【作者】 张中琼；

【导师】 王清；

【作者基本信息】 吉林大学 ， 地质工程， 2009， 硕士

【摘要】 本文在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研究”(40372122)资助下,结合吹填土“三高一低”的特殊工程地质性质,开展吹填土快速加固的室内模拟试验研究。在自然条件下,吹填土存在着固结时间较长、强度增长较慢等方面的问题,不能满足城市建设的要求。这就需要通过工程措施对吹填土进行加固,使其尽快作为土地资源用于城市建设。结合吹填土加固具有阶段性的特点,在较短的时间内获得符合工程要求的吹填地基土,若在吹填过程中就开始加固,与传统加固方法相比可以节约时间,同时获得较好的加固效果。对该方法的研究,为吹填土加固提供一种新的思路。吹填土以结合水连结为主。已有工程实际表明,其自然排水固结时间与粘粒含量密切相关。粘粒含量越高,加固难度越大,加固时间越长。过大压力下吹填土的加固,会在竖向排水体周围形成低渗透性的粘土层,即泥皮。泥皮的形成影响吹填土的加固。为使试验具有代表性,本文以天津滨海新区临港工业区高有机质高粘粒含量吹填土作为试验土样。考虑塑料排水板布设间距,以大面积吹填土加固的一个单元为研究对象。设计1m×1m×1m的试验箱,按照试验要求制备均质、各向同性的试验土样。采用下方排水分阶段加固的方式进行室内模拟试验研究。结合吹填土土结构阶段性形成的特点与外荷载的情况,将试验分为三个试验段:静水沉降、自重排水、真空加压排水阶段,根据加固的阶段性设计试验。吹填土的加固主要是获取其各阶段工程性质变化数据,揭示吹填土的加固机理。基于这一研究目标,在试验过程中,采用原位测试和取样测试相结合的方法,获取试验土样的基本物理性质、化学性质和力学性质。对试验关键试验阶段取代表性的土样,进行土结构变化的研究,以达到试验要求。在试验初始时测试土样的基本物理性质和化学性质。首先,在各个不同的试验阶段获得试验土样的基本工程地质性质参数的变化情况,对其强度增长的情况进行分析。其次,通过在不同试验阶段不同深度不同距离孔隙水压力的消散情况和分层沉降标的变化情况,对加固过程中有效应力的增加情况进行分析。加固土体在不同深度、距竖向排水体不同距离表现出不同的固结特征,分析吹填土加固的影响因素,提出过程控制的概念。再次,在不同排水条件下不同深度吹填土微观结构特征进行定性和定量研究,分析不同加固阶段吹填土固化的微观特征,从微观角度揭示吹填土的固化机理。最后,建立自重排水条件下吹填土加固的渗流模型,并通过室内实测数据对模型进行验证。本文为吹填土加固提供了一种新的方法和思路,为沿海城市用地紧张提供工程措施。更多还原

