土工格栅控制液化土体流动变形的试验研究

液化导致的土体大变形以及侧向流动是地震引起建筑物破坏的主要原因。采用土工格栅作为主要加固材料,开展建筑物荷载作用下液化场地流动变形的振动台试验研究,考虑水平层状土工格栅、包裹状土工格栅和土工格栅+无纺布联合处理等3种加固方案对结果的影响,从超孔隙水压力发展、建筑物沉降量以及格栅应变特性等分析加固方案对液化变形的处理效果。试验表明:采用上述3种加固方案所得的相同埋深处超孔隙水压力峰值基本相等,表明土工格栅的加入基本不能改变地基的液化状态,而后期超孔隙水压力在土工格栅+无纺布联合加固方案下消散速度最快。与其它两种加固方案相比,土工格栅+无纺布联合加固方案下建筑物沉降量最小,相比未加固工况沉降量减少24%,土工格栅中间位置的应变峰值小于边缘位置的应变峰值。采用土工格栅+无纺布联合加固时,具有较大表面积的无纺布对该覆盖区域液化土体有较好的约束作用,限制了砂土颗粒的竖向移动。此外,砂土颗粒对无纺布的作用力将由土工格栅承担,这种作用力将有利于土工格栅与砂土之间的摩擦效应,进一步限制液化砂土的流动变形。

Experimental investigation on flow deformation of liquefiable soil reinforced with geogrids

The main causes for damage of buildings during earthquake are large deformation and lateral displacement of the soil induced by liquefaction. Using the geogrids as the main reinforcement materials, a series of shaking table tests are conducted on the liquefiable soil under the load of buildings in order to study the effects of different reinforcement schemes on the flow deformation of the soil. Three different reinforcement schemes are considered, including horizontal layered geogrids, package of geogrids, geogrids together with non-woven fabrics. The dvelopment of excess pore water pressure, the settlement of buildings and the strain properties of geogrids are obtained from the shaking table tests. The results show that the liquefaction behaviors of foundation soil can not be changed by the geogrids since the peaks of excess pore water pressure are equal at the same depth, but the excess pore water pressure dissipates more quickly for the reinforcement scheme with geogrids + non-woven fabrics. Compared with that of the other two kinds of reinforcement schemes, the settlement of buildings of the reinforcement scheme with geogrids together with non-woven fabrics is the smallest, which decreases by 24% of the settlement without reinforcement. Besides, the strain crest at the central position of the geogrids is less than that at their edge position. Using the geogrids + non-woven fabrics reinforcement scheme, the non-woven fabrics has better restriction on the liquefiable soil in coverage area because of its large surface, which limits the vertical movement of sand particles. In addition, the force between sand particles and non-woven fabrics will transfer to the geogrids, which will be beneficial to the friction between soil and geogrids. Finally, the friction can further restrict the flow deformation of liquefiable soil.