水平联合竖直排水板真空预压处理工程废浆试验研究

传统真空预压法(VP)在加固工程废浆时存在预制竖向排水板(PVD)易淤堵、周围土体形成土柱以及真空度随深度衰减等问题,考虑到预制水平排水板(PHD)在真空预压法处理软土地基中的特点,提出一种水平联合竖直排水板真空预压(PHD-PVD-VP)处理工程废浆的方法。通过4组大型室内模型试验,对工程废浆加固过程中的排水、沉降以及孔隙水压力进行监测,并借助扫描电镜得到的排水板滤膜微观图片,分析不同初始PHD真空压力下PHD-PVD-VP对工程废浆的加固效果。试验结果表明,PHD-PVD-VP处理工程废浆时减少了土颗粒径向移动速率,延缓“土柱”的形成及缓解土颗粒嵌入排水板滤膜的淤堵效应,提升了土体整体固结效果;40 kPa的初始PHD真空压力使PHD-PVD-VP对工程废浆的排水固结效果最佳,处理后土体的平均含水率和十字板剪切强度分别为40.9%和25.5 kPa,有效地缓解了PHD和PVD的淤堵并改善了土体固结的均匀性。通过微观结构分析发现,PHD初始真空压力的大小同时影响着PHD与PVD滤膜的淤堵情况,从而影响其排水性能,40 kPa的初始PHD真空压力使得两种排水板的排水性能都得到充分发挥。

Experimental study of waste slurry treated by a vacuum preloading method combined vertical drains with horizontal drains

When the vacuum preloading (VP) is used to consolidate the engineering waste slurry, there are several problems, such as the clogging of prefabricated vertical drain (PVD), formation of the soil columns and the attenuation of vacuum degree with depth, resulting in non-uniform consolidation. Considering the characteristics of prefabricated horizontal drain (PHD) in the treatment of soft soil foundation by VP method, a vacuum preloading method combined PHD with PVD (PHD-PVD-VP) is proposed to treat the slurry. Through four groups of large-scale indoor model tests, the drainage, settlement and pore water pressure during consolidation of engineering waste slurry were monitored, combined with the micro pictures of drainage board filter membrane obtained by scanning electron microscope, the consolidation effect of PHD-PVD-VP on engineering waste slurry under different initial PHD vacuum pressures was analyzed. The test results show that the PHD-PVD-VP reduces the radial movement rate of soil particles, delays the formation of "soil column", alleviates the silting effect of soil particles embedded in the filter membrane of drainage plate, and improves the overall consolidation effect of soil; initial PHD vacuum pressure of 40 kPa makes the drainage and consolidation effect of PHD-PVD-VP on engineering waste slurry the best, the average water content and vane shear strength of the treated soil were 40.9% and 25.5 kPa respectively. It not only effectively avoids the clogging of PHD and PVD, but also improves the uniformity of soil. Combined with the microstructure analysis, it is found that the initial PHD vacuum pressure affects the clogging of PHD and PVD filter membranes simultaneously, so as to affect their drainage performance. The initial PHD vacuum pressure of 40 kPa gives full play to the drainage performance of the two drainage boards.