侧限条件下红砂岩土在循环冲击作用下的动态响应特性

发布时间：2018-03-01 16:27

本文关键词： 红砂岩土动静组合试验力学特性能量消耗数值模拟　出处：《江西理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：由于红砂岩土在我国分布较为广泛,赣南地区山地表层存在着大量的红砂岩风化土,红砂岩填土地基作为现代岩土工程中一种比较广泛使用的地基形式,在施工的过程中对其冲击加固及后期使用中偶然荷载的扰动都将对土的动态力学特性产生很大的影响,但目前对于土体在这种冲击荷载作用下所产生的作用效应以及地基土的能量消耗等问题研究不足。就此本文采用试验与数值模拟相结合的方法,研究具有侧限的红砂岩土在循环冲击作用下的动态响应特性,得到如下主要结论:(1)随着循环冲击次数的增加,比能量吸收值呈S递增型变化,土体所获得的吸收能用来挤压土中的气体和液体以及土体颗粒间的孔隙,使其土颗粒重新排列,内部结构重新分布,增强了红砂岩土体抵抗外界冲击力;干密度对红砂岩土比能量吸收值影响较大;当轴压不变时,冲击荷载与比能量吸收值呈正相关;当冲击荷载不变时,轴压与比能量吸收值呈负相关。(2)随着冲击次数的增加,红砂岩土体所获得的累计吸收能不断增加,且随着干密度的增加累计吸收能的增长速度越快,即曲线越陡;并对累计吸收能的相关系数进行数据拟合,从而可以计算出该干密度下红砂岩土在某循环冲击次数下所对应的累计吸收能;利用相同的分析方法,可计算出红砂岩土在不同轴压和冲击荷载下的累计吸收能,通过累计吸收能的大小可以大致得知土体在循环冲击荷载作用下的加固程度,为工程实际提供相关数据。(3)动态压缩强度和平均应变率呈负相关,且随着平均应变率的增大,无论是轴压还是冲击荷载的增大,动态压缩强度均在减小且逐渐“靠拢”;循环冲击过程中,随着冲击次数的增加,峰值应力在逐渐增大,呈S递增型曲线,而平均应变率在逐渐减小,呈S递减型曲线。(4)借助大型通用有限元程序输出的应力与位移的大小,根据应力、红砂岩土试样体积变化量与能量之间的关系,通过人工编程积分,得到红砂岩土在冲击荷载作用下,吸收的能量大小,与试验结果比较接近。对于以后研究此类问题时,可以借助有限元程序模拟红砂岩土在高应变率下的动态力学特性及能量的吸收与传递规律。本文利用动静组合加载装置,得到红砂岩土在循环冲击荷载作用下的力学特性参数,丰富了红砂岩土在动荷载作用下能量传播理论,综合对比分析红砂岩土能量耗散规律,为后续红砂岩土在循环冲击荷载作用下的加固研究做铺垫。
[Abstract]:Because the red sandstone soil is widely distributed in China, Gannan mountain has a large number of red sandstone surface weathering red sandstone soil filling foundation as a modern geotechnical engineering in a widely used form of foundation, reinforcement of the impact in the process of construction and using period of disturbance in accidental load will be dynamic the characteristics of soil have a great impact, but the effect of soil in the foundation soil under impact load and energy consumption problems such as insufficient research. This paper adopts the combination of test and numerical simulation method, the dynamic response characteristics of red sandstone soil confined in the cycle under impact the main conclusions are as follows: (1) with the increase of cycle number of the impact energy absorption value is S, than the incremental changes, the soil absorption can be used to squeeze gas in soil and The liquid and soil particles pore, the soil particles rearrange, the internal structure of re distribution, enhance the red sandstone soil resistance to external impact force; dry density absorption value has a great influence on red sandstone soil energy; when the axial pressure is constant, the impact load and energy absorption values were positively correlated; when the impact load is constant, shaft pressure and specific energy absorption value was negatively correlated. (2) with the increase of impact times, the cumulative energy absorption of red sandstone soil was increased, with the increase of the dry density and total absorbed energy will grow faster, the curve is steep; and the data fitting of the correlation coefficient of total absorption energy, thus can calculate the dry red sandstone soil density corresponding to a number of cyclic impacts the total absorbed energy; using the same analysis method, which can calculate the red sandstone soil under different axial pressure and the total absorbed energy under impact load, The total absorbed energy can be roughly the size of that level in the circulation of soil reinforcement under impact load, and provide the relevant data for the engineering practice. (3) the dynamic compressive strength and average strain rate was negatively correlated, and with the increase of average strain rate, both the axial pressure or increase hammer load, dynamic compressive strength in the "close" and decreased gradually; circulation in the process of impact, with the increase of impact times, the peak stress increases gradually, in increments of S curve, and the average strain rate gradually decreases, a S decline curve. (4) by the large general-purpose finite element program output stress and displacement according to the stress, and the relationship between the amount of energy and volume change of soil specimens of red sandstone, through artificial integral programming, get the red sandstone soil under impact load, the size of the energy absorption, close comparison with test results. For the future research in this Such problems, dynamic mechanical properties and energy absorption and transfer laws can be simulated by the finite element program of red sandstone soil under high strain rate. The dynamic loading device, obtained parameters of mechanical properties of red sandstone soil under cyclical impact loadings. The rich red sandstone soil under dynamic loading energy transmission the theory of comprehensive comparative analysis of red sandstone soil energy dissipation law, for the follow-up of red sandstone soil under cyclical impact loadings. The consolidation of the groundwork.

【学位授予单位】：江西理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU41

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