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劈裂注浆抬升既有管道效果分析及工程应用 总被引：1，自引：0，他引：1
地铁车站施工中常穿越大量的市政管道,由于隧道开挖引起地层损失和地表沉降,地下管道将会发生变形,往往影响地铁施工,注浆是对地下管道进行沉降控制的主要技术措施。以北京地铁黄庄站下穿热力管道抬升注浆工程为研究对象,利用三维有限差分数值方法分析了新建车站开挖引起超大管道的变形特征。结果表明,在抬升区注浆单元施加膨胀压力可以较好模拟注浆抬升既有管道的效果;采用应变软化模型,可以有效模拟土体材料的弹塑性力学行为,反映注浆完成后浆脉的固结和周围土体的湿陷作用。对比注浆抬升模拟计算和沉降监测结果,验证了有限差分数值方法模拟劈裂注浆抬升管道过程的正确性和有效性。同时模拟分析注浆抬升管道的影响因素,获得了一些规律性的认识,为劈裂注浆抬升地下管道工程的施工和设计提供指导。 相似文献
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为研究管幕法群管顶进施工过程中地表位移变化规律,依托上海田林路下穿中环隧道工程,对地表位移实测数据进行了详细分析。通过数据处理发现,管幕施工期间变形发展可细分为7个阶段,其中包括4个推进阶段、3个暂停推进阶段。管幕推进阶段的地表位移由地层损失沉降和注浆引起的地表隆起叠加而成;暂停推进阶段的地表沉降主要是固结沉降。运用Peck公式对地表位移进行描述,通过现场数据反分析出各根钢管推进时的沉降槽宽度系数i和地层损失率η。基于分析结果,提出了适用于上海软黏土的i和η 计算公式,其中i的公式只与钢管半径R、钢管埋深h和土体内摩擦角φ 有关,而η的公式表达成随时间的双曲线函数。注浆导致的地表隆起可分解成各根钢管顶进伴随注浆造成的负地层损失。运用上述方法对地表位移进行预测,并与实测结果对比,验证了文中方法的正确性,成果可对类似管幕法工程施工引起的地表位移预测提供科学参考。 相似文献
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土钉墙在超软地基基坑支护中的应用 总被引：9，自引：2，他引：7
在论述宁波市区软弱地基特征及基坑支护结构现状的基础上,分析了采用土钉墙支护结构支护深度6.0 ~7.0 m软弱基坑的可行性。在镇海炼化工程的超软弱地基中,用土钉墙来支护深度为6.0 m的基坑,并获得成功,开辟了用土钉墙支护宁波软弱基坑的先例。由于宁波软弱地基的特殊性,应对土钉墙实施过程中可能出现的问题进行预测和预防。详细地介绍了土钉墙设计施工的经验和教训,并提出了适用于宁波软土基坑的土钉墙基坑支护型式。由于土钉墙基坑支护结构的经济合理性,可以在宁波市区的基坑支护中推广应用。 相似文献
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Myint Win Bo Ming-Fang Chang A. Arulrajah Victor Choa 《Geotechnical and Geological Engineering》2012,30(1):45-62
Geotechnical ground investigation is important in all construction works particularly, land reclamation projects. The Changi
East reclamation project is a mega project that involves creation of land space as large as 3,000 hectares in multiple phases
between 1991 and 2005. Ground investigation plays a critical role in the Changi project which involved substantial amount
of ground improvement works after reclamation by sand filling. One important aspect of the investigation was to evaluate the
geotechnical characteristics of the underlying compressible soils beneath the original seabed for the selection of suitable
methods of ground improvement. The other important aspect of the investigation was to characterize and verify the compactness
of the reclaimed sand fill. Many types of in situ tests were extensively used in the project. The field vane shear test provides
correlations between the undrained shear strength and depth for the upper and the lower marine clay strata in the Northern
part and the Southern Part of the reclaimed site. Combined with laboratory undrained shear strength tests, the field vane
strength profiles allow the derivation of the undrained shear strength over effective stress ratios for the upper and the
lower marine clays. In addition, results from three other in situ tests, the piezocone cone penetration test, the flat dilatometer
test, and the self boring pressuremeter test provided useful verification of these correlations. A field-performance based
method of assessing degree of consolidation in the underlying clay was developed by combining field monitoring, laboratory
testing and conventional as well as specialized in situ testing. An effective use of in situ testing methods for assessment,
the outcome of ground improvement and for fill quality control in the densification of granular soils is illustrated with
field observation data collected at the project site. 相似文献
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劈裂真空法加固软土地基的效果分析 总被引：1，自引：0，他引：1
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。 相似文献
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In-situ testing of Singapore marine clay at Changi 总被引：2，自引：0，他引：2
