软土地基堆载吹填淤泥并同步真空预压加固技术探讨

针对软土地基上吹填造陆工程中真空预压法加固软土地基和吹填淤泥工期较长、效果较差的问题,提出了堆载吹填淤泥并同步真空预压加固技术,将吹填淤泥加固及软土地基加固两阶段施工整合到一个真空预压周期内完成,大幅度缩短了造陆工期。通过实验发现,该技术能够有效地解决常规真空预压法中上部吹填淤泥导致变形过大使得加固效果降低的问题,充分利用地基本身重力作用,不需要额外的材料就能够完成软土地基处于真空联合堆载预压的加固模式,显著地提高了加固效果。     

吹填淤泥在真空联合堆载预压过程中的工程性质变化特征

本文以深圳前湾A区真空联合堆载预压处理吹填淤泥的工程为例,采取室内试验和原位测试分析,详细地研究了吹填淤泥在砂垫层施工阶段、插塑料排水板后加载前阶段、联合堆载前纯真空预压阶段、真空联合堆载预压阶段的工程性质变化特征,随着施工推进,吹填淤泥的含水量和孔隙比逐渐降低,湿密度和干密度逐步增加,吹填淤泥土性质不断得到改善,强度持续增加。最后,对真空联合堆载预压达到设计卸载标准后的吹填淤泥加固效果进行了检测和分析,结果表明加固效果达到了设计要求,为吹填淤泥的处理提供了借鉴作用。     

吹填淤泥真空预压加固效果分析

结合天津某吹填淤泥真空预压处理工程,分析了吹填淤泥沉降、水平位移及孔隙水压力消散变化特点,并结合加固前后室内土工试验和现场十字板剪切试验对真空预压的加固效果进行了对比分析,试验结果表明:加固后吹填淤泥的物理力学性质指标及现场十字板试验结果均得到大幅度提高。     

真空预压在大面积吹填软土地基处理中的应用与研究

天津临港造修船基地通过围海造陆而成,吹填物料为海底淤泥。为提高地基承载力,该工程采用真空预压法进行地基处理。通过工程实践证明：真空预压法对软土地基加固效果好,可适用于较大面积吹填软土的加固施工。     

真空预压技术在温州地区吹填淤泥地基加固中的应用

吹填造陆是解决土地资源紧缺的有效途径,以温州民科基地永兴北园吹填淤泥地基处理工程为例,采用真空预压技术加固新吹填淤泥地基,介绍了该技术的施工工艺,分析了现场管理的要点和注意事项,并进行了现场监测及检测工作。结果表明,浅层加固技术可使新吹填淤泥层在较短的时间内获得良好的加固效果,土体含水量和孔隙比大幅度减小,表层承载力明显提高。该技术可节省地基处理工期和工程成本,在大面积超软弱地基处理工程中有着广阔的应用前景。     

吹填淤泥土的固结特性研究

介绍了大型围海吹填造陆工程中,采用堆载预压与真空堆载联合预压法加固处理吹填淤泥与原状淤泥的工程实例。对该工程B2场地吹填淤泥落淤与软基处理前后物理力学性质、吹填淤泥与原状淤泥的压缩变形、孔压与真空度测试结果进行分析。结果表明：吹填淤泥经晾晒与自重固结作用,物理性质得到大大改善,表层0～1m平均含水量与孔隙比明显小于下层...     

粉煤灰生石灰加固吹填淤泥质土的试验研究

在吹填淤泥质黏土中掺入不同比例的生石灰和粉煤灰,对不同掺入比的固化土进行无侧限抗压强度试验,分别测定不同龄期固化土强度。根据结果分析加固效果、确定合理的掺灰比,并与常用固化剂比较加固效果。结果表明,当生石灰的掺量一定时,粉煤灰的掺量在15%左右时无侧限抗压强度达到峰值,粉煤灰掺量一定时固化土无侧限抗压强度随着生石灰掺量增大而增大。替代水泥、生石灰等常用固化剂,采用掺入15%粉煤灰与10%生石灰混合固化剂加固吹填淤泥加固效果明显,粉煤灰与生石灰混合加固是一种既经济又环保的加固吹填淤泥方法。     

