【作者】 曹友杰；

【导师】 周训；

【作者基本信息】 中国地质大学(北京) ， 水文学与水资源， 2012， 博士

【摘要】 在地震等周期性动荷载作用下，饱和砂土或粉土及砂质粉土等少粘性土极易产生液化现象，从而造成地基失效，对建筑物或其它地面设施造成损坏。在地震动荷载一定的情况下，影响饱和土液化的主要是其颗粒组成以及密实程度、地下水位埋深和上覆非液化土层的厚度等因素。为减轻液化震害造成的损失，研究有效的抗液化措施十分必要。本文以郑州市郑东新区为研究对象，在深入探讨液化机理和液化判别方法的基础上，以野外钻探、原位测试和室内试验为主要手段，对研究区可液化土进行了一系列勘察工作，查明了研究区内可液化土的物理力学特征。对研究区所处自然地理地质条件和水文地质条件及地震工程地质条件进行了说明，并对区内饱和少粘性土的液化可能性和液化等级进行了判别和评价。总结了研究区内可液化土的物理力学特征，查明了其平面分布特征及深度分布特征。对研究区可液化土的震陷可能性进行了分析评价，对研究区可液化土的特性进行了综合评价。为提出有效的抗液化措施，分别对几种常用的抗液化措施如强夯法、砂石桩法、桩基础法等地基处理方法的抗液化机理以及处理效果进行了研究分析，提出采用水泥搅拌桩法作为抗液化措施的可行性，并从其抗液化机理上进行了论证。通过具体工程实例的类比分析，指出了桩基础作为抗液化措施的不足之处，对地基土抗液化处理措施进行了优化组合，提出减震隔离抗液化地基处理新理念和新模式。研究结果表明，在地震设防烈度为7度的地震背景下，研究区域内存在轻微-中等液化等级的可液化土，可液化土层埋深不超过16 m，属于液化和可能液化场地，应按照抗液化措施要求对建筑物地基进行相应处理。除了常用的强夯法和砂石桩法等抗液化处理措施外，水泥搅拌桩同样是可行的，原因是水泥中的细粒含量改变了土的颗粒组成。上述地基处理方法的地基承载能力一般不超过200kPa。对不同抗液化措施进行了优化组合，达到较好抗液化效果。同时提出了减震隔离抗液化地基处理新理念及实施模式，并经模型试验论证了该方法的有效性。更多还原

【Abstract】 Purpose: Effected by periodic dynamic loads as earthquake, soils with lower viscosity such assaturated sand soil, silty soil or sandy silt are easy to be liquefied, which will lead to the failure offoundations where structures or other facilities may be damaged. With the dynamic loads ofearthquake fixed, main factors influencing the liquefaction of saturated soils are its granules,compaction, depth of water level underground and thickness of covered non-liquefied soils. Inorder to reduce the loss caused by liquefaction-induced damage, it is very necessary to researchefficient anti-liquefaction measures. In the paper, Zhengdong New District is taken as subjectinvestigated, on the basis of deep discussion on the liquefaction mechanism and judging methodsfor liquefaction, the paper, which takes field drilling, in situ test and indoor test as main measures,conducts a series of investigation on the liquefiable soils in the investigated area, and determinesphysical mechanical characteristics of the liquefiable soils. Meanwhile, it describes physicalgeography, geologic conditions, hydrogeology and seismological engineering geology in the area,and makes judgment and appraisal on the possibility of liquefaction of low-viscosity soils and theliquefaction level in the area. It summarizes physical mechanical characteristics of the liquefiablesoils and investigates the characteristics of horizontal distribution and depth distribution. Itanalyzes and appraises the possibility of seismic settlement of liquefiable soils and gives overallappraisal on the characteristics of liquefiable soils in the area.Contents and Methods:In order to take efficient anti-liquefaction measures, the paper conducts studies and analysisupon the anti-liquefaction mechanism and treatment effect of foundation treatment methods suchas dynamic consolidation, sand-gravel pile, and pile foundation, etc, and advances the feasibilityof cement mixing pile to resist liquefaction, and makes discussions in the anti-liquefactionmechanism. Through the analogy analysis of specific construction cases, it indicates the deficiencyof pile foundation for anti-liquefaction, and optimizes and combines the anti-liquefactionmeasures of foundation soils, and lodges new ideas and patterns of damping isolation belt to be setaround buildings.Main Views and Conclusion: under the earthquake intensity of level 7, there are liquefiable soilsunder slight-medium liquefaction level in the investigated area, and the setting depth of liquefiablesoil shall be not more than 16m, which belongs to liquefiable and possibly liquefiable fields, thefoundation of structures shall be treated according to the requirements of anti-liquefactionmeasures. Except general anti-liquefaction measures as dynamic consolidation, sand-gravel pile,the cement-mixing pile is feasible as well, because the fines contents in cement change theformation of soil particles, and the contents of cosmid can be increased by about 3%. In theabove-mentioned foundation process method, the bearing capacity of foundation will generally notexceed 200kPa. The anti-liquefaction measures shall be optimized and combined as to reach anideal liquefaction effect. In addition, it lodges new ideas and patterns of damping isolationfoundation for anti-liquefaction, model tests indicate that the method works well to improve theanti-liquefaction of buildings, and the cycle index of stresses needed for liquefaction and damagesof buildings are increased by 40-50% respectively, in addition, the paper gives suggestions for thenext procedures.更多还原