软土路基排水固结法滑塌原因及处治

Analysisand Treatment ofLandslide of Soft Soil Subgrade withDrainage Consolidation Method

依托广东某高速公路K23+217~+357段袋装砂井+堆载预压法软基处理,对该路段施工过程中路堤失稳的原因进行了分析,并采用有限元法对施工过程及滑塌后采用反压护道处治的方案进行了计算分析。结果表明:采用排水固结法处理软土路基,路堤填筑的初期可适当提高荷载填筑速率以节约工期,并及时施加预压荷载争取预压时间;路堤填筑后期,施加荷载应小于软土固结强度的增长,严格控制荷载施加速度;路堤设置反压护道后,路堤的潜在滑动面呈现“圆弧+直线+圆弧”或由两个圆弧组成近似“W型”的型式,与反压护道的高度及软土层厚度等因素相关,因此对设有反压护道的情况仅采用圆弧滑动法计算其稳定性欠妥,稳定性计算可采用有限元强度折减法;反压护道对路堤沉降影响较小。排水固结+反压护道方案可提高排水固结法应用的极限高度,是经济有效的软基处理方案之一。

Being based on soft soil subgrade treatment with drainage consolidation method with sand well of K23+217~K23+357 Section of a highway in Guangdong Province, the reason of embankment sliding failure in the construction process of this section has been analyzed. The finite element method has been used to calculate and analyze the construction process and the treatment scheme of back berm after sliding failure. The results have shown that: In the treatment of soft soil subgrade with drainage consolidation method, in the initial stage of embankment filling, the embankment loading rate can be appropriately increased to save the preloading period, and the preloading load can be applied in time to gain the preloading time. In the later stage of embankment filling, the loading should be less than the increase of soft soil consolidation strength, and the loading speed should be strictly controlled. The potential sliding surface of the embankment with back berm presents a “arc+straight line+arc” or approximate a “W shape” formed by two arcs, which is related to the height of the back berm and the thickness of the soft soil layer. Therefore, it is not appropriate to use the arc sliding method to calculate the stability of embankment with back berm, and the finite element strength reduction method can be used to calculate its stability. The influence of back berm on embankment settlement is small. Drainage consolidation method with back berm can improve the limit height of drainage consolidation method, and it’s an economical and effective treatment for soft soil subgrade.