大型厚层滑坡多锚点预应力锚索抗滑桩

滑坡,作为一种重要的地质灾害,它的出现往往会造成交通中断、河流堵塞、厂矿摧毁、村庄和农田破坏,形成巨大的人员伤亡和经济损失,由于其产生的条件、作用因素、运动机理的多样性、多变形和复杂性,滑坡的预测困难,治理费用呈越来越昂贵的趋势。因而滑坡的研究和治理成为各国学者所关注的重要地质和工程问题之一。抗滑支挡结构作为治理滑坡的主流工程措施,从上世纪50年代以来得到广泛应用,其结构形式从普通挡土墙到各种截面形式的抗滑桩;从锚杆、锚索到锚索框架、锚索抗滑桩;桩的结构形式有矩形、圆形;也有钢架桩、排架桩、椅式桩墙、微型群桩、小型钢桩等,形式繁多、不胜枚举。1967年,抗滑桩在我国沙北滑坡采用以来,因其具有开挖面小、对滑坡稳定扰动少、抗滑能力强、开挖土石方量较小及设置位置灵活等优点,得到广泛的应用。但由于其结构属大悬臂受力结构,桩身内力大,滑面以下埋深达整个桩身的五分之二至二分之一,从而耗费大量的钢材和水泥,工程造价高。为了从根本上改变普通抗滑桩不合理的悬臂受力状态,中铁西北院从1986年起,经过三年多试验研究,成功地研制出预应力锚索抗滑桩新结构,即从靠近桩顶部位加设锚索,并施加预应力,从而改变了悬壁桩身的受力状态,类似于简支梁,大大减小了桩身弯矩、截面积和埋深,工程造价节约了25%～50%,因而很快得到推广使用。本文在滑坡稳定性判定和滑坡推力计算的基础上,以北京戒台寺滑坡整治工点为依托,对单锚点预应力锚索抗滑桩进行设计优化,提出了多锚点预应力锚索抗滑桩新结构;用有限单元法分析了不同推力情况(小、中、大等级滑坡推力)下普通抗滑桩、单锚点抗滑桩及多锚点抗滑桩内力分布,进行了力学比较;并综合考虑了工艺、造价及整治效果等因素,对普通抗滑桩、单锚点抗滑桩和多锚点抗滑桩三种结构形式进行了综合指标比较;论文还对依托工点,戒台寺滑坡治理应用多锚点锚索抗滑桩的设计优化方法及施工工艺进行了总结;并在滑坡地表及深部孔位进行地表和地下位移监测,在锚索中设置荷载传感器和抗滑桩钢筋中设置钢筋计,对锚索拉力和桩的钢筋受力进行测试,对测试数据进行分析、对比和拟合验证;论证应用预应力多锚点锚索抗滑桩结构的整治效果及抗滑结构物的受力特征。在大推力(大于3300kN/m)情况下,通过造价比较,得出了多锚点锚索抗滑桩比普通桩节省造价34.9%,比单锚点桩节省11.9%的结论,可见多锚点桩的经济效益非常明显,是一种很有前途的抗滑桩新结构形式。论文创新点:1通过利用有限元对预应力锚索抗滑桩桩身内力计算,得出了适用于多锚点预应力锚索抗滑桩的滑坡条件;2提出了多锚点预应力锚索抗滑桩最佳锚索位置的优化方法;3提出了关于确定多锚点预应力锚索抗滑桩锚索最佳设计拉力范围的方法;4提出了一套关于多锚点预应力锚索抗滑桩结构设计优化方法。
活动房
Landslide, as a main kind of geological hazards, often stops traffic, blocks rivers and destroys factories, mines, villages and farmland. It causes great loss to the human life and property. Owing to the varied, changeable and complicated developing conditions, acting factors, and movement mechanism, it is very difficult to forecast the occurrence of landslide and the cost for prevention and control is more and more expensive. So, the study and control of landslide have become one of the important geological engineering problems concerned by the scholars in China and abroad.As the main engineering measure for controlling landslide, the anti-slide retaining structure has been widely used since 1950’s. It includes normal retaining wall, anti-slide pile with rectangle and circular cross sections, anchor rod, anchor wire, anchor wire frame and anchor wire anti-slide pile as well as bent pile, h-like pile wall, mini-pile cluster, small steel pile and pile with anchor wire, etc.The anti-slide piles have been used widely with the advantages of small excavation face, powerful anti-slide capacity, less cubic meter of excavation stone and flexible location since it was used for controlling Shabei landslide in 1967. Because the structure is a large cantilever force-subjected one, the internal force is large in the pile shaft and the depth of embedment beneath the sliding plane reaches l/2to 2/5 of the whole shaft, so that great deal of steel and cement are used and the cost is expansive. In order to improve the state of unreasonable force subjected by cantilever of the normal anti-slide piles, Northwest Research Institute of CREC successfully developed pre-stressed anchor-wire anti-slide pile in 1989 through the studies for more than three years. The anchor wire is added near the top of pile and pre-stress is exerted. It seems to set up a twist fulcrum, the state of force-subjected is similar to that of the beam with simply supported ends and the cost of engineering is reduced by 50%-25%. So the new structure is spread quickly and used widely.This paper, on the bases of the stability judgment and thrust calculation of landslides, optimizes the design of pre-stressed anchor-wire anti-slide pile with single anchor point and puts forward the new structure of pre-stressed anchor-wire anti-slide pile with multi-anchor points. It analyses, by using FEM, the distribution of internal force of normal anti-slide pile, anti-slide pile with single-anchor point and with multi-anchor points at the conditions of varied force-subjected (small, middle and large thrust of landslide), compares the mechanics, considers comprehensively the factors of technique, technology, distribution of internal force and cost, and carries out the comparison of the above mentioned three structures. It summarizes the methods of optimized design and construction technology of anchor-wire anti-slide pile with multi-anchor points used at Jietaisi landslide, analyses, compares and verifies the test data, and demonstrates controlling effect and characteristics of anti-slide structures subjected to force on the bases of the monitoring of displacement and deformation carried out at the ground surface and deep hole location of the landslide and tests on the tensile stress of anchor wire and the stain of pile.It is economical and rational to adopt the pre-stressed anti-slide pile with multi-anchor points at the condition of large thrust (more than 3300kN/m), and the cost of pile with multi-anchor points is reduced separately by 34.9 % and 11.9% as compared with that of the normal pile and pile with single anchor point. It is obvious that the pile with multi-anchor points is a new economical structure with great future.New ideas of the paper:1. It puts forward the landslide conditions of pre-stressed anchor-wire anti-slide pile with multi-anchor points through the calculation of internal force in pile using FEM.2. It puts forward the optimum method for the best place of anchor wire of pre-stressed anchor-wire anti-slide pile with multi-anchor points.3. It puts forward the best design method to determine tensile range of anchor wire of pre-stressed anchor-wire anti-slide pile with multi-anchor points.4. It puts forward the method to optimize structure design of pre-stressed anchor-wire anti-slide pile with multi-anchor points.