pit is larger, and the vertical deformation of the tunnel will be less affected by the change of the properties of the soil layer in the tunnel within an appropriate range. (3) the allowable value of vertical deformation is not greater than 10mm, the allowable value of horizontal deformation is not greater than 5mm, and the warning value is 80% of the allowable value. In the process of excavation and construction of foundation pit, the deformation of subway tunnel can be obviously reduced by using the floor plate in time, while the control effect of quick surcharge on the bottom slab and reinforcement of soil in passive zone of foundation pit is more remarkable. In the past, the deformation control effect was poor when increasing the support inside the foundation pit or increasing the cross-section stiffness of the tunnel.
【學位授予單位】：武漢理工大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：U456;TU753
本文編號：2289257
[Abstract]:Subway is the lifeblood of city traffic. The influence of subway tunnel must be considered in the design of foundation pit next to subway. At present, a large number of research results have expounded the environmental effects of excavation unloading. However, in the case of the surrounding subway tunnel, the deformation of the retaining wall of the foundation pit is affected by the disturbance soil deformation law and the tunnel deformation response, so there are a lot of problems to be solved. This paper analyzes and points out the defects and shortcomings of the analytical method of tunnel deformation during excavation of adjacent foundation pit, and then uses FLAC3D software to simulate the excavation process of a foundation pit near Wuhan Metro Line 4. The deformation law of foundation pit retaining structure, pit bottom soil and tunnel structure is obtained under the interaction of excavation and tunnel. The effects of pile load, soil properties, the arrangement of enclosure structure, the horizontal and vertical distance between tunnel and foundation pit on the deformation of adjacent tunnels are discussed respectively. The control standard of tunnel deformation and reasonable reinforcement measures and suggestions are summarized and put forward. The main results are as follows: (1) two analytical methods, the additional stress method and the additional displacement method, are discussed. The additional stress, the additional displacement and the deformation of the foundation beam are solved emphatically. The defects and shortcomings of the two analytical methods are pointed out: the calculation of the additional stress method is complicated, and the influence of the construction process cannot be considered. Moreover, the assumption of lateral unloading stress of foundation pit with bracing is unreasonable, and the additional displacement method is a semi-theoretical and semi-empirical formula method, which is greatly influenced by subjective factors such as artificial hypothesis, etc. And it is necessary to verify the reliability of the results with the pre-monitoring data. (2) the excavation process of a foundation pit near Wuhan Metro Line 4 is simulated by FLAC3D software. The displacement of foundation pit enclosure structure is the largest at the bottom of the pit, and the deformation of the retaining wall is greatly affected by the tunnel, the displacement near the side wall of the tunnel is larger, but the displacement at the bottom of the pit is smaller, and when the tunnel is near the midpoint of the long side of the foundation pit, the deformation of the subway tunnel is larger. The distance from the foundation pit is smaller. Compared with the three-dimensional model, the maximum vertical displacement of the plane model tunnel is 10% smaller than that of the three-dimensional model, and the maximum horizontal displacement value is 10%. The horizontal deformation of the tunnel will be increased when the top of the pit is larger, and the vertical deformation of the tunnel will be less affected by the change of the properties of the soil layer in the tunnel within an appropriate range. (3) the allowable value of vertical deformation is not greater than 10mm, the allowable value of horizontal deformation is not greater than 5mm, and the warning value is 80% of the allowable value. In the process of excavation and construction of foundation pit, the deformation of subway tunnel can be obviously reduced by using the floor plate in time, while the control effect of quick surcharge on the bottom slab and reinforcement of soil in passive zone of foundation pit is more remarkable. In the past, the deformation control effect was poor when increasing the support inside the foundation pit or increasing the cross-section stiffness of the tunnel.
【學位授予單位】：武漢理工大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：U456;TU753
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