基于新型BOTDR原理边坡变形特性及失稳机理分析研究

Distributed, real-time remote, early and accurately determine the status of rock and soil anomaly is the difficulty of geological disaster monitoring. Two projects were granted by the National Natural Science Foundation, we have successfully designed a combined optical fiber transducer, which has higher initial precision, larger measuring sliding distance and dynamic range, and it can also determine the direction of movement of the load at the same time. However, evidence in our previous studies showed that: The current BOTDR instrument is noise, low spatial resolution, which greatly restricted the establishment of a new monitoring system based on our novel combined optical fiber transducer. Therefore, we aim to improve the BOTDR based on the novel BOTDR principle. Through the first pulse slice method, combined with the improved generalized harmonic Wavelet algorithm for fitting mathematical models and establishing the parameters to make the novel BOTDR have lower noise, better algorithms and higher spatial resolution. Then we can more accurately measure the landslide displacement and shearing zone. These will develop the fiber optical sensing technology platform. Also, we will carry out serial tests on grouting piece which installed with combined optical fiber transducer, so do the indoor model direct shearing tests and in-site field tests. Therefore, the technical indicators and the suitable using conditions of the improved BOTDR will be explored, the coupling matching relationship between the combined optical fiber transducer and the grouting material will be verified, the coupling matching relationship between the fiber loss and the sliding distance will be formed. Then, a comprehensive early warning system of slope deformation, the direction of movement and real-time long distance monitoring will be established. Thus, a new explanation for the slope failure mechanism can be presented.

分布式、实时远程、早期准确判断岩土体异常状态是地质灾害监测的难点。项目组在2项国家自然科学基金资助下，成功研制具有初始高精度、较大测量行程和动态范围，可判断运动方向的复合光纤装置。但在研究中发现：目前的BOTDR仪因原理限制而噪声大、空间分辨率低，极大制约了新型复合光纤监测体系的建立。因此，申请人拟基于新型BOTDR原理改进BOTDR仪，通过首创的脉冲条分法、并联合改进型广义谐波小波算法拟合数学模型，建立参数，使其具有噪声更低、算法更优和更高空间分辨率，据此更加准确地探明滑坡体的位移量、滑移面位置，扩展光纤传感技术运用平台。并开展基于复合光纤装置的灌浆体、室内模型直剪试验和现场原位监测，探索该改进BOTDR仪的技术指标和适用条件，验证复合光纤装置与灌浆材料间的耦合匹配关系，建立光纤损耗与滑动面滑移量的耦合关系，构建边坡变形及运动方向远程、实时监测的综合预警体系，为边坡失稳机理提供新的解释。

项目组研制了新一代复合光纤装置、基于强光栅和超弱光栅的三类、四种传感器，传感器均可用于边坡稳定的实时、远程、高精度监测；同时，第一代基于超弱光栅的传感器还表现出了用于隧道、大坝以及桥梁等结构的优势和特点。联合校外公司研制了超弱光栅分析仪样机，目前应变精度为不大于5 με，温度精度为不大于0.5℃，空间分辨率为不大于5米，测量长度不低于5公里。研制了与本项目相匹配的新型复合光纤装置直剪仪，为项目研究中室内直剪试验的开展提供了重要保障；复合光纤装置的直剪试验表明，该直剪仪不仅同时具有荷载测量，加载点位移记录和光纤行程更简便记录等功能，而且操作安全方便，且能较好地模拟双剪切滑移面工况，试验结果良好。进行了灌浆材料与复合光纤装置的耦合匹配研究，结果表明砂浆配比为1:5的EPS材质复合光纤装置效果最好。光纤损耗与滑移量之间满足多项式函数关系，为复合光纤装置滑坡预警模型的建立奠定了基础。自主研制了室内大型滑坡模型试验装置，主要由镀锌方钢构成，外包尺寸为4.7*2.2*1.7米，开展了3次室内大型滑坡模型试验、3次岩质、土质边坡现场监测、现场模型滑坡实验1次，结果表明，研发的传感器较好地完成了监测过程，应力、光纤损耗与位移反应滑坡演化的阶段性有良好的一致性，有蝴蝶结微弯调制的混联式复合光纤传感装置可对边坡滑移面位置实现较高精度的识别，从光学、应力变化的角度探讨了边坡滑移过程，以解释滑坡机理。此外，研究发现FBG应变传感器亦能较好的实现滑坡监测，将FBG应传感器与混联式复合光纤装置进行了较为全面的对比。超弱光栅与强光栅相比具有刻写密度大、价格便宜等诸多优点，课题组拟进一步研发新型超弱光栅传感器，以实现尽可能多的基础量的“集成式”监测，拓宽光纤光栅传感器的应用领域。.项目的研究不仅可以为边坡稳定的长期、远程监测提供成本不同、精度和效果不同的方案，而且研究成果还可以推广到隧道、大坝、桥梁等结构的健康监测，具有较大的工程意义和实际价值。