双面加筋土挡土墙外文文献翻译.docx

Mechanical performance of a double-face reinforced retaining wall in an area disturbed by mining
Abstract: The application of a double-face reinforced retaining wall during road construction can reduce engineering costs, speed road paving and have a good influence on environment. An ABAQUS numerical model of a double-face reinforced retaining wall was built. The influence of surface subsidence induced by mining was considered. A physical model test was also performed in the laboratory on a reinforced retaining wall. The influence' of subsidence induced by mining was observed. The numerical results match measurements in the laboratory very well. The vertical pressure on the base of the retaining wall, the horizontal displacement of the wall and the horizontal soil pressure acting on the wall were analyzed. The differential settlement of the reinforced belt and axial forces in the wall were also studied.
Keywords: double-face reinforced retaining wall; underground mining; finite element method; physical model test

1 Introduction
The road surface above a mining area will subside due to the work underground. Directly backfilling soil before sloping was adopted to reduce the influence of mining on surface roads. This method usually wastes land and is not reasonable economically. A doublefaced reinforced retaining wall does not need conventional sloping and therefore saves land. With mining, the road can be elevated using a double-faced reinforced retaining wall[11.
Many scholars have carried out preliminary studies on double-sided reinforced retaining wallst2~8]. Lei studied a double-sided reinforced retaining wall in a road project by using a centrifugal model test[9!. Displacements in a high double-sided retaining wall, the influence of different shapes of the retaining wall on displacements and the horizontal earth pressures acting on the retaining wall were studied. Zhu et al. studied displacements on the surface of the retaining wall, horizontal pressures acting on the retaining wall and the tensile forces in the reinforcing steel using test models[10l The retaining wall they studied met the condition B>Q.6H {B is the distance between the two walls and H is the height of retaining wall). No study has been carried out for a double-faced retaining wall under the influence of underground mining. The following shows the behavior of a double-faced retaining wall under the influence of underground mining by using numerical modeling.

2 Project background
There is a double-faced reinforced retaining wall in the mining area of Huainan. The reinforcement is flat steel strip; the panels are iron sheet and the back fill is coal gangue. The length of the double-faced retaining wall is 10 m and the height is 10 m. The wall is reinforced for a distance of 0.5 m. The cross section of the reinforcement is 0.2 mx0.002 m (Fig. 1).
3 Laboratory test for the project
Numerical results were compared to actual measurements during development of the project model. The ratio of the physical model dimensions to the actual dimensions is 20. Both the length and height of the model retaining wall are 50 cm. There were five displacement gauges on the left, and three on the right, for compensation. There were three pressure cells on the bottom of the retaining wall for measuring the variation in vertical pressure. Three pressure cells were on the flank to measure the horizontal pressure. Nine boxes were put under the soil. A jack was positioned under each box to control settlement (Fig. 2).

