真空预压联合塑料排水板堆载预压在工程中的应用

根据苏州白塘植物公园堆山工程地基的地质条件和设计要求,采用真空预压联合塑料排水板堆载预压的施工方案,对软土地基进行加固。监测结果表明真空预压联合塑料排水板堆载预压对软土地基进行加固处理切实可行。     

预压作用下软土固结蠕变及微观结构试验研究

为了揭示预压荷载作用下软土路基工后沉降的机理,开展了室内模拟真空、堆载以及真空—堆载联合预压加固软土的固结蠕变三轴试验及微观结构试验。分析了在三种不同的预压作用下土体固结蠕变性状的不同和微观结构的变化机理。结果表明:在三种不同的预压荷载作用下,固结过程中,是真空—堆载联合预压条件下土体的沉降量最大,其次是堆载预压,最小的是真空预压。蠕变过程的沉降量是堆载预压的最大,其次是联合预压,最小的是真空预压。预压荷载作用下土体的固结和蠕变具有耦合效应;微观结构参数的变化受预压加载方式的影响。微观结构参数的变化率与宏观物性参数的变化率有相似的性质。     

真空联合堆载预压软基加固机理分析及工程应用

结合珠江三角洲某高速公路真空联合堆载预压试验段工程,介绍了真空联合堆载预压法,分析了该法用于加固软弱地基的机理,重点阐述了真空联合堆载施工工艺流程及其设计要点.通过加固前后实测资料和软土土层土工试验结果对比表明,该法能在较短时间内有效地使珠江三角洲的深厚软土地基得到不同程度的加固,能缩短工期、消除工后沉降,达到节省投资的目的.     

联合预压方法加固软基的实例应用

结合宁波绕城高速公路第九标段工程实测资料，阐述了真空-堆载联合预压方法加固软土路基的施工工艺；进行了经济效益分析。指出在真空-堆载联合预压方法处理软土地基时建立科学的监测方法是控制施工质量的有效途径；得出的结论是：真空-堆载联合预压方法具有施工工期短、加固效果好、经济效益明显等诸多优点，将得到广泛应用。     

真空-堆载联合预压软基加固技术的应用

结合甬台温高速公路真空预压加固软土路基工程实例,介绍了真空-堆载联合预压的施工工序、方法,以及施工的成果,对真空-堆载联合预压加固高速公路软基的特点进行了分析,对高速公路路基施工有积极作用.     

真空联合堆载预压处理软土地基测试与分析

结合山东某港口大面积吹填软土地基处理实践,阐述了真空联合堆载预压施工相关监测和检测内容及其基本操作方法;分析了真空联合堆载预压施工过程中土体表面沉降、分层沉降、深层水平位移以及孔隙水压力的发展变化过程和规律。表明真空联合堆载预压法加固软土地基具有真空预压和堆载预压的双重加固特征,堆载能加速软土地基的固结变形,但在堆荷较小情况下,被加固土体总体仍表现为土体向加固区中心位移的收缩固结变形特征。从工后现场原位测试及试样室内土工试验成果可以看出,淤泥土层加固后含水量、孔隙比均有大幅减小,土体物理力学性质得到较大改善,土体强度增长幅度可达100%～300%。说明真空联合堆载预压应用于处理大面积吹填软土地基是成功可行的,其加固效果明显,有效影响范围可达排水板深度。     

真空-堆载联合预压处理深厚软土地基实录

文章给出了真空 -堆载联合预压处理深厚软土地基的全过程及施工、观测、效果检测与分析。工程实例表明 ,真空 -堆载联合预压处理深厚软土地基是一种快速、有效、经济的加固方法。     

堆载预压和真空堆载联合预压的比较

堆载预压和真空联合堆载预压都是工程中处理软土地基的常用方法。通过舟山富通电缆项目地基处理工程项目中堆载预压和真空联合堆载预压施工的比较研究,得出真空联合堆载预压比堆载预压具有更高的施工成效效率,更好的沉降稳定性和沉降性,以及水平位移量更小,使周围软弱边界的变形处于较为稳定的状态。     

真空-堆载联合预压加固设计及实践研究

以某市软土路基工程项目为研究背景,首先阐述当地的工程地质条件,然后结合真空-堆载联合预压加固机理对路基进行处理,分析了具体的设计方案和施工控制。最后通过现场试验的结果对地表沉降、水平位移等进行分析,探讨其应用效果。     

含承压水软基真空联合堆载预压加固试验研究

运用真空联合堆载预压法加固含承压水软基,简要介绍了防止承压水贯通的施工工艺。对港湾变电所软基加固试验中的地表沉降、分层沉降、土体深层水平位移和出水量等现场测试结果进行了分析。试验结果表明:真空联合堆载能有效消除含承压水层软基沉降,地基平均固结度为83%,工后沉降较小,能满足变电所软基工后沉降要求。对地基土体的加固效果进行了室内和现场试验。结果表明:真空联合堆载预压后土体的抗剪强度和承载力显著提高,加固效果十分明显。从单泵出水量和承压水层的压缩量来看,真空联合堆载预压过程中并未贯通承压水地层。加固后软基底部含水率比中部小,表明底部软土层向圆砾层排水加速软基固结。试验的成功进一步拓展了该法的应用领域,对类似地质条件下的真空联合堆载预压设计、施工和科研具有借鉴意义。     

