【作者】 韩鹏举；

【导师】 白晓红；

【作者基本信息】 太原理工大学 ， 岩土工程， 2009， 博士

【摘要】 工程材料在污染环境下的耐久性研究是国际上非常关注的、尚未完全解决的科技热点问题,对于水泥土搅拌桩复合地基受环境影响后工程性质的劣化研究尚未看到有关报道,考虑这一因素的设计方法尚未提出。本文在收集、查阅及整理中外文献的基础上,以地基土（粉土）和水泥土为研究对象,总结在不同无机化合物环境条件下,地基土和水泥土的物理、化学和力学性质变化规律,探讨环境对粉土和水泥土工程性质影响的工作机理,为建立考虑环境影响的复合地基耐久性设计理论,确保工程长期安全,降低工程成本以及无机化合物环境下水泥土搅拌桩复合地基的安全性评价标准起到技术支撑作用,为我国的国民经济建设和社会发展具有积极意义。主要研究成果归纳如下:1)通过室内模拟试验,对浸泡于不同类型、浓度的碱（NaOH和NH₃·H₂O）溶液和盐（NaCl和Na₂SO₄）溶液中的粉土试样进行了物理力学指标的测定,总结了其与介质的类型、浓度之间的变化规律:碱溶液中的土样,随着溶液浓度的提高,土样的密度、液限、塑限、塑性指数、压缩系数a1-2均有所增加,孔隙比有所降低,横向比较NaOH溶液和NH₃·H₂O溶液中土样的各项指标发现,NaOH对于土样的影响要强于NH₃·H₂O;盐溶液中的土样,随着溶液浓度的增加,土样的密度、比重随之增加,孔隙比、液限、塑限、塑性指数和压缩系数均随之降低,横向比较NaCl溶液和Na₂SO₄溶液腐蚀后土样的各项指标发现,Na₂SO₄对于土样的影响要强于NaCl,说明SO₄^2-比Cl^-对土样的影响大;并且得到了各种溶液下液限与塑性指数的线性关系,建立了土样的压缩系数与溶液浓度的指数分布数学关系,在实际工程中可供参考。2)基于污染介质对地基土侵蚀的迁移规律主要是渗透和扩散,考虑了迁移过程中的化学反应,建立了污染介质在地基土中的迁移模型。3)H₂SO₄溶液环境、MgSO₄溶液环境和Na₂SO₄溶液环境下水泥土表观现象变化明显,主要表现为表面起皮、软化,棱角处饨化或开裂;MgCl₂溶液环境和CaSO₄溶液环境中的水泥土表观现象主要表现为表面附着结晶物,试块尺寸基本没有变化。4)通过测试不同时间下各种环境的水泥土抗压强度,提出了各种环境下的水泥土强度修正系数,并且得出:CaSO₄环境、MgSO₄（1.5g/L）环境、Na₂SO₄（1.5g/L）环境和MgCl₂（1.5g/L）环境下的水泥土强度修正系数均大于1,说明这几种环境对水泥土强度的增长有利;而其他环境下的强度修正系数均小于1,对水泥土不利,因此在工程应用中,应根据环境的不同而采取相应的措施,在保证工程的安全性前提下,优化设计,降低成本;通过分析各种环境下水泥土的应力应变关系曲线,在已有水泥土本构模型的基础上,考虑环境引起的水泥土强度损失建立了无机化合物环境下水泥土的应力应变关系方程。5)由水泥土的表观现象和水泥土强度的修正系数,得出各种无机化合物环境对水泥土作用的大小排序为Na₂SO₄>MgSO₄>H₂SO₄>MgCl₂>CaSO₄。当溶液当中都存在SO₄^2-时,阳离子对水泥土作用大小排序为:Na⁺>Mg²⁺>H⁺>Ca²⁺;当溶液都存在Mg²⁺时,阴离子对水泥土作用大小排序为:SO₄^2->Cl^-。6)通过测试水泥土不同浸泡时间下各种环境中主要介质的浓度,揭示了各种环境中主要介质的变化规律:H₂SO₄环境中pH值随时间增长有不同程度的升高,SO₄^2-浓度随时间增长有不同程度的降低;MgSO₄环境中Mg²⁺浓度随时间增长有不同程度的降低,SO₄^2-浓度随时间增长14天以前升高、14d后有不同程度的降低;Na₂SO₄环境中的Na⁺浓度和SO₄^2-浓度随时间增长有不同程度的降低;CaSO₄环境中Ca²⁺和SO₄^2-浓度随时间增长有不同程度的降低;MgCl₂环境中Mg²⁺浓度随时间增长有不同程度的提高,Cl^-浓度随时间增长在7天前升高,7d后有不同程度的降低。7)对各个环境的主要介质进行计算、对比分析揭示了环境对水泥土的作用机理,其中H₂SO₄、MgSO₄和MgCl₂环境对水泥土腐蚀是分解型腐蚀与结晶型腐蚀的复合型腐蚀;Na₂SO₄环境对水泥土腐蚀是溶出型腐蚀与结晶型腐蚀的复合型腐蚀;CaSO₄环境对水泥土无腐蚀作用。根据各种环境中的主要介质浓度与水泥土强度的关系建立了相应的水泥土强度模型,并给出了各种水泥土强度模型的适用范围。8)提出了水泥土搅拌桩复合地基的耐久性研究内容有复合地基的耐久性机理、在役水泥土搅拌桩复合地基的耐久性评估和剩余寿命的预测、拟建复合地基的耐久性设计和提高耐久性的技术措施。根据水泥土搅拌桩复合地基所处的环境,考虑时间效应,提出环境腐蚀下水泥土搅拌桩复合地基的承载力的设计公式和复合模量计算公式。将水泥土搅拌桩复合地基耐久性分为A～D四个等级,并根据模糊评判理论建立了考虑桩体耐久性和桩间土耐久性的水泥土搅拌桩复合地基耐久性模糊综合评判模型。更多还原

【Abstract】 Study of engineering material durability in the corrosive environment is one of international highly attention objects. It is hard to find the report relevant to engineering property study of cemented soil column composite foundation working in a corrosive environment and the design method is also rare to the environment pollution effect on the foundation durability. Based on collecting, checking and summarizing domestic and foreign literatures, this thesis studies the physical, chemical and mechanical properties and working mechanism of silty soil and cemented soil under various inorganic compound environmental conditions. This work has positive meaning for establishing composite foundation durability design theory and safety evaluation standard considering environment action, insuring the long-term engineering safety, lowering the engineering cost, promoting our country economy and society development.The main achievements are as followed:（1） Through the analogous