Research On Lab Simulation Test Of Quick Consolidation Technique For Dredger Fill With High Clay

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.