真空—堆载联合预压处理公路软基试验研究

【作者】 邓翔；

【导师】 王星华；

【作者基本信息】 中南大学 ， 建筑与土木工程， 2009， 硕士

【摘要】 随着高等级公路建设的发展,其工后沉降要求越来越高,这使得地基处理技术面临新的挑战。真空-堆载联合预压与传统的以固结排水为主的等(超)载预压和粉喷桩处理软基相比,具有加固效果明显、经济效益显著等特点。本文主要对真空-堆载联合预压处理软基的性状进行系统的探讨。本文以湖南境内常张高速公路高等级路堤试验段为依托,围绕对沉降、尤其工后沉降的控制技术,从设计、施工、测试及沉降估算等方面对该技术处理软基的性状进行了系统研究,得到了下列有益于工程研究和应用的结论：(1)该技术处理软基,施工期间沉降及沉降速率大,有利于工后沉降的控制。(2)以沉降作为控制设计参数,并对路基稳定性进行验算,是合理的设计思想。(3)排水板施工质量的控制和确保必须的真空压力是该技术处理软基施工工艺的关键。(4)测试分析：孔压计一孔多测头埋设技术是可行的,分层沉降测试和管口标高应同时进行：获取了真空度沿深度的传递规律与地表沉降速率随抽真空和堆载的变化规律；探讨了软土层厚度与沉降及其速率的关系,真空—堆载联合作用的影响深度。(5)真空—堆载联合预压处理软基的沉降计算中,荷载处理方法明显影响计算结果,两种荷载分别计算沉降再叠加获取的沉降值大于先叠加荷载获取的沉降值。两种方法共同结论是：e-p法计算结果最小,Es法计算结果次之,e-lgP法计算结果最大。具体方法的选择与软土层厚度有关。更多还原

【Abstract】 With the development of highway, it is more and more difficulty to meet requirements of the residual settlement. Thus, ground improvement techniques are facing many new challenges.Compared with conventional methods (i.e. DCM and equal-loading (or over-loading) pre-compression), vacuum-heaped load combining preloading technique has many advantages, such as improvement the stability of embankment during the construction periods, settlement and its rate, and other performance.In order to study the performance of vacuum-heaped load combining preloading technique on soft soil foundation systematically, a certain trial embankment with its soil foundation improved were constructed, and many testing items were carried out to research control-technology of settlement and residual settlement. Therefore, many valuable conclusions were drawn as following from designing, construction, testing and settlement estimating.(1)The settlement and its rate of soft foundation improved by this technology are remarkable during construction, which is beneficial to control residual settlement.(2)It is reasonable to select settlement as the design parameter, and verify the stability of embankment at any time during the construction periods.(3)It is very important to control strictly construction quality and guarantee essential vacuum pressure.(4)From test and analysis:The method of put more than one piezometer in one bore is practicable. And when surveying settlement of each layer, the waterlevel should be measured at the same time. The distribution law of vacuum degree along with depth and the surface settlement’s rate along with versus vacuum and heaped loads have been obtained. The relationship between soft soil layer’s thickness and settlement, so as its rate were studied, the depth affected by vacuum-heaped loads is also researched.(5)When calculating settlement, the result is influenced obviously by the way of selection loads. The sum of settlement values calculated separately through vacuum loads and heaped loads is bigger than the value caused by total loads. The common conclusion of two ways mentioned above is:The value calculated by e-p method is smallest, by e-lgp method is biggest, and by Es method is in the middle of the two methods above. Which method should be used is related to the thickness of soft soil layers.更多还原