冲击荷载作用下红砂岩土的力学性质及能量耗散规律研究

发布时间：2018-06-22 14:23

本文选题：数值模拟 + 红砂岩土　；参考：《江西理工大学》2017年硕士论文

【摘要】：红砂岩土是一种广泛存在于南方地区的泥质胶结状土,红砂岩土在静态方面和准静态方面的研究已经比较深入,但是在动态冲击方面的力学性质及其能量耗散规律研究尚浅。本文采用冲击加载试验与数值模拟相结合的方法,研究了红砂岩土在单轴冲击、侧限条件下冲击和动静组合作用下冲击三种情形下的的力学特性与能量耗散规律。在这三种情形下,研究了试样长径比、冲击速度对峰值应力的影响,研究了入射能、应变率、长径比和冲击速度对能量耗散规律的影响。主要包括以下内容:1,在单轴冲击数值模拟中,红砂岩土抗压强度较低,能量耗散效率也偏低。随着冲击速度的增加,其抗压强度增大,峰值应变增大;但峰值应力随试样长径比的增长而降低,峰值应变也减小,在这种情形下试样抗压强度较低,主要以剪切的形式破坏;运用数值模拟软件(ANSYS/LS-DYNA)进行模拟揭示出红砂岩土的能量耗散效率偏低,超过90%的入射能以反射波的形式消散。2,在侧限条件下,红砂岩土表现出比单轴状态更强的抗压强度,能量耗散效率稍有提高;通过数值模拟得到与试验一致的结论。红砂岩土在套管的约束下,随着冲击速度的增长,峰值应力增长显著,峰值应变明显增加;在施加套管后,试样不再破坏,然而套管对能量耗散效率的提升仍很微弱,仍有接近90%的入射能以反射结束。3,在动静组合作用下,红砂岩土表现出很强的抗压强度,能量耗散效率显著提升,数值模拟得到与试验一致的结论。在0.5MPa的轴压下,峰值应力和峰值应变随冲击速度的增长成倍数增长,随长径比的增长成下降趋势。随着冲击速度的增长,反射能逐渐减小,有接近50%的入射能转化为透射能和耗散能;随着长径比的增长,耗散能在增长,效率却在降低。4,轴压能够提高红砂岩土的抗压强度和能量耗散效率,增大轴压的数值,效果更加显著。
[Abstract]:Red sandstone soil is a kind of muddy cemented soil widely existing in southern China. The research on static and quasi static aspects of red sandstone soil has been carried out deeply, but the mechanical properties and energy dissipation law of red sandstone soil in dynamic impact are still shallow. In this paper, the mechanical properties and energy dissipation of red sandstone soil under uniaxial impact, lateral limit impact and dynamic combination are studied by means of impact loading test and numerical simulation. In these three cases, the effects of aspect ratio and impact velocity on peak stress are studied, and the effects of incident energy, strain rate, aspect ratio and impact velocity on energy dissipation are studied. In the uniaxial impact numerical simulation, the compressive strength of red sandstone soil is low and the energy dissipation efficiency is low. With the increase of the impact velocity, the compressive strength increases and the peak strain increases, but the peak stress decreases with the increase of the aspect ratio, and the peak strain also decreases. In this case, the compressive strength of the specimen is lower and the specimen is destroyed mainly in the form of shear. Numerical simulation software (ANSYS- LS-DYNA) shows that the energy dissipation efficiency of red sandstone soil is low, over 90% of the incident energy dissipates in the form of reflected waves. Under the lateral limit condition, the red sandstone soil exhibits a stronger compressive strength than the uniaxial state. The energy dissipation efficiency is improved slightly, and the numerical simulation results are in agreement with the experimental results. Under the constraint of casing, the peak stress and peak strain of red sandstone soil increase significantly with the increase of impact velocity. After the casing is applied, the specimen is no longer destroyed, but the increase of casing energy dissipation efficiency is still very weak. Nearly 90% of the incident energy ends with reflection. Under the combination of dynamic and static, the red sandstone soil exhibits strong compressive strength and energy dissipation efficiency. The numerical simulation results are in agreement with the experimental results. Under 0.5 MPA axial compression, the peak stress and strain increase exponentially with the increase of impact velocity, and decrease with the increase of aspect ratio. With the increase of impact velocity, the reflection energy decreases gradually, and nearly 50% of the incident energy is converted into transmission energy and dissipative energy, and with the increase of aspect ratio, the dissipative energy increases. The axial compression can increase the compressive strength and energy dissipation efficiency of red sandstone soil and increase the value of axial compression.
【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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