| There are much quaternary reticulate red clay which is formed by pluvial and widely distributed in Wuhan city. Red clay’s main clay mineral composition are kaolinite and illite, containing a small amount of chlorite. The non-clay mineral are quartz, feldspar and mica. This kind of red clay has the following characteristics:medium-porosity,high-plasticity, medium-water content, medium-low compressibility, in-weak swelling, etc. Red clay is widely distributed and used as a building material and foundation for county dirt roads, temporary roads, construction sites and anti-seepage projects. Red clay easily suffered the influence of water softening, however, can cause a lot of engineering diseases, such as fracture, red clay in the soil and water body, uneven subsidence of foundation and fracture damage infrastructure. When surface water are into the fractured red clay, soil softening, poor project performance and slope and landslide take place.Therefore, it is very necessary and urgent to carry out e in-depth study on red clay modification.The research adopts Ionic Soil Stabilizer (ISS) as chemical reinforcement on red clay. ISS is a complex anionic surfactant. After joining the red clay, it spread on the surface of the soil particles, not only wetting soil particle surface and capillary,but also stagnating the soil particle surface and capillary.ISS exchanges with red clay surface exchangeable cation and polarity water molecules, thereby reducing soil particle surface charge, thinning clay diffusion layer thickness, improving the water stability and increasing the intensity.Therefore cation exchange adsorption is a primary part of soil properties change. Cation exchange capacity, especially in major change quantity of cation exchange process, is the study of ISS curing mechanism and evaluation of the important indices for curing effect, Domestic and foreign counterparts in the study mainly discuss laboratory analysis of curing effect of red clay disturbance.The undisturbed sample of red clay reinforcement research has not yet carried out in-depth. The research on undisturbed in-situ reinforcement in red clay distribution area, has an important engineering significance.The research develops a set of real-time online detection of variable water head permeable soil column system based on laser breakdown spectroscopy (LIBS) to carry out the distilled water infiltration test of red clay, to understand the basic changes of cation after distilled water infiltrates soil. The ISS aqueous solution infiltration test of red clay is conducted to simulate the undisturbed in-situ reinforcement in red clay distribution area. Distilled water seepage test of red clay with ISS reinforcement is conducted to verify the durability of the modified soil strength, namely the ISS modified irreversibility of red clay.The following researches have been carried out:(1) The test method is primary to research and key technology in the research on the main cation migration under the condition of different switching. The dissertation first introduces the common method of barium chloride buffer of the total cation exchange on geotechnical engineering, but its experimental technology operation has too much human disturbance factors. Then introduces the plasma emission spectrometer (ICP-AES) test the main cationic and anionic type DX-120 ion chromatograph test sample preparation, measurement method, finds that the technology is superior to the traditional laboratory chemical titration method, but the preprocessing is complex, and cannot satisfy the requirement of in situ testing. The dissertation selects the advanced laser breakdown spectroscopy (LIBS) to detect the migration process of the cation. The technology can be real-time, on-line, multi-element detection at the same time, meeting the ISS curing mechanism study, revealing the demand of the cation exchange process, and implementing in situ test.(2) The research develops a set of LIBS real-time online detection based on the system of varying head infiltration and soil column through experiments of distilled water permeable into clay and soil.①The basic physical experiment with crystalline structure of soil, red clay and expansive soil clay minerals and basic physical and chemical properties, as well as the experimental sample preparation are introduced in detail.②The test kit is the ISS aqueous solution with different ratio of water.ISS water solution is ionic soil stabilizer with high sodium content. ③The test of the surface tension of aqueous solution of different ratio of the ISS makes use of the common maximum bubble pressure method, the results of which show that the surface tension of ISS aqueous solution under different ratio is significantly less than the pure water, and surface tension decreases with the increase of the density. It indicates that ISS dissolved into water can reduce the surface tension of water.④The pH value and conductivity of ISS aqueous solution under different ratio are tested with the use of FG2 METTLER TOLEDO portable pH meter and FG3 METTLER TOLEDO portable conductivity meter. The results show that ISS aqueous belongs to acidic solution with high electrical conductivity which rises with the increase of concentration of ISS solution. ⑤The lower plasticity index after the accession to the ISS of the red clay can determine the optimum mixture ratio of ISS reinforced soil. The optimal ratio between water solution and water is about 1:150.(3) By conducting distilled water infiltration soil test of red clay, the ISS aqueous infiltration soil test of red clay and distilled water infiltration ISS modified test of red clay, four kinds of cationic K+、Na+、Ca2+、Mg2+ion concentration are got in different time node, thus studying cationic migration process under the conditions of different permeability.①In the process of distilled water infiltration into red clay, clay minerals content of k+、Na+、 Ca2+、Mg2+ etc., under the action of distilled water, are out of the soil column to exudates. The cation concentration peak gradually, as the new hydration environment affecting structure into balance, the ion concentration gradually decreases, so the overall trend is on the increase after the first cut.