experiment in lab, the physical and mechanical indexes are taken for the silty soil samples soaked in the alkaline solutions （NaOH and NH₃.H₂O） and saline solutions （ NaCl and Na₂SO₄） with various concentrations. The test results show that density, liquid limit, plastic limit, plasticity index, compression coefficient are increased and void ratio is decreased for the samples soaked in alkaline solutions with the increment of the concentration; compared with the test data, the effect of NaOH solution on the sample is stronger than that of NH₃.H₂O solution. The density and specific gravity of soil particle are increased, and void ratio, liquid limit, plastic limit, plasticity index, compression coefficient are decreased for the samples soaked in saline solutions with the increment of the concentration; compared with test data, the effect of Na₂SO₄ solution on the sample is stronger than NaCl, which may be the result of SO₄^2- stonger than Cl^-. Based on the test data, the statistical functions are set up, such as the linear function of liquid limit and plasticity index, exponential function of compression coefficient and solution concentration, which could be used in actual engineering.（2） According to the migration regulation of contamination in subsoil, primarily migration types are permeating and diffusibility. The migration model of pollutant ingredients in the foundation soil is established, in which the chemical reaction in the migratory process is taken into account.（3） In order to simulate and study the erosion effect process, the photos of the cemented soil samples are taken, when they are soaked in various inorganic compound solutions with different concentrations and times. The out-looks of the samples are obviously changed, mainly represent the surface soften, the size reduced or crack, when they are soaked in H₂SO₄, MgSO₄, Na₂SO₄ solutions. However, the out-looks of the samples soaked in MgCl₂ and CaSO₄ solutions are changed but not seriously, mainly represent crystallization adhering to the surface.（4） At the meantime, the unconfined compression tests are conducted on the cemented soil samples which are soaked in the inorganic compound solutions with various concentrations and times. The cemented soil strength modified coefficient under each corrosive environment is obtained, and the cemented soil strength modified coefficient are great than 1 for the CaSO₄, MgSO₄ （1.5 g/L）, Na₂SO₄ （1.5g/L） and MgCl₂（1.5g/L） solution environments, from which it may be drawn out that these environments are beneficial to the strength increasing of cemented soil. All of the strength modified coefficient for the other solution environments are less than 1, from which it may be drawn out that these environments propose the corrosion to the cemented soil and reduce the strength. Therefore the working environmental condition of the composite foundation should be taken into account when designing and calculating the foundation bearing capacity and settlement in order to optimize design, reduce the cost, adopt suitable measures, and assure the safety. Additional, full stress-strain curve of cemented soil is obtained too. Based on the existing damage model and test data, a modified stress-strain equation is set up for inorganic compound environment considering the cemented soil strength lost caused by environment affect.