浅议预压法解决软土地基工后沉降

介绍了软土地基沉降推算方法,阐述了排水固结法配合预压法解决工后沉降的方法,分析了土体固结与超载量、超载作用时间等因素的相关关系,提出结合土体固结性质,增加卸载考核指标的建议。     

超载预压技术加固高速公路软基的试验研究

为了解超载预压技术对深厚软土的加固效果,结合杭州湾跨海大桥南岸接线高速公路试验段工程,对超载预压技术处理的试验断面进行长达2 a多的现场试验测试。实测结果表明,处理后的路基工后沉降小于15 cm,满足设计要求小于30 cm的标准;深层压缩主要是在排水板范围内的土体中完成的;侧向位移主要发生在16 m以上部位,且7 m以上土体是向加固区内移动的,7 m以下则向加固区外移动;加固后期,加固区表面的断面沉降呈明显的锅底形;孔隙水压力变化在较浅的土层受影响明显,反应灵敏,而深层则反应较慢,孔隙水压力变化不剧烈;原位十字板测试以及室内土性试验结果表明,加固后的土性物理指标有明显的改善,土的工程力学性质有显著增强,说明超载预压排水固结法加固软土地基达到预期的目的,在类似路段中应用是可行的。     

厦门某滨海大道软基处理实践

采用袋装砂井超载预压法及粉喷桩法加固滨海相淤泥及淤泥质土路基,在采取严格的现场监测控制下取得了良好的加固效果。     

真空预压法加固潮间带软土地基的试验研究

针对潮间带的地质特点,采取真空预压法联合塑料排水板加固处理潮间带软土地基。试验结果表明,加固区内地下水位下降2.98～4.17m,而区外8,12m处的水位降深最大值分别只有0.78,1.04m。塑料排水板内的负孔隙水压力比较均匀,约为膜下真空度的90%,传递深度可达到13m以上,说明有效加固深度大于10m。淤泥中的负孔隙水压力则较小,其数值大小主要取决于所处位置的软土特性。加固后软土的物理力学性质指标有较大的改善,含水量一般可降低10%～20%,重度提高约10%,孔隙比减小10%～30%。加固区内软土强度得到较大提高,排水板区中间强度平均提高73%～75%;加固后随着地基土体静置时间的延长,土体强度仍有一定程度的增长,平均增长率为0.6%/d,说明加固效果良好,真空预压对潮间带同样适用。     

塑料排水板法在软土地基处理中的设计与施工

根据广州东沙至新联高速软弱大层的工程特性,提出采用排水固结法作为处理方案,并对堆载计划的确定和堆载方案进行了阐述,介绍了回填施工过程中地基处理的施工要求,从而明显地改善了本工程软土层的排水固结过程,使得整个工程得以顺利进行。     

真空联合堆载预压法的边界效应及其影响因素

介绍了真空联合堆载预压法的边界效应,并通过真空联合堆载预压法加固机理、应力路径及强度增长,阐述了产生边界效应的原因,讨论了造成加固区边界效应的影响因素,最后提出了对加固区边界效应的防治措施。     

Analytical solutions to the axisymmetric consolidation of a multi-layer soil system under surcharge combined with vacuum preloading

Surcharge combined with vacuum preloading is a common technique for accelerating the consolidation process in ground improvement. A unit cell model for the axisymmetric consolidation of a soft soil using a prefabricated vertical drain (PVD) under a surcharge, combined with vacuum preloading, is investigated in this study. Based on this model, analytical solutions for a multi-layer soil system are put forward and the explicit expressions for two-layer and one-layer systems are presented. The accuracy of the proposed solution is verified using an analytical solution available in the literature. In the parametric study, the influencing factors on the consolidation process, such as, the smear zone, the PVD spacing, the hydraulic conductivity in the radial direction, the coefficient of vacuum decrease, are taken into account. The water flow in the radial direction plays an important role in the consolidation process while the impact of the vertical flow mainly develops around the interfaces between two adjacent layers. In addition, the proposed analytical solution is applied in a case history with three different layers and the results are reasonable.     

袁家村铁矿湿陷性黄土地基建尾矿坝的研究与应用

我国湿陷性黄土分布广阔,在湿陷性黄土地区建设尾矿库应考虑湿陷性黄土地基对坝体的影响,通过局部挖除、堆载预压、反压坡脚、滤水疏干等一系列工程措施,保证坝体的安全稳定。     

深海沉管隧道基础水下沉降监测技术

为消除管节间差异沉降,港珠澳大桥岛—隧过渡段沉管基础采用挤密砂桩+堆载预压的地基处理方式。详细介绍了采用液体压差式沉降仪监测沉管隧道基础沉降的应用技术,并获得了较好的复合地基沉降数据。采用多种技术手段保证仪器埋设成功率,包括作业时机选择、导线接头及导线保护等。对试验结果进行分析,结果表明该技术运行稳定性高、数据误码率低、不易受风浪及施工干扰,可实现对沉管基础的连续稳定无线监测。     

Vacuum Preloading Combined with Electro-Osmotic Dewatering of Dredger Fill Using Electric Vertical Drains

Based on the vacuum preloading combined electro-osmotic consolidation method, a site comparison trial of vacuum preloading and vacuum preloading in combination with electro-osmotic consolidation was performed on Li Island, Hubei Province. The performance and drainage effects of electric vertical drains were evaluated. The problems were analyzed by monitoring test results. Test results from the field showed that the water content of the dredger fill was greatly reduced and the physico-mechanical properties and bearing capacity were improved significantly after 28 days of treatment by vacuum preloading in combination with electro-osmotic consolidation. Compared with the vacuum preloading method, vacuum preloading in combination with the electro-osmotic consolidation method using electric vertical drains reduced the construction time, saved energy, and achieved an ideal reinforcement effect.