The Changi East Reclamation Project in the Republic of Singapore comprises of the ground improvement of marine clay with the installation of prefabricated vertical drains and subsequent surcharge placement. Prior to the commencement of land reclamation works, a series of in-situ tests were conducted in marine conditions with the use of various in-situ testing equipment. The In-Situ Testing Site was located in the Northern area of the project where the thickest compressible marine clay layers existed. The in-situ tests carried out were with the field vane, piezocone, flat dilatometer, self-boring pressuremeter and BAT permeameter. In-situ tests were conducted to determine the undrained shear strength and overconsolidation ratio of the marine clay. In-situ dissipation tests provide a means of evaluating the in-situ coefficient of horizontal consolidation and horizontal hydraulic conductivity of soft soil and were used to estimate these properties of Singapore marine clay at Changi. 相似文献
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低能量强夯法加固粉质黏土地基试验研究 总被引：5，自引：1，他引：4
结合上海某铁路集装箱中心站地基处理工程,针对其场区上部粉质黏土、下部砂质粉土的地基条件,对低能量强夯法加固此类地基的适用性进行了现场试验研究。通过对夯击过程中超静孔隙水压力随夯击次数、深度、距离的变化规律及在不同性质土层中的增长与消散规律的研究,提出了运用试验手段确定强夯夯击次数、夯点间距、有效加固深度及两遍强夯间隔时间等施工参数的方法。同时,用静力触探试验和标准贯入试验对地基加固的效果进行了检验,结果说明低能量强夯法加固粉质黏土地基的适用性,从而进一步拓宽了低能量强夯法的应用范围。 相似文献
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盾构隧道实测土压力分布规律及影响因素研究 总被引：1，自引：0，他引：1
以大量现场实测土压力为基础,分析了影响盾构隧道衬砌土压力的一些主要因素,总结出不同地层地铁盾构隧道长期稳定土压力的分布规律,并探讨了盾构施工期土压力随时空的变化情况。研究得出,地下水位高低对稳定土压力大小及分布影响较大;作用在管片上的长期土压力大小与地层衬砌刚度系数有关,当地层衬砌刚度系数为1.5时,管片竖向及水平土压力都较小;盾构施工期临时荷载对管片土压力影响不可忽视,无论是黏土地层还是砂土地层,大的注浆压力及注浆率将导致作用在管片上的稳定土压力分布不均;管片土压力可按时空分为4个阶段,拼装阶段、同步注浆阶段、浆液凝固阶段及后期稳定阶段,其中同步注浆阶段管片周边最大土压力为稳定阶段的2～3倍。 相似文献
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软土地基注浆扩散过程数值模拟研究 总被引：1，自引：0，他引：1
廊沧高速公路K132+177～K132+258软土地基主要由低液限中、高压缩性黏土层组成,属于滨海沉积类型,采用静力注浆方法进行了加固处理,并在现场分别对全孔一次性和自上而下分段式注浆施工方式进行了试验及室内研究。基于该路段软土地基地基物理力学性质和注浆试验地表变形观测资料,利用FLAC3D软件对该软土地基在不同注浆方式（全孔一次性注浆、自上而下分段式注浆）和在0.5、1.0 、2.0 MPa注浆压力作用下浆液在土层中的扩散过程进行了分析。其结果表明,在相同注浆压力作用下,自上而下分段式注浆效果比全孔一次性注浆效果好,而注浆压力的增大对浆液在土层中的扩散是有利的,但压力过大会导致地面冒浆,应根据现场实际情况选择合理的注浆压力 相似文献
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In situ dissipation tests provide a means of evaluating the in situ coefficient of horizontal consolidation and horizontal
hydraulic conductivity of soft clays. Dissipation tests by means of piezocone (CPTU), dilatometer (DMT), self-boring pressuremeter
(SBPT) and BAT permeameter (BAT) were utilized in the characterization of the coefficient of horizontal consolidation and
horizontal hydraulic conductivity of Singapore marine clay at Changi in a land reclamation project. Dissipation tests were
carried out prior to reclamation as well as after ground improvement with vertical drains to compare the changes in the coefficient
of horizontal consolidation and horizontal hydraulic conductivity prior to and after ground improvement. Tests were carried
out in a vertical drain area as well as in an adjacent untreated control area after 23 months of surcharge loading, for comparison
purposes. The purpose of this research is to determine the horizontal consolidation parameters of Singapore marine clay prior
to reclamation as well as after 23 months of surcharge loading with and without vertical drains by means of in situ dissipation
tests. 相似文献