常州车站铁路罩棚的软基加固

结合在常州火车站淤泥吹填区建设一座轻钢结构火车铁路罩棚的工程实例,通过对建设前期吹填区软弱地基加固、建设完工后进行检测试验,总结设计、施工和检测等实际经验。     

多水塘区域路基吹填砂施工技术

吹填砂施工可以高效连续作业,有效加快施工进度,解决土资源紧缺和运输问题;但由于施工需要大量的水,因此吹填砂施工项目周边需有丰富水源。在多水塘区域进行路基吹填砂施工时,应注意采取措施处理水塘淤泥,清淤后应对吹填砂施工基础进行加固,确保施工质量。本文通过具体施工项目讨论在多水塘区域进行路基吹填砂施工工艺和应注意的问题。     

多水塘区域路基吹填砂施工技术

吹填砂施工可以高效连续作业,有效加快施工进度,解决土资源紧缺和运输问题;但由于施工需要大量的水,因此吹填砂施工项目周边需有丰富水源。在多水塘区域进行路基吹填砂施工时,应注意采取措施处理水塘淤泥,清淤后应对吹填砂施工基础进行加固,确保施工质量。本文通过具体施工项目讨论在多水塘区域进行路基吹填砂施工工艺和应注意的问题。     

真空联合堆载预压处理深厚软土效果分析

软土由吹填土和原状淤泥质土构成,平均深度为25m,且表层覆盖回填土层,采用真空联合堆载预压法进行处理。检测结果表明,该场地表层承载力达到100kPa以上,下部淤泥质土层承载力达到80kPa,平均沉降153.14~202.79cm,加固效果非常明显。实践证明,针对该区的深厚淤泥质软土地基,真空联合堆载法具有加固效果好、工期短和施工安全等优点,值得在该地区工程建设中推广应用。     

深圳机场中心变电站地基处理沉降监测分析

深圳机场110/10KV中心变电站建在填海场地之内,该场区淤泥平均层厚9.5m,具有高含水量、高压缩性、极低强度、欠固结等特点。采用排水板+堆载预压的方法对该软土地基进行处理,对整个施工和预压过程进行了全程监测,监测数据显示地基土性质明显改善,工后沉降满足设计要求。     

Effects of pressurizing timing on air booster vacuum consolidation of dredged slurry

Air booster vacuum preloading is a newly improved method applied in land reclamation projects. Highly pressurized air can provide an additional pressure difference between the prefabricated vertical drain (PVD) and injection point, thereby increasing the hydraulic gradient and generating small fractures that can improve the soil permeability and the transmission efficiency of the vacuum pressure. However, with a premature activation time, the pressurized air can create air channels connected to the PVD, which may drastically decrease the vacuum pressure. With a delayed activation time, the strength of the dredged clay may be too high to permit fractures, thus limiting the permeability improvement. In this study, soils with degrees of consolidation (DOCs) of 0%, 40%, 60%, and 80% were selected for testing the efficacy of initial booster activation times in four tests. The results show that the pressurizing groups were more effective in improving the consolidation of soils, and the best effect of the use of air booster is obtained when soil has been consolidated to a DOC of 60%. The lower soils of the pressurized groups showed greater increase rates than those demonstrated by conventional vacuum preloading.     

Pilot tests on vacuum preloading method combined with short and long PVDs

Dredged marine clay has been widely used as a filling material for land reclamation in China. The difficulty of using the vacuum preloading method to improve the dredged marine clay together with the bottom sediment clay is the different spacing requirement of the PVDs. To solve this problem, the Vacuum Preloading method combined with the Short and Long PVDs (VPSL) is proposed in this paper. The short PVDs are installed only into the dredged marine clay layer in-between the long PVDs which are installed through the whole clay layer. Pilot tests are also conducted at a land reclamation site in Tianjin, China, to investigate the performance of the proposed method. The ground settlement, the applied vacuum pressure and the pore water pressure in the soil are monitored during the pilot tests. The average degrees of consolidation are calculated based on the monitored settlement and pore pressure data. It is found that the proposed VPSL method is more effective for improving top dredged clay together with the bottom sediment clay than the conventional vacuum preloading method. The vane shear strength profiles of soil layers after ground improvement also show that the VPSL method is more effective to achieve a uniform soil strength profile.     

