跨孔雷达层析成像方法定量评价岩溶发育程度研究

贾龙; 张毅; 蒙彦; 李录娟; 潘宗源; 吴远斌; 殷仁朝

doi:10.11932/karst20250212

跨孔雷达层析成像方法定量评价岩溶发育程度研究

doi: 10.11932/karst20250212

贾龙^{1, 2,},
张毅³,
蒙彦^{1, 2},
李录娟^1, ,,
潘宗源^{1, 2},
吴远斌^{1, 2},
殷仁朝^{1, 2}

1.
中国地质科学院岩溶地质研究所/自然资源部、广西岩溶动力学重点实验室/联合国教科文组织国际岩溶研究中心, 广西桂林 541004
2.
中国地质调查局岩溶塌陷防治技术创新中心, 广西桂林 541004
3.
中铁二院工程集团有限责任公司, 四川成都 610036

基金项目: 广西重点研发计划项目《岩溶路基塌陷加筋垫层防控与光纤传感监测体系集成研发与应用示范》；中国地质调查局中国地质科学院基本科研业务费项目《岩溶塌陷大型物理模拟试验模型装置研发》（2021010）；中国地质调查局项目《岩溶塌陷地质灾害风险评价》

详细信息

作者简介:
贾龙（1985－），男，博士，副研究员，从事岩溶工程地质安全方面的研究。E-mail：jialong12@foxmail.com

通讯作者:
李录娟（1986－），女，副研究员，从事岩溶水工环方面的研究工作。E-mail：llujuan@mail.cgs.gov.cn。

中图分类号: P631；P642.25
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出版历程
- 收稿日期: 2024-03-30
- 录用日期: 2024-07-23
- 修回日期: 2024-05-04
- 刊出日期: 2025-04-20

Karst development evaluation based on cross-hole radar tomography

JIA Long^{1, 2
,},
ZHANG Yi³,
MENG Yan^{1, 2},
LI Lujuan^{1
, ,},
PAN Zongyuan^{1, 2},
WU Yuanbin^{1, 2},
YIN Renchao^{1, 2}

1.
Institute of Karst Geology, CAGS/Key Laboratory of Karst Dynamics, MNR & GZAR/International Research Centre on Karst under the Auspices of UNESCO, Guilin, Guangxi 541004, China
2.
Innovation Center of Karst Collapse Prevention Technology, China Geological Survey, Guilin,Guangxi 541004, China
3.
China Railway Second Institute Engineering Group Co., LTD., Chengdu,Sichuan 610036, China

摘要

摘要: 利用跨孔雷达走时层析成像和衰减层析成像技术实现钻孔之间地层岩溶发育程度的精细化定量评价，可弥补实际工程中钻探密度的限制。走时层析成像方法可得到岩溶地层中电磁波传输速度分布情况。因雷达波速是地层介电常数的函数，故可推导出岩溶地层的孔隙比，进而得到钻孔之间可溶岩的岩溶率的空间变化情况。衰减层析成像方法可得到岩溶地层中电磁波衰减系数分布情况。对于岩土这种低损耗材料，衰减系数与地层电导率成正比，与地层相对介电常数的平方根成反比，而岩溶地层电导率和相对介电常数与地层岩溶率密切相关，据此可量化钻孔之间岩溶率的空间变化情况。工程实例显示，两种方法得到的岩溶率空间分布结果一致，可相互印证精细评价钻孔之间不同埋深地层的岩溶发育程度，为地质勘察和工程建设提供更详实的数据支撑。
- 岩溶率 /
- 跨孔雷达 /
- 岩溶探测 /
- 岩溶发育评价
Abstract: Cross-hole geo-radar tomography, which belongs to the method of electromagnetic wave tomography between boreholes, is a way of borehole radar detection. Specifically, electromagnetic waves are transmitted form one borehole (transmitting borehole) and the transmitted signals are received by another borehole (receiving borehole). The kinematic (travel time and ray path) and dynamical (waveform, amplitude, phase, and frequency) characteristics of these signals are recorded. By tomography technology, the influence of the medium between the boreholes on the singlals is analyzed to obtain the distribution of physical properties within the strata between the two boreholes, with the goal of inverting the internal structure of the medium. As a result, the geo-radar tomography method can identify underground structures that exhibit significant differences in physical properties, such as dielectric constant and conductivity. These underground structures include solitary rocks, fissures, caves, and other adverse geological phenomena, as well as buried public facilities. This technology can penetrate deep intosubsurface for detection through drilling boreholes, effectively isolating the interference from above ground and compensating for the limitations of drilling density in practical engineering.In geological field surveys, accurately determining true karstification rate of the soluble rock layers poses significant challenges. Consequently, the karstification rate along the drilling line is typically employed as a representation measure, which has inherent limitations. To enhance the quantitative analysis of karst development within strata, this study employs cross-hole geo-radar tomography technology to process radar transmission data. This approach allows for the calculation of numerical changes in karstification rates, facilitating a more precise quantitative evaluation of the degree of karst development between boreholes.In karst areas, the materials filling karst fissures—such as including air, water, and loose soil—are the primary factors contributing to variations in the dielectric constant of rock masses. The velocities of radar waves are a function of the dielectric constant of the geological strata. By measuring the transmission velocities of electromagnetic waves in karst strata through cross-hole geo-radar, the porosity of limestone can be determined, allowing for the assessment of variations in the karstification rate between boreholes. The cross-hole geo-radar tomography method can provide insights into the distribution of transmission velocities of electromagnetic waves in karst strata, and thereby revealing the spatial variations in the karstification rates of soluble rocks between boreholes.When electromagnetic waves propagate in karst strata, their amplitudes exhibit exponential attenuation. In karst areas, the materials filling in karst fissures are also the main factors contributing to variations in electromagnetic wave attenuation. The cross-hole geo-radar tomography method can obtain the distribution of attenuation coefficients of electromagnetic waves in karst strata. For low-loss materials such as rock and soil, the attenuation coefficient is directly proportional to the conductivity of strata and inversely proportional to the square root of the relative dielectric constant of strata. Moreover, the conductivity and the relative dielectric constant of karst strata are closely related to the karstification rates of strata. Based on this, the spatial variations of karstification rates between boreholes can be quantified.Engineering examples demonstrate that, based on the physical parameters—wave velocity and attenuation coefficient—derived from the cross-hole geo-radar travel time tomography and attenuation tomography, as well as the distribution of karstification rates, it is feasible to map the distribution of karst development between boreholes. At a burial depth of 28 m to 32 m, it is inferred that karst caves are filled with flowing–soft plastic saturated clay and are likely to span the strata between the two boreholes. At a burial depth of 37 m to 41 m, it is presumed that karst caves are filled with plastic saturated clay. The spatial results of karstification rates obtained from both methods are consistent and mutually corroborative, providing a refined quantitative evaluation of the degree of karst development in strata at varying burial depths between boreholes. This provide more detailed data support for geological surveys and engineering construction. In addition, the accurately determining the karstification rates of strata based on wave velocity and attenuation of the cross-hole geo-radar requires precise values of all physical parameters of strata. These parameters can be obtained through laboratory tests on rock cores.Theoretical analysis and on-site testing demonstrate that the application of cross-hole geo-radar travel time tomography and attenuation tomography techniques can achieve a precise quantitative evaluation of the karst development degree in the strata between boreholes, thereby obtaining the inter-borehole "surface" karstification rates. This will provide more detailed data for karst geological surveys. In addition, considering the multisolution nature of geophysical survey results and the complexity of karst geology, it is recommended to combine these techniques with imaging detection of borehole radar reflection and other geophysical methods during actual detection.
- karstification rate /
- cross-hole geo-radar /
- karst detection /
- evaluation of karst development

