【作者】 卫雪；

【导师】 马克生；

【作者基本信息】 太原理工大学 ， 岩土工程， 2012， 硕士

【摘要】 为了城市的可持续发展,人们逐渐将开发的触手伸向了城市更高的高空以及更深的地下,在城市建筑密集区进行了大量的高层、超高层建筑和大规模的地下市政建设,这使得深基坑工程呈现出深、大、密的发展特征,并促进深基坑工程新的支护工艺的产生。桩锚支护技术诞生于1958年,并于上世纪80年代初在我国的高层建筑深基坑工程中开始得到应用,由于其广泛的地层适用条件、优于其他支护形式的技术优势以及其巨大的经济效益,被广泛应用于我国深基坑工程建设。预留土堤,也被称作预留反压土、预留土台,是大面积基坑开挖采用中心岛法施工时所采取的一种施工手段,这是一种新兴的施工手段。当前采用预留土堤对支护结构进行临时支撑的基坑工程中,仅仅是把预留土堤看做是一种控制基坑变形和对周围环境效应的一种施工手段,而没有将其作为设计因素在支护结构设计时就进行考虑。但是预留土堤对支护结构有减小其变形和内力的作用,甚至能够取代坑内的水平支撑,达到降低工程造价、缩短工期的目的,具有良好的经济效益、社会效益和环境效益。本文为了研究预留土堤对桩锚支护结构的影响,借助岩土工程专业的有限差分法分析软件——FLAC3D建立了桩锚支护基坑工程的三维数值模型,分别从有无预留土堤时支护桩和锚杆的反应、预留土堤宽度变化时支护桩和锚杆的反应以及高度变化时支护桩与锚杆的反应这三个方面进行分析。通过对不同工况下的计算结果进行对比分析,得到了如下结论：预留土堤的存在能够大幅增大其作用范围内地基土竖向应力,尤其是位于靠近基坑壁附近部位的地基土；预留土堤还能够降低支护桩的水平位移；预留土堤可以有效的减小支护桩的桩身弯矩,特别是在预留土堤的作用高度内,支护桩的桩身弯矩减幅最大,且对锚杆轴力也有大幅降低的作用,最大降幅达20%；随着土堤宽度的增加,支护桩的水平位移、桩身弯矩以及锚杆轴力也会逐渐减小,但是当其宽度增加到一定值时,对桩身弯矩、桩身变形以及锚杆轴力的降低效果就减弱了,因此需要根据工程实际确定一个合理的土堤尺寸；与增加土堤宽度相比,增加土堤高度能更加显著地降低支护桩的水平位移,并且随着土堤高度的增加,支护桩的桩身弯矩、预应力锚杆的轴力也会随之减小。更多还原

【Abstract】 In order to the sustainable development of cities,cities are gradually developing to the higher altitude and deeper undergroud,a lot of tall buildings and large-scale undergroud municipal constructions have been turnning up in central aeras of cities,so the development characteristics of deep foundation pit engineering are deep,large and close,and this also promote some new processes of deep foundation pit supporting. Pile-anchor support technology was created in1958,and in the1980s,it began to be applied to the deep foundation excavation of high-rise buildings in our country Because of its great applicability,huge technical advantage and enormous economic benefits,pile-anchor structure is widely used in the deep foundation pit construction in our county.Earth berm,a new pit constructing means,is also called as mound.when larger foundation pit is designed to use center island method to excave the pit,there will be earth berm in the pit.Among current foundation pit with earth berm as temporary supporting,earh berm is not a design factor considered during the pit design,but an meaning to control the derformation of supporting structure and the influence to surrounding environment.But earth berm can reduce the deformation and force of supporting structure,sometimes it even can replace the horizontal support in the pit,so that earth berm cut the project cost and shorter the construction period,which has great economic benefits,social efficiency and environmental efficiency.In order to study the effect of earth berm to pile-anchor structure,establish a3-dimention numerical model of pile-anchor supporting pit by finite difference analysis sofeware——LAC3D.In the thesis,effect of earth berm,influence change the width and height of earth berm lead to are analysed by quantification.According to caculation results of different working conditions,get the following conclusion:earth berm can greatly increase the foundation soil vertical stress within the scope of earth berm,especially near the pit walls;earth berm can reduce the pile’s displacement in the range from the height of earth berm to the bottom of pile;earth berm can effectively cut down supporting pile’s moment,especially in the height of earth berm decrease amplitude is the largest,and it also can reduce cable axial force,the largest decrease amplitude can reach to20%;as the increase of earth berm’s width or height,the horizontal displacement and moment of supporting pile,the cable axial force will gradually decrease,but when the width or height increase to a critical value,the decrease amplitude will be very small;compared with the increase of earth berm’width,the pile’s horizontal displacement will be obviously reduced by increasing earth berm’s height,and with the increase of the height,pile’s moment,cable axial force will descend.更多还原