【作者】 苗强强；

【导师】 米海珍；

【作者基本信息】 兰州理工大学 ， 岩土工程， 2007， 硕士

【摘要】 对挤密桩间土的挤密效果研究，大多都是定性研究，具体到量化研究还不多。本文在前人研究的基础上，主要做了以下几个方面的工作：首先完成了8个载荷试验，局部浸水试验，大面积浸水试验和大量的土性试验，总结了其处理效果与规律性。通过不同的桩心距，不同的处理宽度，不同的处理深度，不同桩孔填料，单桩与群桩比较，桩体与桩间、桩周土挤密作用，干压、局部浸水、大面积浸水三阶段载荷试验，外荷湿陷，自重湿陷，外荷与自重共同作用下湿陷等方面的试验内容，从而得出挤密地基在密实度、湿陷性、压缩性、承载力、防水抗渗诸方面的效果与规律。当X≤2.25d（X为桩心距，d为挤密桩的桩径，本课题中d=325mm为常数）时，三桩间土的D＞85％，挤密地基在200kPa压力下浸水不湿陷，土常呈较低的压缩性，甚至呈低压缩性，一般α＜0.2MPa^-1（α为压缩系数），E＞10MPa（E为压缩模量），土随着密实度的增加使压缩性继续降低的趋势变化则比较缓慢。当X≤2.75d时，三桩间土的D≥85％，桩间土D≥80％，可使挤密地基在100kPa压力下浸水不湿陷。其压缩性一般将随着土的密实度的增大而降低的比较显著。当D＜79％和饱水时D＜84％，常呈高压缩性，一般压缩系数大于0.5MPa^-1，压缩模量小于4 MPa，此种土压缩性随着土的密实度减小而增大的趋势变化也比较缓慢。当D≤2d时，桩间土D_p=0.97（D_p平均挤密系数），D_min=0.88(D_min最小挤密系数)时，压缩系数从10～20MPa^-1降低到0.2MPa^-1以下，将天然地基在200kPa压力下12cm以上的沉降量降低到0.4～1.6cm，将不到100kPa的承载力提高到200kPa以上，承载力提高了一倍以上。当X＜2.5d、D_p＞0.87、D_min≥0.82时，处在基本单元重心附近，局部出现天然湿度下压缩系数在0.2～0.3MPa^-1范围，饱水状态下压缩系数在0.4～1MPa^-1的区域，大部分天然湿度下压缩系数小于0.2MPa^-1，饱水时压缩系数小于0.4MPa^-1，挤密地基在200kPa压力下沉降不超过2cm，承载力将提高到150～200kPa，比天然地基增加50～100％。当X＜2.25d，土的D＞87％或e＜0.89（e为孔隙比）时，一般具有较小的透水性。当D＞94％或e＜0.7时，常成为不透水性的土，至少为轻微的透水性土。在挤密地基中，充分挤密区和有效挤密区的“Ⅰ亚区”，往往属于不透水性或透水性很小的土。更多还原

【Abstract】 There is still few analysis and study about the compaction effect to quanlity characteristic ,most of them are definition study. In the thesis ,on the basic of other people achievement we carry out study from those angles:We have completed 8 experimental study of loadings, partial inundating test, large area inundating test and great deal of test of soil characteristic. We summarized their effect and rule from improvement foundation. Through different centre distance of pole ,differen improvement width, depth and different filled soils ,comparing to one pile and more piles, pile themselves and pile between, and pile surrounding compaction soii affecting, natural condition compressing ,partial inundating, large area inundating three phase tests, exterinal loading collapsibility, themselves gravity collapsible external loading and gravity commonly affecting tests. We can conclude the affect and rule from compacting foundation in density degree,collapsible compress, bearing capacity ,precluding water and preventing filter and precluding water ect.When（?）ry unit weight of soil were more than 85% of the maximum,coefficient of collapsibility less than 0.015,initial pressure of collapsibility no less than 200kPa.Wh（?）ry unit weight of soil more than 80% of the maximum,in the 100kPa pressure,coefficient of collapsibility usually less than 0.015,initial pressure of collapsibility also more than 100kPa.When centre distance of piles were less than 2.25d,average dry unit weight of three pile soils usually close or more than 85% of the maximum , on this condition compacting ground will not collapse in the 200kPa pressure and inundating .When centre distance of piles were less than 2.75d,average dry unit weight of three pile soils usually close or more than 80%, compacting ground will not collapse in the 100kPa pressure and inundating.When damp of soil is suitable ,its dry unit weight of soil close or more than 84% of the maximum and dry unit weight of saturation soil close or more than 88% of the maximum ,under this conditions ,soil usually represent lower compressibility. coefficient of compressibility usually less than 0.2MPa^-1,compression modulus more than 10MPa,this soil with compaction degree increase, the trend of compress decline keep a stable phase.When dry unit weight less than 79% of the maximum and dry unit weight of saturation soil less than 84% of the maximum soil usually represent higher compressibility.Coefficient of compressibility usually more than 0.5MPa^-1, compressibility modulus less than 4MPa,this soil compressibilityincrease change is very slowly ,with the compaction decline.Between two condition soil ,its compressibility change greatly ,with the compaction increasing ,the trend of compressibility evidently decreasing.When centre distance of piles less than 2d,average compaction coefficient more than 0.97,minimum compaction coefficient more than 0.88,all of point soil of piles in any damp,compressing coefficient from 10～20MPa^-1 to lower than 0.2 MPa^-1.Settlement quantity of nature ground from 12cm to 0.4～1.6cm in the 200kPa pressure ,pressure ground bearing capacity increasing 2 times from 100kPa to 200kPa .Centre distance of pile less than 2.5d ,average compaction coefficient more than 0.87,minimum compaction coefficient more than 0.82 ,in the near of heartbeat of basic monad,most of compressing coefficient in the nature damp less than 0.2MPa^-1,in the saturation less than 0.4MPa^-1,besides partial in the nature damp range from 0.2 MPa^-1 to 0.4MPa^-1 ,in the saturation between 0.4MPa^-1 and 1MPa^-1.Settlement of compaction ground less than 2cm.Bearing capacity will improve to 150 200kPa,compared to nature ground increase by 50～100%.When centre distance of pile less than 2.25d,dry unit weight of soil more than 87% of the maximum or void ratio less than 0.89,water hardly have permeability through soil .When dry unit weight of soil more than 94% of the maximum or void ratio less than 0.7,it become no permeability water,in the compaction ground ,fully compacting region and I district of effective compacting region were hardly or cann’t permeability water.更多还原