真空堆载联合预压作用下软土地基位移和孔压变化规律研究

根据实测资料分析了真空堆载联合预压作用下加固区地表沉降、土体侧向位移、孔压、超孔压变化规律,并对孔压消散原因进行微观解释,结果表明:真空预压形成的负压与堆载预压形成的正压二者在加固软土地基的效果上是一致的,场地中心处的沉降要比四周大,用固结度对数配合法推定最终沉降,停泵时的平均固结度达到97%;真空预压阶段土体侧向位移方向是指向加固区内的,而堆载预压阶段是指向加固区外的;开始抽真空后浅层土体孔压消散非常明显,深层土体孔压消散较为缓慢,后期较深土层中孔压才有较大变化;超孔压在抽真空后变为负值,在真空预压阶段绝对值越来越大。     

Effect of vacuum removal on consolidation settlement under a combined vacuum and surcharge preloading

The combined vacuum and surcharge preloading technique is extensively used to accelerate the consolidation process of subsoils. The effect of vacuum pressure is often considered as a loading/unloading cycle of mean effective stress, such that elastic rebound occurs after vacuum removal, which cannot explain the observed postconstruction settlement in the field. In this study, the stress state of subsoils subject to vacuum and surcharge preloading is analyzed and decomposed into two components: (a) geostatic consolidation at a different depth, and (b) loading/unloading in the minor principal stress direction. A series of consolidated drained triaxial tests is conducted to simulate the soil behaviour after vacuum removal. Results show that the contribution of unloading in the minor principal stress direction outweighs the magnitude of elastic rebound after vacuum removal, and hence continued settlement dominates. A field case for highways is provided to further demonstrate the proposed mechanism.     

Comparative analysis on performance of vertical drain improved clay deposit under vacuum or surcharge loading

This paper presents two well-instrumented large-scale field tests of PVD-improved soft soil with vacuum and surcharge preloading, respectively. The two large-scale field tests were conducted adjacent to each other with the same preload. A comparative analysis was performed to investigate the performance of subsoil (i.e., the ground settlement, the layered settlement, the lateral displacement of subsoil and pore water pressure) under vacuum preloading and equivalent surcharge preloading. Some design methods were verified based on the field data. Cone Penetration Tests (CPT) and Vane Shear Tests (VST) were conducted to assess the improvement effects on subsoil after preloading. The results showed that as compared with surcharge preloading, vacuum preloading mitigated the differential settlement of the ground. The vacuum pressure transmitted into the soil with a minor loss through the PVD length. From a practical point of view, the improvement effects by vacuum preloading and surcharge preloading were similar in terms of influence depth and soil strength based on the in-situ tests.     

A simple solution for prefabricated vertical drain with surcharge preloading combined with vacuum consolidation

Prefabricated vertical drains (PVDs) with the surcharge preloading and vacuum consolidation has become considerably popular for ground improvement projects. A simple solution that incorporates the fundamental embankment features, such as the average degree of consolidation and excess pore pressure, are essential for the design of soft ground improvements by PVDs with vacuum preloading. However, most of the solutions for vertical drains with vacuum consolidation require numerical simulations, whose implementation tends to be laborious. In contrast, a simple solution for vacuum consolidation under time-dependent loading has not yet been proposed. In this study, a simple solution that can be easily incorporated into a conventional spreadsheet is derived for PVDs with vacuum preloading by applying the Laplace transform technique. The proposed solution accounts for several actual construction conditions, such as initial surcharge load, vacuum pump trial period, variations of radial permeability, and time-dependent loading. The results obtained from this proposed approach were validated with those from the finite element method and field data from the case study of the Cai Mep International Terminal project in southern Vietnam. The derived solutions, including the excess pore pressures and average degrees of consolidation, were in good agreement with the predicted and observed data.     

真空-堆载联合预压加固软基简化计算方法

在深入了解真空预压机理和砂井地基固结理论的基础上 ,根据固结度等效的原则 ,推导了与单井固结理论等效的成层均质地基等效渗透系数 ,从而将复杂砂井地基转化为无砂井成层地基 ,以达到简化计算的目的 ,并结合真空-堆载联合预压的加固特点 ,提出一种简化的真空-堆载联合预压法的有限元计算方法 ,并结合工程实例对简化方法的可靠性进行了研究 ,通过与实测资料和常规砂井地基有限元计算值对比 ,表明该简化方法具有较高的准确性 ,可方便地应用于工程设计和实践。     

含竖向排水体的软土路基固结分析

对含竖向排水体地基的固结理论进行了分析,研究了加载模式、竖向排水体间距及直径对软土路基固结的影响。结果表明,通过超载预压或者真空堆载联合预压可以较快地使软土固结,有利于减小工后沉降。     

沿海蚝塘回填区地基真空预压加固效果分析

结合珠海某蚝塘回填区真空预压软基处理工程,从现场监测和检测两方面分析了地基加固效果,结果表明：真空预压后,残余沉降、承载力均达到设计要求,软土各项指标明显改良,真空预压效果良好。