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This paper presents a theoretical model for investigating the installation effect of high pressure jet grouting column in soft clay. The model is formulated by assuming the installation process as a series of pressure-controlled spherical cavity expansion in semi-infinite soil, of which the approximate solutions are derived by combining use of two fundamental solutions of spherical cavity expansion in finite spherical symmetry soil and displacement-controlled spherical cavity expansion in semi-infinite soil. The approximate solutions are then validated by comparing the predictions with FEM results as well as published results. The comparison results show that the presented approximate solutions are suitable for the problem of pressure-controlled spherical cavity expansion in semi-infinite soil, particularly in evaluating the limit expansion pressure as well as the expansion pressure-ground surface displacement relation. Subsequently, the proposed approximately solutions are applied to interpret the limit injection pressure and the grouting pressure-ground surface displacement during the installation process of HPJ-GC. Some parametric studies are also conducted. Furthermore, an instrumented field test study of HPJ-GC is conducted in the thick soft soils comprising quaternary alluvial and marine deposits of the Lianyungang-Yancheng Highway located in Jiangsu Province, China. The measured ground heave is compared with the analytical predictions using the proposed theoretical model. Reasonable agreement is achieved. 相似文献
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The existence of thick compressible varved clayey silt deposits along the Delaware River presents one major obstacle for design and construction of structures or industrial facilities in this region. To understand the characteristics of this thick weak soil layer and then develop reliable soil parameters for future earthwork design and construction, a comprehensive soil testing program was carried out. The program consisted of both in situ tests [e.g., standard penetration test borings, piezocone penetration test (CPT) soundings, Marchetti flat dilatometer test soundings, seismic shear wave test soundings, CPT pore pressure dissipation tests, and field vane shear tests] and laboratory tests (e.g., soil index tests, consolidation tests, triaxial tests, and chemical tests). Additionally, a field surcharge test program with and without installation of wick drains was carried out to investigate the compressibility of the thick clayey silt deposit and the efficiency of wick drains to help accelerate consolidation. The field and laboratory test results showed that the varved clayey silt deposit was normally consolidated to slightly overconsolidated and moderately to highly compressible. Its physical properties were intermediate between those of Savannah muddy clay and Shanghai soft clay, while much closer to that of Shanghai soft clay. Due to its lamination structure in the horizontal direction, the horizontal consolidation coefficient of the varved clayey silts was significantly greater than that in the vertical direction. The measured undrained shear strength of the varved clay silt almost increased linearly with depth. The installation of wick drains in the thick clayey silt deposits accelerated primary consolidation, but showed no effect on the secondary consolidation under constant loading. The findings obtained from this study will be beneficial for future design and construction of earthworks along the Delaware River. 相似文献
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盾构施工与波浪荷载耦合作用后软土力学特性 总被引：1，自引：1，他引：0
针对波浪循环荷载作用和盾构穿越海堤过程中的施工扰动对下卧软黏土地基的弱化效应问题,研究了盾构施工与波浪荷载耦合作用后海洋软土的强度和刚度变化规律。通过逐步降围压的方式模拟盾构施工过程中的地层损失所引起的应力释放,循环加载3 000次模拟波浪荷载长期作用,开展了波浪和盾构施工耦合作用后的软土空心圆柱扭剪不排水剪切单元体试验。试验结果表明:(1) 在盾构施工与波浪荷载耦合作用下,软黏土的强度和刚度均随围压变大而增强,在同一围压下,二者均随波浪循环次数和土体损失率（δ）的增大而减小。(2) 在相同的波浪循环剪切次数下,软黏土初始切线模量随δ的增加而呈线性递减趋势,而软黏土黏聚力和内摩擦角随δ的增加而呈现非线性减小。波浪和盾构施工耦合作用后软黏土的强度和刚度均呈现不同程度的衰减,二者耦合扰动作用对软黏土的弱化效应在实际工程中应充分重视。此研究对探讨复杂扰动条件下海洋结构性软土力学特性规律,丰富和发展扰动状态下结构性软土的计算理论,以及对海岛基础设施建设具有重要的参考价值。 相似文献