Experimental study of PVD-improved dredged soil with vacuum preloading and air pressure

The PVD-vacuum method is the main method used to treat dredged soil, but sometimes it cannot completely meet engineering needs due to the limitations of vacuum pressure. Therefore, based on the traditional PVD-vacuum method, a method of air pressure combined with vacuum preloading is proposed in this paper. The air pressure is transmitted into the dredged soil by using an impermeable and flexible membrane airbag embedded in the dredged soil. A comparison of the traditional PVD-vacuum method and the combination of air pressure and vacuum preloading is investigated by the model test. The data of the settlement and water discharge during the test are monitored. After the tests, the water content and shear strength at different positions are measured. Finally, a method for calculating the volume change of dredged soil is proposed, and the results of the test are used to prove the correctness of the proposed method.     

Experimental study on a dredged fill ground improved by a two-stage vacuum preloading method

The vacuum preloading method has been wisely chosen among many ground-improvement methods considering the time limit of many projects and the characteristics of reclaimed soil. However, the loss in vacuum with soil depth, the clogging around prefabricated vertical drains (PVDs), and the deteriorative consolidation of the deep soil layer, among other factors, create a large challenge to vacuum preloading for dredged marine clay fill. Thus, this study proposes a two-stage vacuum preloading method and focuses on its feasibility and effectiveness. Contrasting laboratory tests are performed in two identical experimental tanks with dredged marine clay fill from the Wenzhou land reclamation site in China. In one tank, the one-stage vacuum preloading method is used to serve as a baseline for this study. In the other tank, use of the two-stage vacuum preloading method is proposed for consolidation; it comprises two stages. In the first stage, the dredged marine clay fill is conditioned by vacuum preloading using half of the PVDs, where the dissipation of the excess pore water pressure tends to be steady. In the second stage, vacuum preloading is activated using all the PVDs. The results show that a better consolidation effect is achieved with the proposed method in terms of the settlement, vacuum pressure, pore water pressure, water content, vane shear strength, and soil particle microstructure after soil consolidation.     

真空覆水预压处理房建软基效果评价

针对深厚软基的房建项目在后期使用过程中因仅对主体建筑进行地基处理而引起的差异沉降、甚至主体结构开裂倾斜等病害;采用真空联合覆水预压法对某房建项目之深厚软基进行前期处理,并从理论计算、现场施工、施工监测、工后检测等方面对该工法进行分析,认为真空覆水预压法处理房建项目深厚软基可以消除后期项目运行过程中的差异沉降等问题。该工法处理房建项目深厚软基可满足设计要求、施工方便、工期较短、且可消除以往直接采用桩基处理等方法产生的病害、切实可行、值得推广应用。     

Clogging effect of prefabricated horizontal drains in dredged soil by air booster vacuum consolidation

The typical problem that occurs when the conventional vacuum preloading (CVP) method is applied to dredged soil is that the drainage is impeded, permeability is progressively reduced, and clogging occurs in prefabricated horizontal drains (PHDs). This paper proposes a method in which air booster through PHDs under vacuum preloading to reinforce newly dredged soil, and thereby solve the clogging problem. To evaluate the proposed method, several experiments were conducted using soils with variable degrees of consolidation and the effect on clogging determined. Furthermore, the proposed method was compared to the CVP method considering several variables monitored during consolidation and after consolidation. The results indicate that the proposed method is superior to the CVP as it more effectively alleviates the clogging problem. These findings could provide design criteria for dredged soil consolidation in similar projects and for scientific research and engineering practice.     

水泥-水玻璃化学灌浆加固流塑状淤泥的初探

简述淤泥（包括淤泥质土）的工程特性，介绍水泥-水玻璃化学灌浆材料性质，并通过典型的工程实例，充分说明该方法加固淤泥特殊性软土的科学性和可行性，值得进一步推广使用。     

覆水真空预压在福建软土地基处理中的应用

福建某以淤泥质土为主的深厚软土地基处理工程,采用了覆水真空预压的地基处理方法,从真空预压开始到卸除覆水和真空荷载仅用了103天,表层淤泥质土承载力达到85kPa以上。实践证明,覆水真空预压的地基处理方法具有工期短、施工安全、加固效果好、无污染、经济效益明显等优点,值得在福建沿海地区的市政、港口、码头等工程建设中推广应用。