三维随机裂隙介质建模与GPR响应计算

Modeling of 3D stochastic fracture media and calculation of GPR response

岩土中各成分的涨缩性差异会使局部位置产生有规律的裂隙结构,并形成软弱带。在降雨、渗流等水文因素的影响下,滑坡体一般会沿着软弱面或软弱带,整体地或分散地顺坡向下滑动,因此这些软弱带的探测是一个急需解决的重要的问题。这里提出了一种以三维Koch分形曲线来模拟不同含水率裂隙带的建模方法,建立了一个三层岩土背景下的倾斜裂隙带模型,裂隙带具有不同的含水率。在探地雷达(GPR)数值模拟的基础上,定性分析发现裂隙带含水率对响应波形的影响较大,含水率较高时裂隙带波形会与背景分界面混杂。对响应进行S变换(ST)后,根据时频特性既可抑制混杂波形,又可定量计算裂隙带响应与含水率的关系,最后进行了裂隙带深度的误差分析。此建模、探地雷达响应数值模拟及信号时频分析方法,可以为岩土体中软弱带及含水裂隙带的探测提供参考。

The difference of swell-shrink characteristic of soil constituent can produce a regular fracture structure in the local location,which is the weak belt in the soil.Under the influence of hydrological factors such as rainfall and seepage,the landslide will generally slide down along the weak surface or the weak belt,as a whole or dispersions.The detection of weak belt is an important issue.In this paper,a modeling method basing on three-dimensional Koch fractal curve is proposed to simulate the real fissure.The detailed process includes that the application of the generalized energy minimization principle to determine the Koch curve turning point,the control of fracture's morphology and position,then use the stochastic equivalent medium as the model of the soil background.Using the above modeling method,a model of tilted fracture belt in a three-layer soil background is established,and different water content is given to the fracture belt.Based on the numerical simulation of GPR,the influence of water content on the waveform response is analyzed qualitatively.When the water content is high,the fissure belt's waveform will be mixed with the background interface Finally,the noise is suppressed by S transform(ST),and the relationship between the water content and response is calculated quantitatively according to its time-frequency characteristic,and the error analysis of the fissure belt depth is carried out.This modeling,numerical simulation and time-frequency analysis method can help the detection of soft belt and water-bearing fractured belt in soil.