（5） The test results show that some inorganic compound solutions give cemented soil higher influence than others. In this experiment, inorganic compound solutions can be arranged in a series for the influence as follows: Na₂SO₄ > MgSO₄> H₂SO₄> MgCl₂> CaSO₄, When the solutions exsits SO₄^2- ion, the influence degrees of cations Na⁺, Mg²⁺, H+, Ca²⁺ are Na⁺> Mg²⁺> H⁺> Ca²⁺; When the solutions exsits Mg²⁺ cation, the influence degrees of SO₄^2- anion is greater than that of Cl^- anion.（6） The concentration of the main chemical ingredients in the solutions are measured when the cemented soil samples are soaked in the solution for different times. For the H₂SO₄ solutions, the pH value is increasing, and the SO₄^2- concentration is decreased with the increment of erosion time; for the MgSO₄ solutions, Mg²⁺ cation concentration is decreased with the increment of erosion time, but SO₄^2- anion concentration is increasing when the sample soaked time is less than 14 days, then decreasing when the soaked time greater than 14 days; for the Na₂SO₄ solutions, Na⁺ concentration and SO₄^2- concentration are decreased with the increment of erosion time; for the CaSO₄ solutions, Ca²⁺ concentration and SO₄^2- concentration are decreased with the erosion time increasing; for the MgCl₂ solutions, Mg²⁺ concentration is increasing with the erosion time increasing, Cl^- concentration is increasing before first 7 days, then decreased after 7 days.（7） By calculating main chemical ingredients and analyzing the mechanism, the corrosive type of H₂SO₄, MgSO₄ and MgCl₂ solutions to cemented soil is a composite type of resolving and crystallizing combination; that of Na₂SO₄ solution to cemented soil is a composite type of dissolving and crystallizing combination; CaSO₄ solution shows no corrosive action to the cemented soil. Based on the relationship of the main ingredient concentration of the solution and cemented soil strength, the cemented soil strength model is established for each corrosive type, the limit for each model is also described.（8） The research contents of cemented soil column composite foundation contain durability mechanism, durability valuation, estimate of its surplus life, durability design and technique measure to increase durability. Based on the environment condition surrounding the cemented soil column, the design formula of the bearing capacity and composite modulus for this composite foundation are proposed in this thesis, in considering corrosive time action. Finally, the durability of the cemented soil column composite foundation are classified into A～D four grades, and composite foundation durability assessment model is established with considering the column durability and surrounding soil durability based on the fuzzy assessment theory.更多还原