【作者】 杨静；

【导师】 王清；

【作者基本信息】 吉林大学 ， 地质工程， 2009， 博士

【摘要】 随着沿海城市经济的发展和城市基本建设的蓬勃开展,国内一些港口存在着严重的陆域不足现状,将疏浚出来的淤泥用于填海造陆,已成为沿海城市土地开发的重要手段。这种土的特点是含水率大、呈流塑状态、强度低、压缩性高,一般不能满足工程需要。如能将吹填土快速从泥浆状态转变为具有一定承载力的地基,将对填海造陆工程建设带来巨大的效益。边吹填边进行吹填土固结排水的方法为吹填土加固处理提供了新的思路,该方法可以大大提高工程进度、提高经济效益。但是,在吹填土吹填的同时进行加固处理时,由于吹填土处于流塑甚至悬浮状态,土颗粒之间粘聚力较低,在吹填土工程处理过程中,如果排水过程控制缺乏科学性,易造成吹填土结构强度未形成时,土颗粒被高孔隙水压差迁移到排水通道表面,在排水通道表面形成具有一定厚度的泥膜,从而影响排水通道的渗透性,严重地影响了吹填土工程处理质量,大大增加了能耗,提高了工程处理费用,延长了工程处理时间,同时给生产上带来了一定的盲目性和随机性。因此,本文结合国家自然科学基金项目“海积软土地基加固过程中有机质的作用和影响”(No.40372122),对高粘粒含量吹填土加固过程中结构强度的形成进行了模拟试验研究。本文以天津滨海新区高粘粒含量吹填土为研究对象,首先对天津滨海新区高粘粒含量吹填土的粒度成分、矿物成分、易溶盐含量、比表面积等性质进行了分析。其次,采用自制的室内模拟试验装置进行了室内模拟试验——量筒模拟试验和大型试验箱试验。量筒模拟试验包括自重沉降试验和排水试验,通过自重沉降试验得到不同土水比吹填土的沉降量与时间关系曲线,确定不同的静置时间,排水试验中根据自重沉降试验确定的不同静置时间控制吹填土试样静置后排水,通过排水总量与时间关系曲线发现,泥浆静置时间越长,排水量越大。通过大型试验箱试验对不同渗流压力下试样的孔隙水压力、沉降速率和渗流总量进行了研究,并在不同渗流压力下形成稳定结构试样的不同深度处取样,对其微观结构特征进行定性和定量研究,采用分形理论验证试样微观结构的分形特征,探讨了微观结构单元体和孔隙分形维数与渗流压力之间的关系。最后,应用颗粒流理论对不同静置时间试样在不同渗流压力下的渗流情况进行模拟研究,通过试样管壁处孔隙率和渗透系数的变化发现:试样结构强度的形成与静置时间有关,渗流压力不同,所需要形成的结构强度不同,并得到了不同渗流压力作用下使试样稳定渗流所需的结构强度需要静置的时间。本文为高粘粒含量吹填土加固过程中结构强度的形成研究提供了一种新的思路。更多还原

