干湿循环对石灰处治膨胀土动力特性影响试验研究

发布时间：2018-03-05 15:51

本文选题：石灰处治膨胀土　切入点：物理力学性质　出处：《广西大学》2015年硕士论文　论文类型：学位论文

【摘要】：为研究干湿循环效应对石灰处治膨胀土强度特性的影响规律,本文以经石灰处治过后的南宁弱膨胀土为研究对象,通过一系列室内物理力学性质试验获取该膨胀土改性前后的物理力学性质指标,对三轴试样进行干湿循环试验,最后借助GDS动三轴仪对处治土开展静力三轴剪切以及振动三轴试验,主要研究内容如下：1.对掺灰比6%的石灰处治膨胀土开展一系列室内物理力学土工试验,试验结果表明：石灰处治土相比原膨胀土,比重降低,液限降低,塑限升高,塑性指数明显降低,最大干密度降低,最优含水率升高,由改性前的低液限黏土变性为低液限粉土,土样由高压缩性土变成了中低压缩性土,自由膨胀率、线缩率和胀缩总率等指标相较于处治之前有明显的降低,抑制了原膨胀土的胀缩性,改性后的膨胀土已属于非膨胀土范畴,抗剪强度指标也得到显著提升。2.对完成养护的三轴剪切试样进行干湿循环试验,对干湿循环的破坏效应进行了分析,认为干湿循环效应引起土体反复胀缩,导致土体内部裂隙的发育,降低了土颗粒间的连接程度,从而使处治土的结构性遭到破坏,且破坏程度随干湿循环的次数增加而增大。3.对完成0～5次幅度干湿循环且养护好的试样分组进行固结不排水三轴试验,试验表明干湿循环对处治土的影响宏观上表现为抗剪强度的不断衰减,第1次、第2次干湿循环后粘聚力衰减幅度较大,第3次循环后衰减幅度减小并趋于稳定,而内摩擦角仅在第1次干湿循环后有较大衰减,总体而言变化幅度相当小,对抗剪强度的影响很小。4.针对处治土的动变形特性,研究了0～5次干湿循环效应下的骨干曲线(σ～εd曲线)、动弹模量与动应变关系曲线(Ed～εd曲线、1/Ed～εd曲线)、阻尼比与动应变关系曲线(λ～εd曲线)的变化规律,研究了固结压力、固结比、动荷载频率等因素在干湿循环效应下对处治土骨干曲线、动弹性模量和阻尼比等的影响,得到了不同因素影响下的骨干曲线本构关系模型、动弹性模量衰减模型。根据等效线性模型(Hardin-Drnevich模型)提出的等效阻尼比公式,计算得到全应变范围内的阻尼比λ,根据试验结果确定最大阻尼比λmax；根据该模型提出的双曲线型动应力动应变关系,拟合计算得到最大动弹模量Edmax。
[Abstract]:In order to study the effect of dry-wet cycle effect on the strength characteristics of expansive soil treated with lime, the weak expansive soil in Nanning after treated with lime is taken as the research object in this paper. Through a series of indoor physical and mechanical property tests, the physical and mechanical properties of the expansive soil before and after modification were obtained, and the dry and wet cycling tests of triaxial specimens were carried out. Finally, the static triaxial shear and vibration triaxial tests were carried out on the treated soil by GDS dynamic triaxial test. The main research contents are as follows: 1. A series of indoor physical and mechanical geotechnical tests were carried out on the lime treated expansive soil with the ratio of 6% with lime. The test results show that compared with the original expansive soil, lime treated soil has lower specific gravity, lower liquid limit, higher plastic limit, lower plastic index, lower maximum dry density and higher optimum moisture content. From the low liquid limit clay to the low liquid limit silt before modification, the soil sample changed from high compressible soil to medium and low compressible soil. The free expansion ratio, linear shrinkage rate and total expansion rate were obviously decreased compared with those before treatment. The dilatancy and shrinkage of the original expansive soil are restrained, the modified expansive soil has already belonged to the category of non-expansive soil, and the shear strength index has also been significantly improved .2.The dry and wet cycle tests have been carried out on the triaxial shear specimens which have been cured. The failure effect of dry-wet cycle is analyzed. It is considered that the dry-wet cycle results in repeated expansion and contraction of soil mass, which leads to the development of internal cracks in soil, reduces the degree of connection between soil particles, and results in the destruction of soil structure. The degree of failure increases with the increase of dry-wet cycle times. The undrained triaxial tests are carried out on the samples which have completed 0 ~ 5 amplitude dry and wet cycles and have been cured. The experimental results show that the influence of dry and wet cycles on soil treatment shows the continuous attenuation of shear strength. The cohesive force decreases greatly after the first and second dry and wet cycles, and the attenuation amplitude decreases and tends to be stable after the third cycle. However, the angle of internal friction only attenuates after the first dry-wet cycle, and the variation range is quite small, and the influence of shear strength is very small. 4. According to the dynamic deformation characteristics of treated soil, In this paper, the variation law of the key curve (蟽 ~ 蔚 d curve, dynamic modulus of elasticity and dynamic strain curve) and the curve of damping ratio and dynamic strain (位 ~ 蔚 d curve) under the dry and wet cycle of 0 ~ 0 ~ 5 times are studied, and the consolidation pressure and consolidation ratio are also studied. The influence of dynamic load frequency and other factors on soil backbone curve, dynamic elastic modulus and damping ratio under dry-wet cycle effect is studied, and the constitutive relation model of backbone curve under different factors is obtained. According to the equivalent linear model (Hardin-Drnevich model), the equivalent damping ratio formula is presented. The damping ratio 位 in the range of total strain is calculated, and the maximum damping ratio 位 maxis determined according to the experimental results. According to the hyperbolic dynamic stress-strain relation proposed by the model, the maximum dynamic modulus Edmaxis obtained by fitting.
【学位授予单位】：广西大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU411;TU443

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