真空-堆载联合预压法在软基加固中的应用

根据太沙基有效应力原理,分析了真空预压和堆载预压加固软基的基本原理。通过现场试验观测和理论分析,认为真空-堆载联合预压法适用于深厚软基的加固处理。     

真空—截载联合预压法在软基加固中的应用

根据太沙基有效应力原理,分析了真空预压和堆载预压加固软基的基本原理,通过现场试验观测和理论分析,认为真空－堆载联合预压法适用于深厚软基的加固处理。     

真空-复水联合预压法在大面积软土地基上的应用

结合在苏州吴越岭秀软基处理工程中的应用，研究了真空一复水联合预压法的加固机理和效果，并与真空预压法和堆载预压法进行了比较。研究结果表明，该加固方法在提高超软大面积地基承载力方面是行之有效的。     

真空堆载预压法控制高速公路软土地基沉降的现场监测试验分析

真空堆载预压法具有真空预压和堆载预压双重加固效果,真空预压产生的侧向收缩变形与堆载产生的侧向挤出变形相抵消,保证了上部路堤的稳定性,加速地基土的固结,提高了施工速度.依托高速公路软基处理实体工程,设置四个现场监测试验段,对完整有效的观测断面的沉降进行了全程监测.分析结果表明,真空堆载预压法加固的路基沉降量主要发生在初期和中期,沉降速率在监测初期较大、中期时达到最大值,后期的沉降量和沉降速率减小,最后阶段最大沉降速率为0.09 cm/d,小于堆载预压规定的允许值1cm/d的要求,表明真空堆载预压法加固效果显著.     

真空联合堆载预压法作用机理及其应用

沿海地区海相沉积的软土地基加固以排水固结为主要方法,但随着工程要求的提高,加固方法也不断发展经体的综合讨论了真空联合堆载预压法的基本原理,加固特点与效果,该法利用真空预压法与堆载预压法加固效果可以叠加的原理,在超软基上可以获得较真空预压法更大的预压荷重,获得更佳的加固效果,同时结合一些工程应用实例具体分析了真空联合堆载预压法的应用效果与发展前景。     

浙江平廊公路工程真空预压软基处理工程实录

介绍了公路软基处理真空堆载预压法设计与施工的实例。通过沉降观测数据,固结度计算,达到了加固目的。     

真空联合堆载预压在加固软土路基中的应用

真空联合堆载预压方法已广泛应用于处理高等级公路的软土地基,与常规的堆载预压法对比,该方法能有效地降低工后沉降,节约工期,并能保证路基的稳定性。通过工程实例,阐述了真空联合堆载方法的加固机理,并通过对现场监测资料的分析,说明该方法用于加固软土路基所取得的良好效果。     

真空联合堆载预压法处理深厚软土试验研究

针对珠海地区的深厚软基,采用真空联合堆载预压法进行加固处理。在施工过程中对软基的地表沉降、膜下真空度、孔隙水压力、深层水平位移等进行监测,得到了真空预压加固软土地基的随时间变化曲线。软基处理完成后对原状土进行原位十字板剪切试验和载荷试验,并取土进行室内土工试验。监测和检测试验分析表明:加固后土的物理力学性质有了明显提高,地基加固效果较好,其影响深度达到25～30 m,在15～20 m范围内加固效果最为显著;但真空预压并未改变软土的触变性,加固后的软土仍应避免扰动。     

真空堆载联合预压加固软土地基效果分析

以苏州某软土地基采用真空堆载联合预压法加固处理为实例,通过现场地表沉降、分层沉降及孔隙水压力监测和室内土工试验等方法,探讨了预压前后软土地基的物理力学性质变化规律,分析了这一处理方法的加固机理和有效性。试验结果显示:预压后土体含水量降低,干密度增大,液性指数减小,压缩模量增大;土抗剪强度指标c、φ值均有提高,特别是土的内摩擦角φ值显著增大。总体来说软土的工程性质得到显著改善,说明真空堆载联合预压法处理软土地基效果显著。     

真空-堆载联合预压法应用试验研究

对杭金衢高速公路真空-堆载联合预压工程,进行了现场试验和资料分析研究。研究表明真空预压能使地基产生较大的沉降速率,同时产生向内的水平位移,从而使真空一堆载联合预压比超载预压具有更强的抗失稳能力,侧向位移量和位移速率与荷载大小有明显的相关性。真空预压的加固深度主要是竖向排水体范围内,而真空-堆载联合预压法的加固深度则可根据堆载的附加应力比来确定。     

湖泊相软土真空堆载联合预压法的离心机试验研究

依托高速公路试验段真空堆载联合预压加固软土路基的现场试验,根据实际路基情况建立离心模型,对真空堆载联合预压加固湖泊相软土地基进行离心机试验,分析了在真空预压和堆载预压联合作用下软土路基的沉降规律,并将试验结果与现场监测结果进行对比,研究了两者沉降的关系。通过对比分析可知,采用真空堆载联合预压加固湖泊相软土路基,地基土在工期内的沉降占总沉降87%以上,加固效果明显;用该方法加固后软基的工后沉降发展缓慢,两年内工后沉降最多为2.5 cm,路堤断面沉降差不超过5 mm,不会影响公路正常使用;试验结果与现场实测值沉降趋势基本相同,但由于现场试验条件及离心试验误差影响,导致两者沉降值存在差异。     

