综合物探方法在浙江软土地区城市深埋管线探测中的案例剖析与方法研究

Case analysis and study of comprehensive geophysical methods in urban deep buried pipeline detection in soft soil regions of Zhejiang province

随着非开挖技术的广泛应用,使得城市深埋管线的精细化探测难题尤为突出。特别是在软土、地下水丰富的城区,传统的地面管线探测技术在探测深埋管线时本身存在的抗干扰能力弱、信噪比低、探测深度不足等问题进一步放大,往往无法取得良好的探测效果。笔者以井中磁梯度法、跨孔电阻率CT法、跨孔声波透射法等井中物探方法为主、常规的地面物探技术为辅,在浙江软土地区开展了大量的、不同类型的深埋管线探测研究工作,取得了一些认识:(1)井中磁梯度法和跨孔超声波法,均能准确识别出深埋管线的平面位置及埋深,精度可达几厘米;(2)井中磁梯度法仅对深埋的磁性金属管线有效;(3)跨孔声波透射法能适应各种材质的深埋管线,但对跨孔距离有一定要求,一般在软土地区要孔间距小于8 m效果更佳;(4)跨孔电阻率CT法对孔间距要求相对较低,但是该方法存在体积效应问题,电阻率异常往往大于目标体本身,探测分辨率相对较低。考虑到城市浅表地区为人类扰动层,各种干扰较多,为了消除物探技术的多解性,建议条件允许的情况下,采用两种以上的井中物探技术进行探测、互相验证,可得到更可靠、更精细的探测效果。

With the wide application of trenchless technology,the problem of fine detection of urban deep-buried pipelines is particularly prominent.Especially in urban areas rich in soft soil and underground water,the traditional ground pipeline detection technology has weak anti-interference ability,low signal-to-noise ratio,insufficient detection depth,and other problems when detecting deep buried pipelines,and often fails to achieve good detection results.In this study,the borehole magnetic gradient method,cross-hole resistivity CT method,cross-hole acoustic transmission method,and other borehole geophysical prospecting methods are mainly used,and the conventional ground geophysical prospecting technology is supplemented.Many different types of deep buried pipeline detection research have been carried out in the soft soil area of Zhejiang Province.Some understanding has been obtained:the borehole magnetic gradient method and cross-hole ultrasonic method can accurately identify the plane position and buried depth of the deep-buried pipeline,with the accuracy of several centimeters.The borehole magnetic gradient method is only effective for deep-buried magnetic metal pipelines.The cross-hole acoustic transmission method can adapt to the deep-buried pipelines of various materials,but it has specific requirements for the cross-hole distance.Generally,the effect is better if the hole spacing is less than 8m in soft soil areas.The cross-hole resistivity CT method has relatively low requirements for hole spacing,but this method has the problem of volume effect.The resistivity anomaly is often more significant than the target body,and the detection resolution is relatively low.Considering that the urban shallow area is a human disturbance layer and there are many kinds of interferences,in order to eliminate the multi-solution of geophysical prospecting technology,it is recommended to use more than two kinds of borehole geophysical prospecting technology to detect and verify each other when conditions permit,to obtain more reliable and precise detection results.