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Ahmad Safuan A Rashid Aliff Ridzuan Bunawan Khairun Nissa Mat Said 《Geotechnical and Geological Engineering》2017,35(4):1271-1298
Nowadays, several techniques are employed to improve the problem of carrying out construction in soft soils by increasing the strength of the soil foundation and reducing the settlement of the soil. Among these stabilizing techniques, the deep mixing method is regarded as the most popular. The deep mixing method is a soil modification method where the soil is mixed in situ with stabilizing agents, commonly soil–cement columns. It increases the strength of the soil, providing bearing resistance and improved settlement performance. Deep mixing is carried out in situ using a machine equipped with mixing blades mounted at the end of a tube that has a nozzle at the lower end. The stabilizer agent is injected into the soil via the nozzle using a pumping system so that it mixes with the soil as the blades are rotated. Throughout this paper, previous works by numerous researchers on deep mixing including laboratory work, full-scale field tests, analytical and numerical analyses related to bearing capacity are reviewed. The techniques and results used are discussed with the help of figures depicting charts, failure modes, and the model configuration setup. It was found that the deep mixing method is suitable for use with any type of soil and provides a better alternative to the existing method of improving soft clay ground, especially with regard to the soil bearing capacity. In addition, future research is needed to improve the use of the method for soil improvement in the construction industry. 相似文献
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D. T. BergadoJ. C. ChaiN. Miura 《Computers and Geotechnics》1995,17(4):447-471
The behavior of a reinforced embankment on soft Bangkok clay has been analyzed by plane strain finite element method. The finite element analysis considers the selection of proper soil/reinforcement properties according to the relative displacement pattern of upper and lower interface elements. The large deformation phenomenon is simulated by updating the node coordinates, including those of the embankment elements above the current construction level, which ensures that the applied fill thickness simulates the actual field value. A full scale test reinforced embankment with a vertical face (wall) on Bangkok clay has been analyzed by the proposed finite element method, and the numerical results are compared with the field data. The response of a reinforced embankment on soft ground is principally controlled by the interaction between the reinforced soil mass and soft ground and the interaction between the grid reinforcement and the backfill soil. The tension in reinforcement and lateral displacement of the wall face varied during consolidation of foundation soil. The maximum tension force occurred in the reinforcement layer placed at the base of reinforced mass, due to bending of the reinforced mass resulting from differential settlements. It is considered necessary to account for the permeability variation of the soft ground foundation in the finite element analysis. 相似文献
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人工冻土的物理力学指标是地铁隧道工程冻结壁设计参数和开挖的依据。通过对宁波轨道交通一号线联络通道②～⑤海相沉积软土地层人工冻土的室内单轴抗压强度和抗剪强度试验,获得了冻结前后②～⑤土层的比热容、导热系数、内摩擦角和粘聚力的对比结果以及不同温度条件下冻土的极限抗压强度、弹性模量和泊松比结果。试验结果表明:②～⑤土层人工冻结土的物理力学指标较原状土有很大的提高,人工冻土极限抗压强度、弹性模量随温度的降低而增大,近似呈线性关系。各土层泊松比、温度的变化对冻土泊松比影响较小,随温度的降低有一定的减小。在-10℃条件下,冻结前淤泥质土、粘土层的内摩擦角和粘聚力有了大幅的提高,而③1砂土层的内摩擦角增幅较小。 相似文献