不同面板形式加筋土挡墙结构特性现场试验研究

以成昆铁路复线加筋土挡墙为工程依托进行现场原位试验,对比分析工后9个月内新型整体式面板、内嵌返包结构的模块式面板和模块式面板3类加筋土挡墙的结构特性。在此期间发生两次地震,监测了震后挡墙变形及土压力变化。结果表明:整体式面板加筋土挡墙整体稳定性最好,具有良好的抗震性能,格栅应变变化率、墙体压缩量和墙面水平位移均最小。整体式面板和模块式面板加筋土挡墙墙背土压力沿墙高近似呈M型,内嵌返包结构的模块式面板加筋土挡墙墙背土压力沿墙高近似呈倒S型。整体式面板加筋土挡墙的侧向土压力系数沿墙高变化较小,小于美国联邦公路局(FHWA)加筋设计指南计算值;内嵌返包结构的模块式面板加筋土挡墙侧向土压力系数沿墙高呈增大的趋势,挡墙中、下部小于FHWA计算值,上部接近或大于静止土压力系数;模块式面板加筋土挡墙侧向土压力系数大部分处在FHWA计算值与静止土压力系数之间。3类挡墙土工格栅应变沿墙高均呈非线性变化。挡墙墙体压缩量随着时间的增加逐渐增加,在工后前50 d时间内增加速率较快,随后增加速率减缓,进入雨季之后增加速率再次增大。发生地震后,3类加筋土挡墙均出现不同程度的墙背土压力减小、格栅应变增大、墙体压缩量增加和墙面板外移的现象。

Field tests on structural properties of reinforced retaining walls with different panels

Based on the reinforced retaining wall of Chengdu-Kunming railway, the field tests were carried out. The comparison of the reinforced retaining wall with full-height rigid panels, the reinforced retaining wall with modular panel embedded return package structure and the reinforced retaining wall with modular panel within 9 months after the completion of construction were analyzed to study the structural properties. During the test period, two earthquakes occurred and changes of the deformation of retaining wall and the earth pressure were monitored. The results show that the geogrid strain rate, wall compression and wall horizontal displacement can be well controlled by the reinforced retaining wall with full-height rigid panel, showing the best stability and seismic performance. The earth pressure on the back of the reinforced retaining wall with full-height rigid panel and reinforced retaining wall with modular panel are distributed following with a "M" type along the wall height. The distribution of earth pressure on the back of the reinforced retaining wall with modular panel embedded return package structure is similar to "S" along the wall height. The lateral earth pressure coefficients of the reinforced retaining wall with full-height rigid panel change little along the wall height, which are less than the FHWA calculated values. The lateral earth pressure coefficients of the reinforced retaining wall with modular panel embedded return package structure have an increased trend along the wall height. The values of the middle and lower part of the retaining wall are less than the FHWA calculated values, and the values of the upper part are close to or higher than the static earth pressure coefficients. Most of the lateral earth pressure coefficients of the reinforced retaining wall with modular panel are ranging from the FHWA calculation values to the static earth pressure coefficients. The geogrid strains of three retaining walls change nonlinearly along the wall height. The retaining wall compressions increase gradually with the increased time, especially in the first 50 days. Then the increase rates gradually decrease until the coming of the rainy season, the hydraulic effect promotes the increase rates to increase again. After the earthquakes, the earth pressure on the back decreases, the geogrid strain increases, the wall compressions increase and the wall panels have an obvious trend to move out.