隧道出口明挖段深基坑施工過程中的變形及穩(wěn)定性研究
發(fā)布時間：2018-09-18 20:34
【摘要】：就基坑工程在開挖過程中的內力和變形規(guī)律,巖土工作者已做了大量的研究,但對于狹長型基坑在開挖過程中基坑受力、變形機理的實測和分析卻較少。隨著我國大規(guī)模的進行城市軌道建設,這類型基坑會大量遇到,對此類基坑在開挖過程中的受力和變形機理進行研究探討,可以為以后類似工程的設計和施工積累經驗。在閱讀大量國內外相關文獻,總結相關研究成果的基礎上。本文以哈爾濱到牡丹江客運專線(哈牡客專)愛民隧道出口明挖段狹長型深基坑在開挖過程中的現場監(jiān)測為依托,結合理論分析及三維數值模擬分析,指導現場施工、反饋設計的同時對本地區(qū)狹長基坑在開挖過程中圍護結構的受力、變形以及開挖對周邊環(huán)境的影響進行了初步探討。最后,通過三維數值模擬分析的方法對圍護結構參數進行了多方位優(yōu)化,為工程后續(xù)施工以及本地區(qū)類似基坑工程設計、施工提供參考。本文主要內容及相關結論如下:(1)通過現場監(jiān)測可知,基坑施工全過程中,各監(jiān)測項目的量均未達到報警值,圍護結構正常工作�；訌拈_挖暴露到底板施做完畢全過程中,樁身水平位移最大值達到13.72mm,位于撐間樁上距樁頂往下8.0m左右處,位置隨著最大值增加不斷下移,剛開挖到底時最大值在距樁頂7.0m左右處;樁身彎矩最大值也發(fā)生在撐間樁上,最大值達到了464.0kN.m,與樁身正截面抗彎承載力1410kN.m相距甚遠,究其原因,是由于現場實測得到的樁頂和樁底均發(fā)生了一定量的水平位移,這樣勢必會對圍護樁的內力產生一定的釋放作用;現場實測得到的橫撐和冠梁位移及受力均處于較小狀態(tài)。(2)對比現場實測、三維有限元分析及規(guī)范法得到的樁身水平位移,規(guī)范法得到的值最大,最大值達到了16.78mm,最大值發(fā)生位置與三維有限元分析得到的最大值位置一致,發(fā)生在距樁頂7.5m左右處,現場實測得到的最大值位置略微向下,位于距樁頂8.0m左右處;對樁身彎矩而言,三維有限元分析下的最大值為883.1kN.m,規(guī)范法計算的最大值為966.5kN.m,現場實測結果卻小很多,最大值只有464.0kN.m,由內里釋放引起;冠梁的內力及變形三種方法得到的結果大小與趨勢均較接近。(3)為了綜合評價基坑的穩(wěn)定性,通過經驗公式和三維有限元分析對地表沉降和坑底隆起進行估算。經驗公式得到的地表沉降最大值為10.7mm,發(fā)生在距樁頂6.9m處;三維有限元分析得到的地表最大沉降為11.2mm,距樁頂6.5m處;經驗公式得到的坑底隆起最大值為10.2mm,三維有限元分析得到的坑底隆起最大值為12.1mm,發(fā)生在距離圍護結構約1.0m處。(4)各優(yōu)化方案中,改變錨固段長度對圍護結構的受力及變形影響均最小;改變樁徑對圍護樁及橫撐的影響最為劇烈,當樁徑從1.0m減小到0.7m時,水平位移最大值達到28.0mm,與30mm的報警值已非常接近,樁身彎矩已達到了樁身正截面彎矩承載力的85.4%,此時橫撐彎矩相較原模型增大了139%,已經超過了橫撐正截面抗彎承載力815kN.m;冠梁彎矩卻是對樁間距的改變最為敏感,但是在整個優(yōu)化過程中,冠梁彎矩均處于較小狀態(tài)。最后提出一種適用于按照現場施工工序施工的圍護結構設計方案,此方案在保證施工安全的前提下,經濟合理。
[Abstract]:Geotechnical workers have done a lot of research on the internal force and deformation law of foundation pit engineering in the excavation process, but there are few measurement and Analysis on the deformation mechanism of the narrow and long foundation pit in the excavation process. On the basis of reading a large number of relevant literatures at home and abroad and summarizing the relevant research results, this paper takes Harbin-Mudanjiang Passenger Dedicated Line (Harbin-Mudanjiang Passenger Dedicated Line) Aimin tunnel exit open-cut section of the narrow deep foundation pit excavation in the excavation. Based on the field monitoring in the process of excavation, combined with theoretical analysis and three-dimensional numerical simulation analysis, the field construction is guided and the feedback design is carried out. At the same time, the force, deformation of the retaining structure and the influence of excavation on the surrounding environment in the process of excavation are preliminarily discussed. The main contents and related conclusions are as follows: (1) Through on-site monitoring, it is known that during the whole process of foundation pit construction, the amount of monitoring items has not reached the alarm value, and the retaining structure works normally. The maximum horizontal displacement of pile body reaches 13.72 m m in the whole process of exposed floor construction, which is located at the position of 8.0 m downward from the top of pile between bracing piles. With the increase of the maximum position, the maximum value is about 7.0 m from the top of pile when excavated. The maximum bending moment of pile body also occurs on the pile between bracing piles, the maximum value is 464.0 kN.m, and the pile top. The bending bearing capacity of the normal section is far from 1410kN.m. The reason is that a certain amount of horizontal displacement occurs at the top and bottom of the pile, which is bound to release the internal force of the retaining pile. The maximum horizontal displacement obtained by the code method is 16.78 mm. The location of the maximum displacement is consistent with that obtained by the three-dimensional finite element analysis. It occurs about 7.5 meters from the pile top. The maximum displacement measured by the field is slightly downward and located 8.0 meters to the left of the pile top. For the pile bending moment, the maximum value of the three-dimensional finite element analysis is 883.1 kN.m, the maximum value of the code method is 966.5 kN.m, but the field measurement results are much smaller, the maximum value is only 464.0 kN.m, which is caused by internal release; the internal force and deformation of the crown and beam are close to the trend of the three methods. (3) In order to evaluate the foundation comprehensively. The stability of the pit is estimated by empirical formula and three-dimensional finite element analysis. The maximum ground settlement is 10.7 mm from the top of the pile and 6.9 m from the top of the pile. 10.2 mm, the maximum value of pit bottom uplift obtained by three-dimensional finite element analysis is 12.1 mm, occurring about 1.0 m away from the retaining structure. (4) In all optimization schemes, changing the length of anchorage section has the least influence on the stress and deformation of the retaining structure; changing the diameter of the pile has the most severe influence on the retaining pile and the transverse brace, when the diameter of the pile decreases from 1.0 m to 0.7 m, the horizontal displacement is the smallest. The maximum value is 28.0m m, which is very close to the warning value of 30m M. The bending moment of pile body has reached 85.4% of the bearing capacity of normal section moment of pile body. At this time, the bending moment of transverse bracing has increased by 139% compared with the original model, and has exceeded the bending capacity of normal section of transverse bracing by 815kN.m. Finally, a design scheme of envelope structure suitable for construction according to site construction procedure is put forward, which is economical and reasonable on the premise of ensuring construction safety.
