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刚性桩复合地基设计与实测研究 总被引:1,自引:0,他引:1
桩土应力比与沉降是复合地基设计的2个重要参数,针对复合地基设计中难以考虑位移协调的情况,通过对地基基础共同作用方程进行简化,建立考虑桩土位移协调的设计分析方法,并结合广东地区3个不同类型刚性桩复合地基上建筑物在施工期间的沉降与桩土应力监测实例,得到桩土荷载分担以及沉降的变化规律。实测结果表明,所采用的地基承载力和沉降计算方法较好地反映了工程实际状况,比规范方法更加接近实际情况,研究成果可供今后类似工程设计参考。 相似文献
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高速铁路CFG桩筏复合地基沉降特性试验研究 总被引:2,自引:0,他引:2
对京沪高速铁路CFG(Cement Fly-ash Gravel)桩筏复合地基进行了现场试验研究,实测了桩顶、两桩中心、四桩中心处桩间土体的沉降值及路基面沉降值,深入分析了桩顶、两桩中心、四桩中心处桩间土体的沉降及路基面沉降随荷载和固结时间的变化规律,对CFG桩筏复合地基的沉降特性进行深入研究,得到以下主要结论:沉降主要发生在加载期间,即沉降快速发展阶段,期间桩顶、桩间土沉降均占总沉降的60%左右;CFG桩加固区沉降约占相应总沉降的1/4,下卧层沉降约占3/4;路基面沉降曲线成锅形分布,路基中间沉降量较大,路基两侧较小;地基沉降—荷载—时间规律可分为3个阶段,即沉降快速发展阶段、沉降发展阶段和沉降基本稳定阶段;超载预压对于减少工后沉降是必要的,预压3个月后,地基沉降基本上趋于稳定,路堤的预压静置时间应不小于3个月。 相似文献
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CM长短桩复合地基由刚性桩、半刚性桩、天然地基土和褥垫层组成,具有较大的灵活性,可充分发挥桩间土、刚性桩和半刚性桩三者的潜能。理论和实践均表明:CM长短桩复合地基可以有效提高地基承载力,减小建筑物沉降量,降低差异沉降。这种复合地基的设计及应用研究具有很好的理论价值和应用价值。 相似文献
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结合沪宁城际铁路CFG桩网复合地基试验段和京沪高铁砂桩网复合地基昆山试验段,在现场试验断面埋置土压力盒、沉降计和孔隙水压计等监测仪器,获取地基沉降、桩和桩间土压力、孔隙水压等监测数据,对比分析CFG桩与砂桩网在高速铁路地基工作性状及工后沉降控制效果中的差异。分析结果表明:CFG桩网和砂桩网联合堆载预压均可满足高速铁路无砟轨道工后沉降控制要求,CFG桩网复合地基沉降总量与沉降速率均小于砂桩网复合地基,且收敛速度快;受桩刚度差异的影响,CFG桩网复合地基与砂桩网复合地基桩土应力规律存在较大差异,前者桩土应力比随着路堤填筑加载而增大,最终趋于稳定,后者桩土应力比随荷载增加先增大后减小,再增大,呈波浪形变化;CFG桩网地基超孔压消散速率远小于砂桩桩网地基的超孔压消散速率;在施工工期较短的情况下,与砂桩网复合地基相比,CFG桩网复合地基处理技术的工后沉降控制效果更优。 相似文献
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水泥土搅拌桩复合地基沉降计算方法浅析 总被引:2,自引:0,他引:2
1 前言 水泥土搅拌桩是一种介于刚性桩和柔性桩之间的具有一定压缩性的半刚性桩,它与桩间土共同作用的复合地基亦具有一定的压缩性。因此,在复合地基设计时,除应考虑建筑物上部荷载要求外,还应考虑如何控制相对沉降量,即复合地基的变形,使上部结构与地基相协调,避免引起建筑物的沉降过大或不均匀沉降。 复合地基的变形计算方法较多,且其变形与地质条件、上部荷载分布、桩体的设计参数等都有密切关系。现就太原市河西区所进行的较典型的水泥土搅拌桩复合地基施工后建筑物沉降实测值与几种理论计算值之间相比较,以选择接近地区实际的经验 相似文献
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本文针对道路工程中长短组合桩型复合地基变形,通过理论分析和现场试验,研究了深厚软土中长短组合桩复合地基的变形模式及长短组合桩复合地基沉降量计算方法,并且通过试验路段进行验证,为道路工程中长短组合桩复合地基的沉降计算推荐了一种可靠方法. 相似文献
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桥头段刚性桩复合地基现场观测结果分析 总被引:1,自引:1,他引:1
对于深厚软土路基,桥面和路面之间常发生较大的沉降差,产生“桥头跳车”现象。浙江台州浃里陈大桥对低强度桩复合地基处理桥头段软土路基进行了试验研究,并采用变桩长的方式调整桥面和路面的沉降差。采用复合地基使该桥头段的路基沉降减少了2/3,加固效果明显。由于采用了不同的桩长,复合地基沉降沿路堤长度方向分布是均匀的。对现场观测结果进行了分析,包括对路堤下桩顶和桩间土的土压力及沉降和复合地基分层沉降观测结果的分析。 相似文献
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龙口电厂建于山东省可液化的软土层地基上。该软土容许承载力[R]=117kPa。设计要求其容许承载力[R]>245kPa。采用碎石桩加固该软土取得了明显的效果。本文记述了现场试验和建筑物的沉降观测。现场试验包括:①测定振冲器水平振动力作用下产生的地面加速度以及制桩时引起的地面加速度与距振点距离之间的关系;②采用底面积为3.2m×3.2m的大型载荷试验和底面积为0.25m~2、0.5m~2的小压板载荷试验;③测定地基土在制桩前后的标准贯入击数和比贯入阻力的变化,用跨孔法测动力参数的变化;④设置碎石桩前后超孔隙水压力的变化;⑤地面标高的变化。目前建筑物的最大沉降量为40mm。 相似文献
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Single fluid jet-grout strength and deformation properties 总被引:2,自引:0,他引:2
S. Coulter C.D. Martin 《Tunnelling and Underground Space Technology incorporating Trenchless Technology Research》2006,21(6):690-695