【Abstract】 This paper were subsidized by the National Natural Science Foundation project "Strengthening of marine soft soil organic matter in the course of the role and impact of research" (40372122). Study the in Lingang Industrial Area Binhai Region Tianjin. Indoor model tests carried out during december 2007 to october 2008. Selected dredger fill which contained more clay and organic matter for testing, preparation of soil samples in accordance with the test requirements, soil samples homogeneous, isotropic, and layer-by-layer filled the test chamber. The beginning of the experiment trial, soil samples of the basic physical properties, chemical properties, material composition, mineral composition being tested. Considered the dredger fill engineering geological characteristics and changes in external load, dredger fill’s reinforement stage will be divided into water and soil separation stage , self-drainage stage, pressurized-drainage water stage . Through the in situ testing, sampling testing, soil micro-structural analysis and other methods to study the changing of dredger fill’s nature of engineering geology , Thinking process control reinforcement was made.In this paper, the following research were worked:First of all, based on the idea of the rapid reinforcement , designed the indoor simulation tests. Rapid reinforcement was in a relatively short time of reinforcement to obtain better results. Reinforcement effect Reflected mainly in two aspects :the reinforcement of time ,distance from the drainage body strength of the growth of intensity at different distances of the drainage body. Under side drainage method be used in experiment, selected a reinforcement unit for the study in dredger fill reinforcement field,and considered the case which the drainage board arrangement situation in reinforcement methods of drainage, so Research unit was 1×1×1m. the process of intensity growth was the process of soil structure formation constantly, and effective stress increasing process . Pore water pressure change and reinforcement of the settlement of soil were the important data which were used to evaluate the effect of reinforcing, Pore water pressure monitoring, tiered settlement monitoring, displacement monitoring data being monitored in the test phase, at the same time, testing the changements of the fundamental nature of soil which were used to determine the engineering nature of dredger fill in all test phase. Therefore, undisturbed soil samples taken to test the fundamental nature in some times of the continuous monitoring of the representation of time in the reinforced soil. To prepare for explain reinforcement mechanism of low- drainage.Second, hydraulic fill mud was a dispersed systems, soil particles for the solute and water as the solvent. The solution was very unstable,Emergence of solid-liquid slurry differentiation process was the separation of water and soil process. The process of separation of water and soil have closely relationship with material composition, particle size composition, moisture content and so on. The shorter time of the separation of water and soil and the lower moisture content, the more fine-grained content, the more time of separation of water and soil required. The formation of the initial structure of soil longer. After the initial structure of soil formation, the soil will have the ability to resist external pressure, To start the drainage, so as to shorten the time of reinforcement. Fill in the large-scale, they can fill edge while reinforcement. Comparison of head pressure and vacuum pressure, because of its many features, such as small pressure and easy control, more suitable for reinforceing Dredger Fill which had low-intensity . If the head declined too large in drainage process, fine-grained soil would take place under the seepage pressure, Vertical drainage body was surrounded by fine-grained soil, causing the vertical drainage failure in part or in whole. Dredger fill load imposed by controlling the vertical row of declining water levels in water rates and water level drawdown. the tests indicate that, slow down a relatively small drainage have more advantages to dredger fill reinforcement at beginning . Slow drainage flow was more conducived to secondary pipe network expansion and extension of dredger fill macroeconomic performance in follow aspect :the pore water pressure variation, the cumulative amount of the settlement, the impact of the scope of the water, intensity growth. The performance of the micro-structure was soil stability and relative stability of an earlier time, inhibiting the formation of mud Paper. Micro-performance was that the stability of soil structure formated earlier and degree of stability was higher, inhibited the formation of mud Skin.reinforcment of dredger fill was dominated by the size of self-weight stress and length of drainage path in the stage of self-drainage. The dredger fill in reinforcement area which had the large additional stress and short drainage path ,the pore water pressure to dissipate faster, slightly larger degree of consolidation. The impact of the radius was a cone in self-drainage stage.Third, the small pressure in self-drainage stage could further formated soil structure, but can not met the construction needs.In this paper, imposed the pressure constantly by the different vacuum pump.Vacuum pressure did not have direction, and closely related to the transfer medium. Strengthening the dredger fill through the under side of the drainage, the water level of upper reinforce soil play a role in sealing.under the activity of vacuum pressure, Dredger fill performance the following engineering nature :Early in the reinforcement, due to evaporation and other environmental factors, the parameters in The middle large than both side of reinforcement soil . With the development of vacuum load time,The Soil parameters of the engineering geology and depth of the changes were not relevant. The duration of loading and the growth of effective stress of soil had a closely relatationship. Vacuum load radiated homogeneously,which lead soil close to drainage have a high degree of consolidation, did not have difference in the depth. If the soil away from drainage body, its consolidation degree and the additional stress are related, that is, the greater the pressure, the more drainage, the greater the degree of consolidation. Under activity of the load, Salt crystals set with the soil grains cemented together, salts transformed solution tothe cement medium of soil particles.Shear strength of soil increaseed greatly. Have been soil compaction, pore smaller particles continue to become larger.In the process of the soil-water separation, self-drainage, the vacuum pressure ,soil structure strengthen enhanced continuously. Structural unit in the early reinforcement stage was the side - side contact state or suspended state mainly. With the strengthening and reinforcement loads increase, gradual transition for the surface - edge contact state, emerged side - face contact form partly. Large and medium pore porosity developted, salt crystaled clearly. With the extension of time in the reinforcement process, salts gradually formed salt bridges, to strengthen the link between soil particles, structural strength increased obviously. Soil structure transited the honeycomb structure to the loose structure of the flocculation more closely to the structure transition of flocculation. In the reinforcement process, due to high content of clay mineral .in the early stage of dredger fill‘s reinforcement, a large number of soil particles existed as a single particleless than 2μm. Because of relatively stable hydrodynamic condition in the bottom soil, which had a high degree of consolidation.So, the hydrodynamic conditions of agitation was not conducive to the formation of soil structure.With the extension of time in the reinforcement process, soil particles less than 2μm less and less, As the free water discharge, the relative concentration increased. As a result of the effect of electrostatic and other molecular force of gravity, So that the distance between soil particles decreased Continuously, Some particles evolving as a basis set large tablets, so that soil structure was more stable.Finally, hydrogeological analysis of seepage thinking process introduced into analysis of the mechanism of soil reinforcement. Established the flow model under self-drainage conditions. In the early stages of pressure, soil drainage by the load, with the reinforcement of the extension of time, displacement tended to steady. Head line, such as soil reinforcement steep than the upper, relatively flat bottom. The lower part of the reinforced soil mass’s equivalent water head density than the upper part of the reinforced soil, noted the lower part of the soil drained more water than the upper part of the under pressure,those result resemble with the the test results of moisture content . Through the testing of indoor water flow model, founded that the farther away from the drain, the greater the error. Analysis of the main reasons was the flow channel in the process of reinforcement with the reinforcement of the extension of time to continue to expand and extend and hydrogeological parameter’s change. Therefore, only results of this article can be used for trend analysis, can not be used as the basis for a quantitative evaluation.更多还原