含粘粒砂土抗液化性能的剪切波速表征研究

发布时间：2018-03-19 07:23

本文选题：地震液化　切入点：含粘粒砂土　出处：《浙江大学》2013年硕士论文　论文类型：学位论文

【摘要】：近年来,全球破坏性地震频发,破坏严重,造成了巨大的生命和财产损失,其中场地地震液化问题尤为突出。1999年土耳其地震、台湾集集地震中出现了大量含粘粒砂土场地液化震害。由于受到室内试验技术的限制,已有研究大多集中在洁净砂液化问题,对含粘粒砂土的地震液化性能研究很少,其液化评价问题亟待解决。只有深入理解含粘粒砂土结构性和动力特性,科学揭示含粘粒砂土场地地震液化机理,建立抗液化性能的表征与评价指标,才能为含粘粒砂土液化判别提供科学依据。本文针对含粘粒砂土抗液化性能评价问题,以剪切波速为表征参数,开展了多尺度试验研究,包括微观结构电镜观测,测量剪切波速的固结、静三轴与动三轴单元体试验,测量剪切波速的土工离心机振动台试验,以及震害现场调查研究,揭示了含粘粒砂土结构性对土体剪切波速与抗液化强度的影响规律,发展了含粘粒砂土抗液化强度与剪切波速间的定量相关关系。研究表明： 1、随着粘粒含量(CC)增加,含粘粒砂土结构性改变,其液塑限、渗透性、压缩性等物理力学性质发生相应变化；当CC超过一定临界值后,土体完成由“类砂土”向“类粘土”的转变,并表现出明显的“塑性”；剪切波速测量表明,当土体处于“类砂土”阶段或处于“类粘土”阶段,其Hardin公式拟合参数A与,7呈现出显著不同的规律；在没有颗粒破碎的前提下,不同粘粒含量砂土的临界状态线在e-log p'空间可近似用直线表示,且随着粘粒含量增加,其临界状态线沿顺时针方向偏转,土体剪胀势和临界状态摩擦角逐渐降低。 2、通过理论推导和不同粘粒含量砂土的测量剪切波速动三轴试验,建立了含粘粒砂土的CRR-Vs1幂函数相关关系,该相关关系表明,当粘粒含量低于临界细粒含量时,含粘粒砂土的CRR-Vs1相关关系曲线随粘粒含量增加逐渐上移,该趋势与以往研究结论一致,为含粘粒砂土抗液化强度的剪切波速评价提供了定量依据。 3、针对不同粘粒含量砂土,开展了多组土工离心机振动台液化试验,建立了含粘粒砂土模型地基制备与饱和方法,利用弯曲元技术监测了模型场地均匀性及试验过程中的剪切波速变化,再现场地喷水冒砂液化现象;通过含粘粒砂土与洁净砂对比试验,系统研究了模型地基内动应力应变关系、模量、阻尼以及孔压响应的发展规律；发现了模型尺度液化响应与单元体尺度液化性能的异同,提出了将振动台台面加速度作为地震动输入、基于孔压测试结果判别液化与否的模型地基地震液化分析方法,实现了利用离心机振动台试验数据进行场地液化判别的突破,由此验证了单元体尺度建立的含粘粒砂土CRR-Vs1相关关系的可靠性。 4、开展1999年台湾地区集集地震、土耳其Kocaeli地震的地震液化现场调查研究,建立了含粘粒砂土地震液化现场数据库,分析了所提出的含粘粒砂土CRR-Vs1相关关系对实际场地液化判别的适用性与可靠性。在此基础上,提出了设计地震下含粘粒砂土场地液化判别方法和计算步骤,并建议了主要参数的获得方法与推荐取值。
[Abstract]:In recent years, the global earthquake frequent, serious damage, caused a huge loss of life and property, the seismic liquefaction problem is particularly prominent in Turkey.1999 earthquake in Taiwan, the emergence of a large number of sand liquefaction damage in clay containing earthquake. Due to laboratory technical limitations, most research has been focused on clean sand liquefaction the problem, little research on seismic liquefaction properties of clayey sand, the liquefaction evaluation problems need to be solved urgently. Only understanding the structural and dynamic properties of clay containing sand, clay sand containing science reveals the earthquake liquefaction mechanism, establish the evaluation index and characterization of liquefaction, liquefaction containing clay can provide a scientific basis.
Aiming at the problem of evaluation with clay sand liquefaction resistance performance, using shear wave velocity parameters. The experiment was conducted to study the multi-scale, including micro structure of electron microscope observation, the consolidation measurement of shear wave velocity, static and dynamic three axis three axis unit test, measurement of shear wave velocity of geotechnical centrifuge shaking table test, and field investigation of earthquake damage the research reveals, containing clay sand structure on shear wave velocity of soil liquefaction resistance and the influence law of development of anti liquefaction strength and the quantitative relationship between shear wave velocity of sand clay containing studies:
1, with the increase of clay content (CC), containing clay sand structural change, the permeability of the liquid and plastic limit, compression, and other physical and mechanical properties change; when CC exceeds a certain critical value, the soil to complete the transformation from "type sand" to "clay", and showed a clear plastic "; shear wave velocity measurements show that, when the soil is in" sand "phase or in" clay "stage, the Hardin formula fitting parameters A and 7, showing a significantly different pattern; without particle breakage, the critical state line with different clay content of sand in the e-log space can be approximated by p'a straight line, and with the increase of clay content, the critical state line in a clockwise direction deflection, soil dilatancy and critical state friction angle decreases gradually.
2, by measuring the velocity of shear wave theory and different content of clay sand three triaxial test, CRR-Vs1 established a power function relationship with clay sand, show that the correlation between when the clay content is lower than the critical content of fine particles, including clay sand CRR-Vs1 correlation curve with the increase of clay content gradually rise, the same trend from the previous studies, which provides a quantitative basis for evaluating the shear wave velocity of sand clay containing anti liquefaction strength.
3, for the sandy soil with different clay content, carry out multiple groups of geotechnical centrifuge vibration liquefaction tests established by saturated method containing clay sand foundation model, shear wave velocity change model field uniformity and test in the process of monitoring by bending element technique, and then the scene spraying sand liquefaction by containing clay; clean sand and sand modulus contrast test, stress-strain relationship model in the foundation of dynamic system to study the development law of damping and pore pressure response; found the similarities and differences between the model scale and liquefaction response unit scale liquefaction performance, the vibration table acceleration as seismic input, the pore pressure test model of earthquake liquefaction whether or not the result analysis method of liquefaction discrimination based on, to achieve the site liquefaction breakthrough by centrifuge shaking table test data, which verifies the unit scale established Reliability of CRR-Vs1 correlation in clay sand soil.
4, to carry out the Taiwan area in 1999 Chichi earthquake, investigation of earthquake liquefaction site of Turkey Kocaeli earthquake, established the clay sand liquefaction site database, analyzed with CRR-Vs1 related to the actual site of clay sand liquefaction the applicability and reliability of the proposed relationship. On this basis, the proposed method and calculation steps of sand liquefaction containing clay under the design earthquake, and the main parameters obtained with the method recommended values.

【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU441

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