The use of sub-horizontal jet-grout columns in the construction of soft ground tunnels is a popular method to provide excavation support. The sequential installation of jet-grout columns in a tunneling environment will result in the jet-grout columns being loaded in a staged manner, resulting in the jet-grout material properties and installation order affecting the magnitude and distribution of surface settlements and face deformations. A laboratory program was carried out to quantify the short-term (<24 h) development of strength and stiffness of a grout with a composition similar to that found in the construction of jet-grout columns. The laboratory tests were conducted at 8 °C to simulate the ground temperatures. Also the laboratory test cylinders were insulated to simulate the boundary condition differences between 600-mm-diameter jet-grout columns in soil and the 76-mm-diameter laboratory samples. 相似文献
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依托穗莞深城际轨道太平隧道工程,在其侧穿一多层房屋时,采用控制地层损失与旋喷桩加固土体相结合的方式,很好地保护了现有房屋的安全与正常使用状态。通过分析隧道穿越过程中房屋的实测变形规律,并进行有限元数值分析,比较了有无旋喷桩和地层损失率对土体垂直位移、房屋角点沉降、房屋整体倾斜、土体深层水平位移的变化规律。分析结果表明,设置旋喷桩和控制地层损失均能有效减小沉降和土体位移,但控制地层损失的效果远比设置旋喷桩要明显。随着地层损失的增大,土体水平位移曲线由“勺”型渐变至S型,最大水平位移位置逐渐上移且位于隧道的上边界附近。 相似文献
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Experimental behaviour of thin-walled hollow structural steel (HSS) columns filled with self-consolidating concrete (SCC) 总被引:1,自引:0,他引:1
In modern building construction, thin-walled hollow structural steel (HSS) sections are often filled with concrete to form a composite column. In recent years, the use of self-consolidating concrete (SCC), or self-compacting concrete, in such kinds of columns has been of interest to many structural engineers. Due to its rheological properties, the disadvantage of vibration can be eliminated while still obtaining good consolidation. Apart from reliability and constructability, advantages such as elimination of noise in processing plants, and the reduction of construction time and labor cost can be achieved. It is expected that SCC will be used in concrete-filled HSS columns in the future because of its good performance. However, the composite members are susceptible to the influence of concrete compaction. The lack of information on the behavior of HSS columns filled with SCC indicates a need for further research in this area.The present study is an attempt to study the possibility of using thin-walled HSS columns filled with SCC. New test data on 38 HSS columns filled with SCC to investigate the influence of concrete compaction methods on the member capacities of the composite columns are reported. The specimen tests allowed for the different conditions likely to arise in the manufacture of concrete: cured, well compacted with a poker vibrator, well compacted by hand, and self-consolidating without any vibration. The main parameters varied in the tests are: (1) column section type, circular and square; (2) tube diameter (or depth) to thickness ratio, from 33 to 67; and (3) load eccentricity ratio (e/r), from 0 to 0.3 mm. Comparisons are made with predicted column strengths using the existing codes such as AISC-LRFD-1999, AIJ-1997, BS5400-1979, EC4-1994, DL5085/T-1999 and GJB4142-2000. 相似文献
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某综合楼的桩基础采用冲孔灌注桩,但该场区岩溶较发育,通过对溶洞的大小、形状及漏浆的严重性进行分析,分别采取不同的施工措施及方案,顺利完成桩基础施工,并取得了较好的技术、经济和质量效果。 相似文献
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Sparsha Sinduri Nagula Duc Michael Nguyen Jürgen Grabe 《Geotextiles and Geomembranes》2018,46(6):790-800
