【作者】 陈文；

【导师】 李欣；

【作者基本信息】 吉林大学 ， 岩土工程， 2019， 硕士

【摘要】 中国经济自20世纪末以来已进入快速发展的阶段,城市建设速度也在加快,城市地铁及高层建筑等深基坑工程不断涌现。为减少深基坑工程的隐患,有必要对其开挖及支护进行研究。不同支护结构适用范围有所不同。从20世纪80年代开始,桩锚支护结构开始得到广泛应用。与其他支护结构相比,桩锚支护不仅可以有效利用施工空间,而且还可以有效地控制地层变形,因而这种基坑支护结构形式目前在我国也最常用。桩锚支护形式涉及到的基础学科较多,是一项涉及面广、难度较高的综合性课题。本论文归纳前人研究成果,介绍了基坑变形的原理及类型。结合长春市北湖地区某深基坑工程,介绍了监测方案和基坑支护方案,处理实际监测数据,分析基坑实际变形情况。同时运用FLAC3D6.0软件模拟基坑开挖支护步骤,得出地表沉降、桩体深层水平位移及锚杆轴力模拟结果,并将模拟结果与现场实测数据进行对比分析,得出在开挖过程中基坑土体及桩锚支护结构的变形分布规律。研究结论如下:1.基坑开挖时,支护桩内外两侧存在土压力差,桩体产生水平位移,水平位移值随开挖的进行逐渐增大,支护桩的最大水平位移是在桩身中上部。在设锚索的位置,桩身各点的水平位移值出现了“M”型变化的情况,位移值先变大,后减小,再变大,说明设置锚索可以有效控制位移值。2、土体的水平位移值和沉降量逐渐增大。每次开挖土体的水平位移先增大后减小,每设一道锚杆土体的水平位移值增量都会得到控制。地表沉降值随着与坡顶的距离越来越远其沉降量逐渐减小。基坑底部有隆起,从基坑底部中心沿四周由大变小。3、锚索轴力为拉力,由上至下轴力增大,每一排锚索的轴力都是中间大,两端小。从靠近自由段的部分向锚固段方向由大变小。4.监测结果显示西侧土体水平位移值和沉降量大于东侧,究其原因可能是西侧新建板房以及堆载施工材料导致压力过大,再加上施工速度过快导致的,西侧临近开挖临空面的道路出现一道裂缝可以佐证。5.实测值和模拟值相比实测值偏大,说明实际模拟时考虑因素略有欠缺,参数准确性及外界因素均可以导致模拟结果出现误差。二者变化趋势大致吻合,表明在一定程度上用FLAC3D模拟基坑的开挖变形是可行的。比较监测结果和模拟结果,基坑变形量均控制在规范允许值范围内,说明桩锚支护设计合理,模型的建立和参数选取大致无误,从而为本地区类似基坑优化支护设计提供参考。更多还原

【Abstract】 China’s economy has entered a stage of rapid development since the end of 20 th century,the speed of urban construction is also accelerating,urban subways and high-rise buildings and other deep foundation pit projects continue to emerge.In order to reduce the hidden trouble of Deep foundation pit engineering,it is necessary to study its excavation and support.The scope of application of different support structures is different.Since the the1980 s,pile anchor support structure has been widely used.Compared with other supporting structures,pile anchor support can not only make effective use of construction space,but also effectively control formation deformation,so this kind of foundation pit support structure form is also most commonly used in China.The form of pile anchor support involves more basic subjects,which is a comprehensive subject with wide scope and high difficulty.This paper summarizes the previous research results and introduces the principle and type of foundation pit deformation.Combining with a deep foundation pit project in Changchun Beihu area,this paper introduces the monitoring Scheme and foundation pit Support scheme,handles the actual monitoring data,and analyzes the actual deformation of the foundation pit.At the same time,using FLAC3D6.0software to simulate the excavation support steps of foundation Pit,the simulation results of surface subsidence,deep horizontal displacement of pile body and axial force of anchor rod are obtained,and the simulation results are compared with the measured data in the field,and the deformation distribution law of foundation pit soil and pile anchor support structure in excavation process is obtained.The conclusions of the study are as follows:1.When the foundation pit is excavated,there is poor soil pressure on both sides of the support pile,the pile body produces horizontal displacement,the horizontaldisplacement value increases gradually with the excavation,and the maximum horizontal displacement of the support pile is in the upper part of the pile body.In the position of anchor cable,the horizontal displacement value of each point of pile body shows the change of "M" type,the displacement value becomes larger first,then decreases and then becomes larger,which indicates that the displacement value can be effectively controlled by setting anchor cable.2.The horizontal displacement value and sedimentation of soil increase gradually.The horizontal displacement of the soil in each excavation increases first and then decreases,and the increase of the horizontal displacement value of each anchor soil will be controlled.The settlement value decreases gradually with the distance from the top of the slope.The bottom of the foundation Pit has a bulge,from the center of the bottom of the foundation pit along the perimeter by large smaller.3.Anchor cable axial force for tension,from the upper to lower axial force increased,each row of Anchor cable axial force is the middle large,the two ends are small.From the part near the free segment to the Anchorage section direction from large to small.4.The monitoring results show that the horizontal displacement value and settlement of the western soil are greater than the east side,which may be due to the new board room on the west side and the load construction materials caused by excessive pressure,coupled with the construction speed is too fast,the west side near the excavation of the empty surface of the road there is a crack can be supported.5.The measured value and the simulated value are larger than the measured value,which indicates that the factors considered in the actual simulation are slightly deficient,and the accuracy of the parameters and external factors can lead to errors in the simulation results.The change trend of the two is generally consistent,which shows that it is feasible to simulate the excavation deformation of foundation pit with FLAC3 D to a certain extent.Comparing the monitoring results and simulation results,the deformation of foundation pit is controlled within the range of standard allowable value,which shows that the design of pile anchor support is reasonable,the establishment of the modeland the selection of parameters are roughly correct,so as to provide reference for the optimal support design of foundation pit similar in this area.更多还原