高密度电法在输电线路塔基基础附近多年冻土探测中的应用  

Application of high density electrical resistivity tomography in investigating the permafrost around tower foundations of power transmission line

作　　者：游艳辉 李党民 单波 田生祥 王新斌 俞祁浩 YOU Yanhui;LI Dangmin;SHAN Bo;TIAN Shengxiang;WANG Xinbin;YU Qihao(State Key Laboratory of Frozen Soil Engineering,Northwest Institute of Eco-Environment and Resources,Chinese Academy of Sciences,Lanzhou 730000,China;Northwest Electric Power Design Institute Co.,Ltd.of China Power Engineering Consulting Group,Xi’an 710075,China;State Grid Qinghai Electric Power Company,Xining 810008,China)

机构地区：[1]中国科学院西北生态环境资源研究院冻土工程国家重点实验室,甘肃兰州730000 [2]中国电力工程顾问集团西北电力设计院有限公司,陕西西安710075 [3]国网青海省电力公司,青海西宁810008

出　　处：《冰川冻土》2022年第2期684-692,共9页Journal of Glaciology and Geocryology

基　　金：国家自然科学基金项目(42071095);冻土工程国家重点实验室自主研究课题(SKLFSE-ZT-202106);中国电力工程顾问集团西北电力设计院有限公司科研项目(HQ-2018-P-TS-079)资助。

摘　　要：多年冻土区输电线路塔基基础附近活动层厚度和地下冰变化与基础稳定性密切相关,塔基施工的热扰动和混凝土基础的热效应使得基础周围冻土易发生退化,不利于基础的稳定。高密度电法是冻土工程环境研究中常用的地球物理方法,其探测结果的可靠性和分辨能力受数据采集方式、目标体地电结构影响。为减小对输电线路塔基附近冻土特征识别的不确定性,通过建立基础周围多年冻土地电模型的正反演模拟,发现活动层处于融化状态时各种装置方式数据采集均能较好地反映活动层厚度的起伏,但由于冻融锋面附近显著的电阻率差异,难以识别多年冻土层内的地下冰空间分布特征。而活动层处于冻结状态时进行探测能显著提高对多年冻土层内的地下冰空间分布特征识别精度,其中偶极-偶极装置可较好地识别高、低含冰量区域的发育位置和形态特征。在青藏直流输电线路塔基基础附近冻土探测中证实了方法的有效性,探测结果揭示了施工过程和基础热效应导致的塔基基础附近的地下冰退化。以上研究表明,通过正反演模拟,根据具体探测目标选择合适的探测时机和数据采集方式,能显著提高高密度电法探测结果的有效性和精度。Stability of foundations supporting power transmission lines in permafrost regions is closely related to the surrounding active layer thickness and ground ice variations. Thermal disturbance during the construction and heat effect of the concrete foundations tend to thaw the surrounding permafrost,endangering stability of the towers. The electrical resistivity tomography(ERT)method is frequently used in engineering and environmental research in permafrost regions. The reliability and limitation of ERT investigation are related to geoelectrical structures and array used for data collection. We reduced the uncertainty by forward and inverse modeling the geoelectrical models,which represent the permafrost around tower foundations. The results show that the active layer thickness can be effectively detected using different types of arrays,but the spatial distribution of ice-rich and ice-poor permafrost is barely identified when the active layer thaws out. The reliability of ground ice identification improves significantly if the ERT data are collected when the active layer is frozen. Under this condition,the dipole-dipole array shows a better ability to explore configurations of ice-poor and ice-rich permafrost. Effectiveness of the method was verified for tower foundations investigation in permafrost regions along QinghaiTibet Power Transmission Line. Degradation of ground ice due to the construction disturbance and heat effects of the concrete foundations were effectively identified. The results indicate that forward and inverse modelling can provide essential insights in designing experiment and collecting data. In this way,the reliability and resolution of ERT in investigating the permafrost characteristics can be significantly improved.

关 键 词：多年冻土 塔基基础 高密度电法 活动层厚度 地下冰 

分 类 号：P631[天文地球—地质矿产勘探] P642.14[天文地球—地质学]