4 Numerical model
4.1 Description of the numerical model
The following assumptions are adopted in this study: The strain is assumed to be zero along the long-axial direction; all materials are assumed to be elastic; beam elements are used to model reinforced materials and blocks;the thickness of the surface soil is 10 m in the vertical direction; the horizontal dimension is 100 m; the double-faced reinforced retaining wall was centrally located on the top surface of the soil; the nodes along the outside vertical surfaces of the model are fixed in the horizontal direction for the soil; displacements are applied to the model bottom to simulate a negative curvature displacement, with a curvature radius of 100 m, and a vertical load was applied on the top of the retaining wall to simulate a traffic load (Fig. 3).
In addition, the panel and reinforcement are assumed to be elastic beam elements. The backfill and surface soil are assumed to be elasto-plastic. The Mohr-Coulomb model is employed using CPE8R elements. Reinforcing materials were embedded into the backfilled soil. The material parameters are shown in Table 1.
4.2 Verification of the model
The vertical stress on the bottom of the retaining wall was measured using conventional methods. Different subsidence of the bottom of the model did not have a significant influence on the stress induced in the retaining wall. Fig. 4 and Table 2 show the comparison between measured and modeled vertical stress at the bottom of the retaining wall. The simulated results matched the measurements reasonably well indicating that the numerical model was reasonable.
4.3 Numerical results
Horizontal displacement on the surface block Fig. 5 shows the horizontal displacement from subsidence of the soil caused by underground mining. As the soil subsides a horizontal displacement appears in the retaining wall. When a negative curvature formed at the bottom of the model an outward displacement occurred on the upper part of the retaining wall. When the curvature radius is 100 m the outward displacement on the top of the retaining wall is 0.06 cm; the inward displacement at the bottom of the retaining wall is -3.64 cm.
4.3.1 Horizontal stress induced by subsidence in the soil
Fig. 6 shows the stresses induced by soil subsidence. Differential subsidence reduced horizontal stress in the upper part of the retaining wall. At the same time the horizontal stress in the lower part of the retaining wall increased. This is because differential subsidence causes pressure on the upper part of the retaining wall to change from static to active while the soil pressure acting on the lower part of the retaining wall changes from static to passive soil pressure.
4.3.2 Horizontal displacement in the reinforced area of the retaining wall
Fig. 7 shows the vertical displacement induced in the reinforced area of the retaining wall by soil subsidence. The displacement is very small at the two ends of the retaining wall because it is influenced by the block area. In the middle part of the retaining wall the retaining wall moves with the soil. When the curvature is 100 m the differential settlement for layers 2, 6,10,14 and 20 are 1.87, 3.91, 5.34, 6.33 and 9.8 cm.
4.3.3 Axial stress induced by subsidence in the reinforced area
Fig. 8 shows the axial stress induced by subsidence in the reinforced area. When differential subsidence occurs, the maximum tensile stress occurs at the jointing part between the reinforced area and the block area. The maximum stress does not happen to occur in the cracked area15-61. Subsidence-induced axial stress along the length of the reinforced material is symmetrical in respect to the center of the reinforced area. The subsidence-induced axial stress in the lowest layer of reinforced material is much higher than that at the top of the reinforced material. The maximum subsidence-induced axial stress in the lowest layer of reinforced material is 27.6 MPa. The maximum subsidence-induced axial stress in the top layer is only 0.29 MPa.

5 Conclusions
1) The vertical stress acting on the base of the retaining wall increases in the middle while simultaneously decreasing at the two ends. The maximum subsidence-induced vertical stress on the base of the retaining wall is 98.1 kPa, which is double the weight of the soil itself.
2) An outward displacement of 0.06 cm occurs at the top of the block of the retaining wall. An inward displacement of -3.64 cm occurs at the lowest part of the block of the retaining wall. This implies that the soil pressure near the top of the block is in an active state and that the soil pressure decreases by 0.56 kPa. The soil pressure near the bottom of the block is in a passive state and it increases by 76.5 kPa.
3) Due to subsidence the reinforced area becomes curved symmetrically relative to the center of the retaining wall. The differential subsidence at the bottom of the reinforced area of the retaining wall is much greater that that at the top. The maximum differential subsidence is 9.8 cm.
Subsidence-induced stress change at the bottom of the reinforced area of the retaining wall is much greater than that at the top of the reinforced area. The maximum subsidence-induced stress is 27.6 MPa, which is one fourth of the tensile strength of steel.
6 Suggestions
When differential subsidence occurs in the future, the following measurements should be taken in the retaining wall.
1) A high-pressure splitting formed pile, or other methods, should be used to improve the ground soil for the soft soil.
2) Flexible block should be used if possible, or the density of reinforcing material increased, to decrease the horizontal displacement and stresses in the block of the retaining wall.
3) The bottom of the reinforced area of the retaining wall should be larger to get a bigger safety factor. At the same time, the joint area between the reinforced area and the block should be reinforced to avoid tensile stress induced cracking.
Through the above discussion , we have reinforced soil retaining wall type, structure , characteristics and working principle of understanding and mastering , enabling accurate placement and use of reinforced earth retaining wall

