光纤传感技术在边坡模型试验中的应用

 关于边坡模型的坡体变形监测较为困难，将光纤传感技术应用于边坡模型试验尝试解决这一问题。构建边坡模型进行人工降雨试验，采用光纤布里渊散射光时域反射测量技术(BOTDR)监测坡体变形和光纤光栅(FBG)传感技术监测坡面变形。将BOTDR光纤分层埋入坡体不同位置，以边坡后缘模型箱为固定的参照点，监测坡体内不同位置的应变变化；将光纤光栅传感器铺设在坡面的不同位置，以坡面后缘为固定参照点，监测坡面各位置处位移变化。根据降雨前、降雨过程中及降雨后变形记录资料，得到边坡在降雨作用下的变形规律：在降雨初始一段时间内，边坡并没有明显变形，随着降雨时间的发展，坡体和坡面位移会出现突发性的大幅度增长，并且距坡面较近的土体产生较大的变形，坡体底部变形较小。总体规律是随着坡体深度的增大，坡体变形受降雨入渗的影响越来越不明显，这解释了降雨诱发的均质土坡破坏容易出现在浅层的原因。在坡面上，后缘产生较大位移，而坡体前端位移较小。降雨停止后，部分变形值会变小。试验结果表明，用光纤BOTDR和FBG传感技术监测有众多的优点，且光纤传感技术在岩土模型试验中具有良好的应用价值和前景。

APPLICATION OF OPTICAL FIBER SENSING TECHNOLOGY TO SLOPE MODEL TEST

It is relatively difficult to monitor the deformation of slope body in model test. To solve this problem，the optical fiber sensing technique is applied to slope model test. By constructing physical model for slope under artificial rainfall，the deformation in slope body can be monitored by optical fiber sensing technology of Brillouin optical time domain reflectometer(BOTDR)；and the deformation on slope surface can be monitored by fiber Bragg grating(FBG). Regarding the fixed point on the model box as the reference point，the variations in slope body can be monitored by the optical fiber preburied in the different locations of slope；and the deformation on slope surface can be achieved by the FBG sensor set on the slope surface. According to the recorded data of deformations before，during and after rainfalls，it can be found that the deformation of slope is not obvious in initial period of rainfall，but as the time goes on，there is a sudden growth of the deformation in the slope body and surface. The part of the slope closer to the surface has the larger deformation，but the part at the bottom of the slope has the least deformation. The overall law is that the influence of rainfall on slope body diminishes gradually with increase of depth of slope body. That can explain why the homogeneous soil-slope¢s failure induced by rainfall is easy to occur in shallow strata. In the slope surface，the maximum deformation appears in the trailing edge of slope，and the minimum one appears in the front edge. After the rainfall，a part of the deformations in the slope reduces to a lower value. The experimental result has proven that the optical fiber sensing technologies of BOTDR and FBG have many advantages in the monitoring of geotechnical engineering，and they can offer practical references and prospects on application.