② In the process of the ISS infiltration into red clay, first the Na+ ions in ISS aqueous solution with its concentration of absolute advantage, will be on the surface of clay particle interchangeability with high cation exchange, occupying the position of soil particle surface and its concentration drops sharply. The Ca2+、Mg2+ion exchange out peak concentration increased gradually.It is the surface balance stage. This stage is a relatively short time. Inner surface equilibrium phase is longer.The ISS aqueous solution relies on the "head" and red clay particles formed by surface chemical chain effect, occupying the red clay particles on the surface of a cationic vacancy, and is adsorbed on the surface of clay minerals.;ISS "hydrophobic tails" around the soil particle surface form an oily layer, preventing moisture from entering the system. The ion exchange gradually slow, Ca2+、Mg2+ ion concentration gradually decreases, and the penetration of Na+ ion aqueous solution as the ISS concentration increased slowly. Finally, after new hydration environment balance stable, clay particles with stable seepage channel, and the ion concentration in the late to the ion concentration in aqueous solution with ISS tends to increase or decrease. Test results indicate a preliminary inference, the time which ISS aqueous solution and the clay are completely functioned is about 1-2 days.③ In the process of distilled water penetration into ISS modified red clay, the surface modification of clay in the combination of ion exchange water quantity is less, the smaller the degree of ion exchange. Ion exchange capacity is weak, with the smaller the negative electricity, its hydration expansion and dispersion ability is weak, the combined water film thickness is thin. Clay to the change of medium physical-chemical conditions is not sensitive to the nature of the soil,it is more difficult to change. the Na+ concentration increases after the first decreases, and the concentration of K+、Ca2+、Mg2+ gradually reduce.④ The conductivity can reflect the content of the solution. Three penetration mode measure the change trend of the electrical conductivity of a logarithmic normal distribution are, first, after the reduction, finally leveled off value, cation concentration change trend is consistent.(4) The research takes the red clay as an example to introduce changes of red clay samples in the modified correlation of soil mechanics index, to illustrate the consolidation effect and to reveal the consolidation mechanization. ①We use the F-Sorb3400 specific surface area and pore size tester to test the pigment of expansive soil. After ISS reinforced red clay, soil particles treated by ISS particle size increased, leading to the soil particle surface area decreased, reflecting the increasing the particle size.②The use of fast shear method is a series of direct shear test, results showed that the addition of ISS after the red clay cohesion increases obviously, but the angle of internal friction is almost unchanged, and the shear strength of soil from the mechanism to explain the reasons for this phenomenon.③Red clay reinforced expansive before and after the comparative study, carrying out ISS can see, after joining ISS, the red clay free expansion rate decreases, line shrinkage, shrinkage, shrinkage limit body also has different rate reduce. Free expansion rate decreased, illustrates the red clay after ISS treatment, expansion was decreased, decreased water sensitivity; soil linear shrinkage ratio, that is adsorbed on the clay particle surface part of the combination of the water has been replaced, to strengthen the connection force between soil particles and particles, native body shrinkage deformation capacity becomes small.④The consolidation tests of compression coefficient and compression modulus of soil by using consolidation apparatus. After ISS treatment, reduce the compression coefficient of red clay, compression modulus increases, which further proves that the red clay after ISS treatment, soil pore decrescent, the soil becoming more dense, hard to improve the soil skeleton, so in effect under the same pressure, enhance the ability of ISS cured samples are subjected to external load, resistance deformation ability improvement.⑤In order to study the red clay reinforced by ISS, the red clay on the water sorption potential changes, to carry out the research on soil water characteristic curve, found that the matric suction of red clay samples and ISS cured samples are increased with decreasing water content and matrix suction, and in the higher range, influence of water content on soil water characteristic curve effect decreases.(5) After the scanning electron microscopy, test shows that the mineral soil mass after the ISS penetration effect become bigger, particle cementations are more closely, and ranks are relatively tidy uniformly, pores are reduced at the same time, the original big pore is filling and cementing, the soil structure is relatively stable, the soil particles adsorption with combined water space are reduced, pore permeability is reduced, mechanical properties are enhanced.(6) The research is conducted from the change of soil microstructure, the action of water in the soil and the main cationic movement spread way to modification mechanism of ionic soil stabilizer.Through comparing the original red clay and the modified red clay’s migration and permeability of soil mechanical property change under three different permeability conditions, the research shows the soil can be penetrated through the static way of in-situ reinforcement. The reinforcement of soil indicates longer strength. The research provides an important laboratory reference on the study of the mechanism of ISS and in situ undisturbed strengthening ISS engineering practice in red clay area. |
PDF Full Text Request