If the bearing capacity of the soil is not sufficient an improvement method has to be considered. In case of soft and cohesive soils the vibroreplacement technique can be used. This paper describes the numerical simulation of a group of encased granular columns under an embankment based on a real life project situated to the north of Hamburg, Germany. The soft soil creep model and the hardening soil model were used to model the behaviour of the soft clay and granular material respectively. The material parameters were determined based on laboratory tests conducted on test samples from the field. The installation effect of columns in numerically modelled based on the cavity expansion method in a 2D axis symmetric model. The results of the installation effect in terms of stress state changes in the soft soil after complete consolidation are then imported to the 3D model involving group of columns. The results of the numerical simulations are validated against field measurement data in form of vertical settlement of the ground at various locations with respect to time and horizontal deformations in the encased columns with depth. 相似文献
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The paper presents the basic parameters and the energy flows of a ground source heat pump system (GSHP) used for air conditioning the New City Hall of Pylaia (Thessaloniki area—Northern Greece). The building is a typical public one, with an air-conditioned area of 1350 m2. The ground source heat pump installation is the largest in Greece, and its operation is monitored with the aid of a DAQ system. The energy flows presented in the paper are based on DAQ recordings of the first 3 years of system's operation. It is proved that the energy demand of the system is significantly lower, compared to that of conventional heating and cooling systems. The seasonal COP of the system has not yet been stabilized, gradually increasing, as it is expected due to the operation of the ground heat exchanger. 相似文献
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A. Michopoulos 《Energy and Buildings》2009,41(9):937-941
A new tool, suitable for energy analysis of vertical ground source heat pump systems, is presented. The tool is based on analytical equations describing the heat exchanged with the ground, developed in Matlab® environment. The time step of the simulation can be freely chosen by the user (e.g. 1, 2 h etc.) and the calculation time required is very short. The heating and cooling loads of the building, at the afore mentioned time step, are needed as input, along with the thermophysical properties of the soil and of the ground heat exchanger, the operation characteristic curves of the system's heat pumps and the basic ground source heat exchanger dimensions. The results include the electricity consumption of the system and the heat absorbed from or rejected to the ground. The efficiency of the tool is verified through comparison with actual electricity consumption data collected from an existing large scale ground coupled heat pump installation over a three-year period. 相似文献