曹妃甸填海造陆区吹填土P-N固化试验与机理分析

发布时间：2018-09-05 10:59

【摘要】：填海造陆已成为缓解沿海地区土地资源紧张的有效途径,而吹填土造陆是填海造陆的主要方式。由于吹填土具有容重小、孔隙比大、含水量高、强度极低等特点,不能直接作为地基土使用,因此,采用化学固化剂对吹填土进行加固处理,以期提高吹填土强度,对填海造陆工程场地地基土处理具有重要的实践意义。本文以河北省唐山市曹妃甸填海造陆区吹填土为研究对象,以聚丙烯酰胺(PAM)和水玻璃(Na2Si O3)为固化剂,设计P-N(PAM和水玻璃)固化方案。在颗粒分析、击实试验、易溶盐分析、地下水分析、XRF成分分析等测试得到吹填土理化性质的基础上,通过无侧限抗压强度试验、三轴剪切试验等,对固化前后吹填土的变形和强度进行了对比分析,结合正交试验,分析了PAM和水玻璃掺入比例、养护龄期等因素对固化效果的影响程度,确定了最优固化方案。借助模糊评价法,对PAM和水玻璃单掺、双掺的固化效果进行了综合评价。对比研究了固化前后吹填土微观结构变化,并揭示了吹填土固化机理。研究表明:(1)曹妃甸填海造陆区吹填土为粉土,易溶盐以碱金属氯盐和硫酸盐为主,地下水水质偏碱性,其主要矿物成分为黏土矿物,属于碱性土。(2)单掺PAM固化吹填土的无侧限抗压强度、抗剪强度指标C、Φ均与PAM掺入比例和养护龄期呈正相关,随着PAM掺入比例和养护龄期的增加,三轴应力应变曲线从应变硬化型逐渐转化为应变软化型。(3)单掺水玻璃固化吹填土的无侧限抗压强度、抗剪强度指标C、Φ均与水玻璃掺入比例和养护龄期呈正相关,随着水玻璃掺入比例和养护龄期的增加,三轴应力应变曲线应变软化趋势不断增强,固化吹填土抗变形能力及强度均得到提高。(4)随着养护龄期的增长,P-N(PAM和水玻璃)双掺固化吹填土的无侧限抗压强度及C、Φ提高幅度越大,三轴应力应变曲线为应变软化型,抗剪强度和抗变形能力均得到提高。(5)根据模糊评价法对吹填土固化效果进行了综合评价,P-N(PAM和水玻璃)双掺好于单掺,单掺水玻璃好于单掺PAM。(6)养护龄期、固化剂掺入比例等对吹填土的固化效果影响程度由大到小分别为养护龄期水玻璃掺入比例PAM掺入比例;最优固化方案为PAM、水玻璃掺入比例分别为0.3%、4%、养护龄期28天。(7)固化前吹填土微观结构表现为松散、孔隙发育、孔径分布以超大孔和大孔为主,固化后吹填土微观结构表现为孔隙比和孔隙度减小、孔径则转变为以中孔及小孔为主、分维增大。养护龄期越长,固化吹填土的孔隙越少,孔径越小,分维越大。(8)PAM固化机理主要为絮凝作用、吸附作用及屏蔽作用,在颗粒间连接架桥形成网络结构,加强了吹填土颗粒胶结作用;水玻璃固化机理为黏土矿物与水玻璃间发生化学反应生成硅酸凝胶和硅酸钙凝胶颗粒,填充孔隙;P-N(PAM和水玻璃)固化的机理为PAM加强吹填土颗粒间凝聚力的同时,水玻璃能够与吹填土反应生成凝胶和沉淀填充孔隙。
[Abstract]:Reclamation has become an effective way to alleviate the shortage of land resources in coastal areas, and reclamation with dredged fill is the main way to reclaim land from the sea.Because dredged fill has the characteristics of small bulk density, large void ratio, high water content and very low strength, it can not be used as foundation soil directly. It is of great practical significance to improve the strength of dredged fill soil for the foundation soil treatment of reclamation and land-building engineering site.In this paper, the dredged fill soil in Caofeidian reclamation and land-building area of Tangshan City, Hebei Province, was taken as the research object, and the P-N (PAM) and water glass (Na2Si O3) solidification schemes were designed with polyacrylamide (PAM) and sodium silicate (Na2Si O3) as solidifying agents. Based on the analysis of soluble salt, groundwater and XRF components, the physical and chemical properties of dredger fill are obtained. The deformation and strength of dredger fill before and after solidification are compared and analyzed by unconfined compressive strength test and triaxial shear test. Combined with orthogonal test, the factors such as the proportion of PAM and sodium silicate, curing age and so on are analyzed. The optimum solidification scheme was determined. The solidification effect of PAM and sodium silicate mixed with single and double was evaluated by fuzzy evaluation method. The microstructure changes of dredger fill before and after solidification were studied and the solidification mechanism of dredger fill was revealed. The salt is mainly alkali chloride and sulfate, the groundwater quality is alkaline, and the main mineral is clay mineral, which belongs to alkaline soil. (2) The unconfined compressive strength, shear strength index C, _are positively correlated with PAM mixing ratio and curing age, with the increase of PAM mixing ratio and curing age, triaxial stress. (3) The unconfined compressive strength, shear strength index C and_of the dredger fill solidified with sodium silicate are positively correlated with the proportion of sodium silicate and curing age, and the trend of strain softening of the triaxial stress-strain curve increases with the increase of the proportion of sodium silicate and curing age. (4) With the increase of curing age, the unconfined compressive strength and C, _of P-N (PAM) and water glass mixed solidified dredger fill are increased, and the triaxial stress-strain curve is strain-softening type, and the shear strength and deformation resistance are improved. (5) According to the fuzzy evaluation method. The consolidation effect of dredger fill is evaluated comprehensively. P-N (PAM) and sodium silicate are better than single-doped, and single-doped sodium silicate is better than single-doped PAM. (6) The influence degree of curing age and the proportion of solidifying agent on the consolidation effect of dredger fill from large to small are respectively the proportion of sodium silicate in curing age; the optimum curing scheme is PAM and sodium silicate in curing age. (7) Before solidification, the microstructure of dredged fill is loosened, pore development, pore size distribution is dominated by super-large pores and macropores, and after solidification, the microstructure of dredged fill is characterized by porosity ratio and porosity reduction, pore size is mainly changed to mesopore and small pores, fractal dimension is increased. (8) PAM solidification mechanism is mainly flocculation, adsorption and shielding, bridging between particles to form a network structure, which strengthens the cementation of dredged fill particles; water glass solidification mechanism is the chemical reaction between clay minerals and sodium silicate to form silicate gel and calcium silicate coagulation. The solidification mechanism of P-N (PAM and sodium silicate) is that PAM can enhance the cohesion between particles of dredged fill, and water glass can react with dredged fill to form gel and precipitate to fill the pores.
【学位授予单位】：中国矿业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P756.8;TU41

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