【學位授予單位】：蘭州交通大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：U455
本文編號：2249034
[Abstract]:Geotechnical workers have done a lot of research on the internal force and deformation law of foundation pit engineering in the excavation process, but there are few measurement and Analysis on the deformation mechanism of the narrow and long foundation pit in the excavation process. On the basis of reading a large number of relevant literatures at home and abroad and summarizing the relevant research results, this paper takes Harbin-Mudanjiang Passenger Dedicated Line (Harbin-Mudanjiang Passenger Dedicated Line) Aimin tunnel exit open-cut section of the narrow deep foundation pit excavation in the excavation. Based on the field monitoring in the process of excavation, combined with theoretical analysis and three-dimensional numerical simulation analysis, the field construction is guided and the feedback design is carried out. At the same time, the force, deformation of the retaining structure and the influence of excavation on the surrounding environment in the process of excavation are preliminarily discussed. The main contents and related conclusions are as follows: (1) Through on-site monitoring, it is known that during the whole process of foundation pit construction, the amount of monitoring items has not reached the alarm value, and the retaining structure works normally. The maximum horizontal displacement of pile body reaches 13.72 m m in the whole process of exposed floor construction, which is located at the position of 8.0 m downward from the top of pile between bracing piles. With the increase of the maximum position, the maximum value is about 7.0 m from the top of pile when excavated. The maximum bending moment of pile body also occurs on the pile between bracing piles, the maximum value is 464.0 kN.m, and the pile top. The bending bearing capacity of the normal section is far from 1410kN.m. The reason is that a certain amount of horizontal displacement occurs at the top and bottom of the pile, which is bound to release the internal force of the retaining pile. The maximum horizontal displacement obtained by the code method is 16.78 mm. The location of the maximum displacement is consistent with that obtained by the three-dimensional finite element analysis. It occurs about 7.5 meters from the pile top. The maximum displacement measured by the field is slightly downward and located 8.0 meters to the left of the pile top. For the pile bending moment, the maximum value of the three-dimensional finite element analysis is 883.1 kN.m, the maximum value of the code method is 966.5 kN.m, but the field measurement results are much smaller, the maximum value is only 464.0 kN.m, which is caused by internal release; the internal force and deformation of the crown and beam are close to the trend of the three methods. (3) In order to evaluate the foundation comprehensively. The stability of the pit is estimated by empirical formula and three-dimensional finite element analysis. The maximum ground settlement is 10.7 mm from the top of the pile and 6.9 m from the top of the pile. 10.2 mm, the maximum value of pit bottom uplift obtained by three-dimensional finite element analysis is 12.1 mm, occurring about 1.0 m away from the retaining structure. (4) In all optimization schemes, changing the length of anchorage section has the least influence on the stress and deformation of the retaining structure; changing the diameter of the pile has the most severe influence on the retaining pile and the transverse brace, when the diameter of the pile decreases from 1.0 m to 0.7 m, the horizontal displacement is the smallest. The maximum value is 28.0m m, which is very close to the warning value of 30m M. The bending moment of pile body has reached 85.4% of the bearing capacity of normal section moment of pile body. At this time, the bending moment of transverse bracing has increased by 139% compared with the original model, and has exceeded the bending capacity of normal section of transverse bracing by 815kN.m. Finally, a design scheme of envelope structure suitable for construction according to site construction procedure is put forward, which is economical and reasonable on the premise of ensuring construction safety.
【學位授予單位】：蘭州交通大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：U455
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