劈裂真空法加固软土地基的效果分析

针对常规真空预压法加固软土地基中存在的问题,介绍了最新研制开发的气压劈裂真空预压法及其施工工艺,并通过现场试验段测试结果分析了劈裂真空法加固软土地基的效果。测试结果表明,较常规真空预压法而言,劈裂真空法可以提高真空荷载向深层土体中的传递效率和加速超静孔隙水压力的消散,既可改善深层软土的加固效果又可加速地基固结,缩短工程工期;劈裂真空法加固地基的沉降效率大于常规真空预压法处理地基,沉降易于收敛,有利于工后沉降的控制。通过加固前后孔压静力触探试验测试结果对比和取样室内试验土性参数变化分析,论证了劈裂真空法加固深层软土地基的有效性和优越性。     

Fracture grouting and geonails for soft soil tunnelling

To stabilise the tunnel faces and slopes in soft clay for the Airport Link construction in Australia, fracture grouting and glass fibre-reinforced plastic (GFRP) soil nails are proposed for the soil improvement as well as ease of handling. The compensation caused by the fracture grouting and the gain in strength due to consolidation as well as the geonail have stabilised the soft clay during construction. Only a small amount of ground settlement during soft clay box-jacking operation is generated so that the railway traffic above the embankment can be maintained without interference. The design method of the fracture grouting ground improvement study for this difficult project is discussed in this paper. Extensive laboratory and field tests were employed to verify the design assumptions and to fine-tune the ground improvement studies. The success of this project in poor ground conditions results from combined efforts of extensive field tests, an improved ground improvement design method and a realistic numerical analysis to assess the unstable/highly stressed zones for the placement of soil reinforcement.     

Bearing capacity and settlement of concrete-cored DCM pile in soft ground

A new kind of composite pile named Concrete-cored DCM (Deep-Cement-Mixing) pile is introduced for supporting medium loads in soft clay ground. This composite pile is composed of an inner precast concrete pile and an external DCM pile socket, where the high strength concrete pile is designed to bear the load of building, and DCM pile socket acts to transfer axial force into the surrounding soils by skin frictions. In this paper we introduce its application in soft ground, and tentatively investigated its bearing capacity and settlement using static loading tests and Finite Element Method. Our study indicates that concrete-cored DCM pile acts as a friction pile and is an economical and effective method for settlement control and capacity improvement in soft clay ground. This study is also valuable for research on the mechanism of other composite piles. This revised version was published online in July 2006 with corrections to the Cover Date.     

越南金瓯化肥项目真空预压监测成果分析

越南金瓯化肥项目软基采用真空预压法处理,在预压过程中采用了膜下真空度、地面沉降、分层沉降、地下水位、孔隙水压力、深层水平位移等多种监测方法。对监测目的、方法做了介绍,根据监测的数据预测了最终沉降,计算了固结度,为卸载提供了依据。     

高速铁路软土地基处理方法对比试验

为探索高速铁路较薄软土地基的加固处理方法,在中国江苏省某铁路试验段进行了针对淤泥质黏土厚度为2～5 m的软土地基现场填筑试验,包括袋装砂井加爆炸、塑料排水板加等载预压、两种间距粉喷桩及砂垫层处理共5个区段。通过为期14个月的原位测试,得到较薄软土地基的沉降变形特性;并通过加固方案效果对比,研究了工后沉降控制效果和工程经济性,其成果对高速铁路软土地基加固处理方案、设计参数的选有一定的参考价值。     

基于孔压静力触探测试的改进分层总和法在软基沉降预测中的应用研究

分层总和法在高速公路软基沉降的预测中得到了广泛的应用。然而,由于基于钻探的土层划分往往比较粗糙以及基于室内试验的压缩模量确定不太可靠,导致沉降预测与实际偏差较大。孔压静力触探（CPTU）作为一种新型的多功能原位测试技术,可以同时测试得到锥尖阻力、侧壁摩阻力和孔压沿深度的连续剖面,较好地改善这一状况。以连盐高速公路为研究实例,采用多变量统计分析中的最优分割理论,基于CPTU高精度测试数据对土层进行了精细划分,并通过实际沉降观测资料的反演分析确定了基于CPTU的压缩模量计算方法,进而通过对高速公路实测沉降和CPTU预测沉降的比较,验证了文中计算方法的有效性     

真空作用面位置对加固效果影响的试验研究

工程中应用广泛的真空预压法和真空-堆载联合预压法主要是指真空作用面位于地表面,通过从上部抽真空实现预压的目的,但对于吹填造陆工程,则不十分合理。通过室内试验模拟上位抽真空和下位抽真空,分别从土体的物理力学性质、沉降量、排水量等几个方面对2种预压方法的加固效果进行了比较分析,阐述了真空作用面位置对加固效果的影响。试验结果表明：下位抽真空的加固效果优于上位抽真空。     

某试验区吹填软基处理工程监测数据分析

结合真空预压法处理大铲湾港区一期工程闸口吹填软土地基工程中的监测数据,通过理论分析对真空预压法加固软基过程中地表沉降、真空度、孔隙水压力等的变化规律进行深入分析研究,其结论具有重要意义。     

Consolidation behavior of a soft mud treated with small cement content

Soft mud can be found in many large size reclaimed lands. Such soils present extremely high settlement potential that needs to be alleviated by means of effective ground improvement techniques. Current knowledge on applying small cement content to reduce settlement potential of soft mud is limited. This study concerns the consolidation behavior and settlement potential of soft mud treated with small cement content. Based on the pH values of soft mud–cement mixtures, oedometer specimens with cement content of 6% were prepared for consolidation tests. The test results show that preconsolidation pressure is rapidly developed and secondary compression is reduced. The ratio of secondary compression index to compression index is also reduced, indicating a change in grain size characteristics. The coefficient of consolidation is increased for consolidation pressures smaller than the preconsolidation pressure. This indicates that treating the soft mud with a small cement content can be very effective for reducing settlements in cases where new loads are small to medium and the time for ground improvement is limited.