双面加筋土挡墙在采矿干扰区的机械性能
摘要：双面加筋土挡土墙的应用在道路建设中可以降低工程成本，节约资源，加快铺路速度以及对环境起到良好的保护作用。我们建立了一个双面加筋土挡土墙的ABAQUS数值模型。建模的同时考虑了地下采矿对土层的塌陷影响。与此同时在实验室里也对加筋土挡土墙的物理模型进行了实验，来观察由地下采矿活动引起的土层塌陷对双面加筋土挡土墙的影响。数值模拟的结果以及在实验室得到的实验数据都很好，我们对挡土墙基础的垂直压力，墙体的水平位移，以及作用在墙体的水平土压力一同进行了分析。还对墙体上加固区域的不均匀沉降以及墙体上的轴力进行了研究。
关键词：双面加筋土挡土墙，地下开采，有限元法，物理模型试验
1简介
由于采矿工作在地下进行，会直接导致上方路面下沉。在滑坡之前采用直接回填土壤可以减少矿物开采对地面道路造成的影响。但这种方法通常会浪费土地资源，而且在经济上也是不合理的。双面加筋土挡土墙并不需要传统意义上的斜坡，因此节省了土地。在采矿区，双面加筋土挡土墙可以使道路建的更高一些。加筋土的工作原理是拉筋与填土（通常是颗粒材料）之间的摩擦作用，可以解释如下：加筋土看作是由拉筋和土组成的一种复合材料。加筋土的工作原理是拉筋与填土（通常是颗粒材料）之间的摩擦作用，可以解释如下：加筋土看作是由拉筋和土组成的一种复合材料。三轴试验表明，对干燥的砂土试样施加竖向压力，试样会产生侧向膨胀；如果土中水平放置不易延伸的拉筋后，由于筋土的摩擦作用，使拉筋受到拉力，而给予土料的侧向位移以约束力，这就好象在试样上又施加一个侧向压力。当竖向压力增加时，侧向约束力随之增大，直到土与拉筋之间出现滑移或拉筋断裂，试样才破坏。因而，加筋土的强度相应获得提高。
许多学者都对双面加筋土挡土墙进行了初步的研究，雷教授在一个公路项目中用离心模拟试验研究了一座双面加筋土挡土墙。研究加筋土挡土墙的不同形状和作用于挡土墙上的水平土压力对双面加筋土挡土墙位移的影响。朱教授等人使用测试模型研究了挡土墙上的表面位移，作用于挡土墙的水平压力和丹图强内部钢筋的拉伸力。他们研究的挡土墙满足条件B > Q.6H（B是在两个壁之间的距离，H为挡土墙的高度）。但是没有人研究过在地下矿物开采时对双面加筋土挡土墙造成的一系列的影响。下面介绍了使用数值模拟的方法研究在地下矿物开采时对双面加筋土挡土墙各种影响。
2 工程背景
在淮南矿区有一座双面加筋土挡土墙。采用扁平钢带加固，面板是铁皮，回填土是煤矸石。
双面挡土墙的长度是10米,高度为10米。挡土墙被加强了0.5米的距离。该加强的部分横截面为0.2 mx0.002m .

3 实验室检验项目
项目模型的实验进行过程中用实际测量数据同数值模拟结果进行了比较。物理模型尺寸与实际尺寸的比例是1：20。模型挡土墙的长度和高度都是50厘米。有五个位移计布置在左边，右侧3个位移计，用做补偿器。有三个压力元件在放置在挡土墙的底部，用于测量挡土墙的基础的垂直压力的变化。三个侧翼的压力元件用来测量水平的压力。九个盒子一起放在土壤中。千斤顶是根据每个框的定位，以控制沉降（图2）。

4 数值模型
4.1模型描述
本研究采用以下假设：在沿长轴线方向应变近似被认为是零；所有材料被认为是弹性材料；梁单元被用来模拟增强材料和块; 土壤表层的厚度在竖直方向上是10米；水平尺寸为100米；双面加筋土挡土墙是位于土壤的顶面中心的区域；沿模型的外侧竖直表面的节点在土壤中被固定于在水平方向上；位移被施加到模型底部模拟负曲率位移，位移具有100μm的曲率半径，和一个垂直负荷施加在挡土墙的顶部，以模拟交通负荷（图3）
此外，面板和加固被假定为弹性梁单元。回填土和表面土壤均被假定为弹塑性土体。莫尔-库仑模型是通过CPE8R元素分析的。增强材料被嵌入到回填土中。材料参数示于表1中。