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图 1 跨孔地质雷达探测原理示意图

A．地质模型 B.层析成像模型，红色的区域为低速区或高衰减区，蓝色区域为高速区或低衰减区

Figure 1. Schematic diagram of cross-hole geo-radar

A. Geological model B. Tomography model, the red area represents the low-speed or high attenuation zone, and the blue area represents the high-speed or low attenuation zone

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图 2 探测所用仪器设备和软件

A. ProEx雷达主机 B.100 Mhz孔中雷达天线 C.采集软件GroundVision D.数据处理软件WinTomo

Figure 2. Instruments and software of cross-hole geo-radar

A. ProEx radar host B.100 MHz hole radar antenna C. Acquisition software GroundVision D. Data processing software WinTomo

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图 3 基于跨孔雷达层析成像的钻孔剖面岩溶发育评价图（ZK1-ZK3）

A.波速分布图 B.衰减分布图 C.波速计算岩溶率图 D.衰减计算岩溶率图

Figure 3. Karst development evaluation of borehole profile based on cross-hole geo-radar tomography (ZK1–ZK3)

A. Wave velocity distribution diagram B. Attenuation distribution diagram C. Wave velocity calculation karst rate diagram D. Attenuation calculation karst rate diagram

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图 4 发射孔ZK1和接收孔ZK3之间地层解译图

1.灰岩 2.粉质黏土 3.流-软塑状粉质黏土 4.可塑状粉质黏土

Figure 4. Interpretation diagram of the strata between transmitting hole ZK1 and receiving hole ZK3

1. Limestone 2. Silty clay 3. Flow soft plastic silty clay 4. Plastic silty clay

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表 1 研究区地层的电性参数

Table 1. Electrical parameters of the strata in the study area

介质	相对介电常数	电导率/s·m⁻¹	传播速度/m·μs⁻¹	衰减系数/dB·m⁻¹	衰减系数/np·m⁻¹
空气	1	0	300	0	0
岩溶水	81	0.05	33	0.1	0.0115
干石灰岩	7	10⁻⁸~10⁻⁶	113	0.4	0.0460
湿石灰岩	8	0.018	106	0.4~1	0.046~0.1151
饱和黏土	15	0.08	60~90	1~300	0.1151~34.5383

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表 2 测孔信息表

Table 2. Table of borehole information

	深度/m	岩土特征
发射孔 ZK1	26.3	覆盖土层：填筑土（0~1.5 m），粉质黏土
	27.5	中风化石灰岩：青灰色，隐晶质结构，中厚层构造，节理裂隙发育
	30.5	溶洞：全填充，黄褐色，充填物为粉质黏土及碎石，粉质黏土呈可塑状
	40.5	中风化石灰者：青灰色，隐晶质结构，中厚层构造，节理裂隙发育
接收孔 ZK3	28.7	覆盖土层：填筑土（0~1.7 m），粉质黏土
	28.8	中风化石灰岩：青灰色；隐晶质结构，中厚层构造，节理裂隙发育，岩芯呈柱状
	30.1	溶洞：全充填，棕红色，充填为粉质黏土，可塑
	31.3	中风化石灰岩：青灰色，隐晶质结构，中厚层构造，节理裂隙发育
	31.9	溶洞：半充填，黄褐色，充填物为粉质黏土，流—软塑状
	45.5	中风化石灰岩：青灰色，隐晶质结构，中厚层构造，节理裂隙发育

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