基于冻土动荷载直剪仪的高温冻土动力特性研究

发布时间：2018-01-18 16:00

本文关键词：基于冻土动荷载直剪仪的高温冻土动力特性研究　出处：《北京交通大学》2015年博士论文　论文类型：学位论文

【摘要】：我国多年冻土分布十分广泛,其中大部分都属于高温冻土,同时,青藏高原是我国地震活动水平最高、强度最大的区域。在这一区域运营中的青藏铁路、青藏公路等一批具有战略意义的重大项目,受到冻土温度升高、可能发生地震等因素的威胁。针对这一情况,研发测定冻土动力学参数的新型仪器,对低围压下高温冻土的动力学规律进行研究,并给出一定条件下高温冻土动力学参数的经验公式。对路基工程抗震设计、计算均有参考价值,对保障青藏高原上构筑物的安全运营具有重要意义。本文以国家重点基础研究发展计划(国家“973”计划)“冻土工程构筑物服役性能评价与预测(No.2012CB026104)'为依托,以青藏高原地区典型粉质粘土为研究对象,在总结国内外研究现状的基础上,通过现场调查取样、仪器开发、室内试验等手段,研究了低围压情况下高温冻土的动强度、动剪切模量和阻尼比等重要动力学参数。试验结果给出了不同影响因素对高温冻土动力学参数的影响关系,为高温冻土地区构筑物抗震设计、计算提供了较为适用的参数,并验证了新型试验仪器的适用性。主要成果有包括以下几个方面： (1)在总结和分析国内外研究现状的基础上,指出目前研究的不足之处,认为低围压下高温冻土的动力学特性缺乏系统性的研究,并以此为研究的重点。 (2)通过现场实地调研,选取典型场地并进行监测,并开展相关的室内土工试验,掌握了土样的基本土性,为进一步研究青藏高原粉质粘土的动力学性质打下基础。 (3)给出了冻土动荷载直剪试验系统各个组成部分的研制过程及相关参数的确定。分别分析了仪器的液压动力系统、可控温直剪盒、作动器与工作平台的拼接等方面的设计,并通过控温效果试验和不同情况的动直剪试验初步验证了新型仪器的试验精度和适用性。 (4)根据土的动强度理论对高温冻土进行了系统的研究。通过一系列不同温度、围压、振动次数条件下的动三轴、动直剪试验,得到了不同条件下土体的动强度参数。重点分析了温度和振动次数对其动强度的影响规律,并就两种试验方法及试验结果的异同点进行对比分析。 (5)通过总结土动力学本构关系,并结合动三轴、动直剪两种试验得到的试验结果,确定采用Hardin-Drnevich动本构模型对试验结果进行研究。系统的分析了温度、围压、振动次数等因素对动力学参数的影响关系,并对比分析了两种试验方法在测定动剪切模量、阻尼比时的异同,进一步验证了新型试验仪器的适用性。
[Abstract]:Permafrost is widely distributed in China, most of which belong to high temperature permafrost. At the same time, the Qinghai-Tibet Plateau is the region with the highest seismic activity level and the highest intensity. A number of important projects of strategic significance such as the Qinghai-Tibet Highway are threatened by factors such as the rise of frozen soil temperature and the possibility of earthquakes. In view of this situation, a new instrument for measuring the dynamic parameters of frozen soil has been developed. The dynamic law of high temperature frozen soil under low confining pressure is studied, and the empirical formula of dynamic parameters of high temperature frozen soil under certain conditions is given, which has reference value for seismic design of subgrade engineering. It is of great significance to ensure the safe operation of structures on the Qinghai-Xizang Plateau. This paper is based on the National key basic Research and Development Plan ("973" Plan), "performance Evaluation and Prediction of Frozen soil Engineering structures No. No.2012CB026104'". Taking the typical silty clay in Qinghai-Xizang Plateau as the research object, on the basis of summing up the present research situation at home and abroad, the field investigation and sampling, instrument development and laboratory test were carried out. The dynamic strength, dynamic shear modulus and damping ratio of high temperature frozen soil under low confining pressure are studied. The experimental results show the influence of different factors on the dynamic parameters of high temperature frozen soil. It provides more suitable parameters for seismic design of structures in high-temperature frozen soil area, and verifies the applicability of the new test instrument. The main results include the following aspects: 1) on the basis of summarizing and analyzing the present research situation at home and abroad, the paper points out the deficiency of the present research, and points out that the dynamic characteristics of the high-temperature frozen soil under low confining pressure are lack of systematic research, and this is the emphasis of the research. 2) through the field investigation, the typical site is selected and monitored, and the related indoor geotechnical test is carried out to master the basic soil properties of the soil sample. It lays a foundation for further study on the dynamic properties of silty clay in Qinghai-Xizang Plateau. The development process of each component of the direct shear test system for frozen earth dynamic load and the determination of related parameters are given. The hydraulic power system of the instrument and the controlled temperature direct shear box are analyzed respectively. The design of the joint of actuator and working platform is carried out, and the accuracy and applicability of the new instrument are preliminarily verified by the temperature control effect test and the dynamic direct shear test under different conditions. (4) based on the dynamic strength theory of the soil, a series of dynamic triaxial shear tests under different temperature, confining pressure and vibration times are carried out. The dynamic strength parameters of soil under different conditions are obtained, and the influence of temperature and vibration times on the dynamic strength is analyzed, and the similarities and differences between the two test methods and the test results are compared and analyzed. 5) through summarizing the constitutive relation of soil dynamics, combining the dynamic triaxial test and the dynamic direct shear test, the experimental results are obtained. The Hardin-Drnevich dynamic constitutive model was used to study the experimental results. The influence of temperature, confining pressure and vibration times on the dynamic parameters was systematically analyzed. The similarities and differences of the two test methods in determining the dynamic shear modulus and damping ratio are compared and analyzed, which further verifies the applicability of the new test instrument.
【学位授予单位】：北京交通大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TU445

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