【Abstract】 With the rapid development of economic construction, coast reclamation project has become one of the main measures for resolving the increasing shortage of the land resources of the coastal cities. So, it is a good idea of gaining two advantages by a single move to make full use of dredged silt in sea reclamation. But the grain of dredger fill is fine, with high water content, large void ratio, low penetrability, low strength, high compressibility, can not satisfy the engineering requirement. It is needed a long time to solidify naturally, it can be reinforced after the forming of surface duricrust, and it is influence on project progress. Therefore, how to find a method which can quickly change the serous fluid of dredger fill to foundation with bearing capacity has already been the urgent technological subject.Method which consolidation and drainage during dredger open up a new way for dredger fill reinforcement treatment. This method has advantage of short construction period, without pollution, is reasonable and economical. But, without guiding of scientific, drainage consolidation before dredger fill have not form a structural strength, the thick sludge membrane appeared around the drainage pipes. Then the efficiency of reinforcement is seriously influence. Blindness and randomness brought to production. Therefore, the study of stability structural strength during reinforce dredger fill is necessary. It can provide theory reference for dredger fill reinforcement and service to engineering.So the structural strength of dredger fill in Tianjin Binhai New Area are studied in this paper associated with the project of "study on the influence of organic matter in the progress of marine soft soil foundation consolidation" sponsored by the national natural scientific fund. The study on the form of structural strength of dredger fill with high clay content during consolidation progress is studied on the basis of indoors physical and chemical properties, indoor simulation test, quantitative analysis of microstructure parameters, extracting of microstructure fractal parameters and pfc simulation.Following study is done in the paper: 1. The granularity composition, mineral composition and soluble salt content of dredger fill in Tianjin Binhai New Area were introduced. Dredger fill in Tianjin Binhai New Area naming silt, when added dispersant, it naming light clay, with obviously sham silty soil in silt fraction. Mineral composition mainly is original mineral, subsidiary role is secondary mineral. Dredger fill with the property of moderate plastic, low liquid limit. Soluble salt content mainly is sodium ion and chloride ion. Sedimentary environment belongs to weak alkaline.2. Dredger fill with high clay content of Tianjin Binhai New Area was applied to do a series of indoor simulation experiments, graduated cylinder model test and large-scale apparatus test.①Graduated cylinder model testGraduated cylinder model tests include self-weight consolidation test and drain test. Through self-weight consolidation test find the relationship curve between settlement and time of sample with the quality ratio of soil and water were 1:2.5 and 1:3, and ensure stewing time for drain test. Based on the stewing times, drain test was done after a period of the soil stewing time, and find the relationship curve between water discharge and time, by the curve we found the longer the stewing time, the more the final water discharge.②The large-scale apparatus testThe large-scale apparatus test was to be done. In different circumstances, the settlement, drainage rate and pore water pressure were studied under the different consolidation proceedings. In addition, the basic property of the upper and the lower part of the sample at different stress and at all levels of consolidation were analyzed. Seepage rate and pore water pressure increased with the seepage pressure increases, pore water pressure increased with the distance increases of drainage channel and piezometric tube. Moisture content of the dredger fill was decreased as the seepage pressure increases, and the upper was greater than the lower. The specimen surface area and cation exchange capacity were increased as the seepage pressure increases. The total amount of soluble salt of the upper dredger fill in the large-scale apparatus was more than the lower, and as the seepage pressure increases, the total amount of soluble salt was decreased. The organic content of the upper was higher than the lower part of dredger fill in the large-scale apparatus. With the seepage pressure increases, the value of the sample penetration, bearing capacity and compression modulus were increased, fluid index decreased, the strength increases, the strength of in the lower soil was greater than the upper.3. Through collecting the micro structural of the dredger fill photographs which formed a stable structure under different seepage pressure in large-scale apparatus test. Through qualitative, quantitative and fractal features analysis of microstructure, results show that:①With the seepage pressure increases, the directionality of structural unit and pore increases. The structure changed gradually from the honeycomb-flocculation structure to agglomerated structure, and the contact type among the minerals is from edge to edge connection mainly to the transition to be edge to edge and edge to face connection.②The large interval content of the particle diameter in the lower higher than in the upper. With the seepage pressure increases, the abundance ratio, circularity and mean shape coefficient of the structural unit decreases, the directionality increases.③With the seepage pressure increases, the content of the large pore reduced, the content of the small pore increased, the abundance ratio, circularity and mean shape coefficient of the structural pore decreases, the directionality increases, and mainly concentrated on the 0°-10°.④The morphology, orientation, pore morphology and plane distribution of the sample’s micro-structure units exist the self-similar fractal characteristics when formed stable structure under different seepage pressure.⑤With the seepage pressure increased, the morphology fractal dimension of the microstructure unit particles increased, the content of small unit increased, the complex morphology of the particles is higher, the morphology fractal dimension in the lower less than in the upper. The directional fractal dimension of the structural unit tends to decrease, the directional fractal dimension of the microstructure unit body is between 0.6-0.8.⑥With the seepage pressure increased, the morphology fractal dimension of the microstructure pore increased, the plane distribution fractal dimension of the structural pore tends to decrease, the plane distribution fractal dimension of the microstructure pore is between 0.5-0.7.4. The indoor experiments are numerical simulated with the theory of particle flow code. The samples are under the condition of different seepage pressures and different stewing times. Results conclude the relationship curve between internal porosity and permeability coefficient with time steps. Through the numerical simulation, the flowing conclusions were obtained:①The curve of porosity and permeability to time step fluctuate frequency from more to few, strength from strong to weak, with the stewing times increases. This illustrate that the structural strength of sample increase, and particles harder to recombine.②When seepage pressure is 10KPa and 20KPa, porosity and permeability to time curve tends to be stable at the end in tube wall of the sample standing for 30 days. It means that stable seepage is formed. When seepage pressure is 40KPa and 80KPa, porosity and permeability to time curve tends to be stable at the end in tube wall of the sample standing for 60 days, the stable seepage is formed.③When drainage consolidation under 20KPa seepage pressure, sample need to standing for 30 days. When drainage consolidation under 80KPa seepage pressure, sample need to standing for 60 days.④Sample’s structure strength enhances as standing more days; the larger the seepage pressure, the greater the structure strength is needed to avoid sludge plugging effect of sample.更多还原