4.2验证模型
用常规方法测定挡土墙的底部的垂直应力。模型的底部的不同沉降并没有对挡土墙的应力有着显著影响。图4和表2显示在挡墙底部测量和建模的垂直应力之间的比较。模拟结果相匹配的测量表明该数值模型是合理的。

4.3数值结果
4.3.1表面块的水平位移
图5展示出地下开采所造成的土壤塌陷的水平位移。在土层下沉的时候挡土墙出现了水平位移。当一个负的曲率形成在模型的底部，挡土墙产生上部向外的位移。当曲率半径为100μm，挡土墙的顶部向外位移为0.06厘米; 向内位移的挡土墙的底部是-3.64厘米。
4.3.2土壤沉降引起的水平应力
图6显示出土壤塌陷引起的应力。不同沉降降低了挡墙上部的水平应力。在同一时间在挡土墙的下部的水平应力增加。这是因为差异沉降作用在挡土墙的上部，使稳定土压力变为主动土压力，而作用在挡土墙下部，使稳定土压力变为被动土压力。
4.3.3 挡土墙加固区的水平位移
图7显示了土层塌陷引起挡土墙土加固区垂直位移。位移是很小的挡土墙的两端，因为它受块区的影响。在挡土墙中间的部分墙体随着土层位移。当曲率为100m时，层2、6、10、14和20的不均匀沉降分别是1.87,3.91,5.34,6.33和9.8厘米。

4.34在加固区沉降引起的轴向应力
图8显示了加固区的沉降引起的轴向应力。当发生差异沉降时,最大拉应力出现在钢筋之间的接合部分区和块区。最大应力不会出现在破裂面积15 - 61。沉降引起的轴向应力沿着所述增强材料长度方向集中在区域的中心。沉降引起的增强材料的最低层的轴向应力远远高于在钢筋材料的顶部。最大沉降引起的轴向应力在增强材料的最低层是27.6兆帕。然而最大沉降引起的轴向应力在顶层却只有0.29兆帕。

5结论
（1） 垂直压力作用于挡土墙的基础上，中间增加，同时在两端减少。在加筋土挡土墙的基础上最大沉降引起的垂直应力是98.1 kPa,这是土壤本身重量的两倍。
（2） 挡土墙的顶部的块产生0.06厘米的向外位移。-3.64厘米的内在位移发生在最低的块挡土墙的一部分。这意味着块的顶部附近的土压力在处于活动状态时,土压力减少了0.56 kPa。块的底部附近的土压力处于一个被动的状态,它增加了76.5 kPa。
（3） 由于差异沉降，加强区域相对于挡土墙的中心变得弯曲对称。差异沉降在挡土墙的加固区域的底部是远远大于在顶部的沉降的。最大差异沉降竟然为9.8厘米
（4） 沉降引起的应力变化在挡土墙的加固区域的底部比在增强区域的顶部大得多。最大沉降引起的应力是27.6兆帕，这已经是钢材的抗拉强度四分之一。
6建议
当墙体在将来发生差异沉降时，首要的措施就是要在挡土墙进行测量。
（1） 用高压分裂形成桩，或者其他办法，来提高软土地基的地基承载力；
（2） 应尽可能使用弹性板块或增强材料的密度，以减小横向位移和挡土墙块的应力；
（3） 挡土墙的加固区域的在底部应该扩大一些，以此来获得一个更大的安全系数。在同一时间段内，增强区域和该块之间的接合面积应加大，以避免拉伸应力引起的开裂。
通过对以上内容的论述，我们对双面加筋土挡土墙的型式、构造、特点和工作原理有所了解和掌握，从而能够准确的布置和使用双面加筋土挡土墙。