城际铁路岩溶综合勘察方法研究

Research on Comprehensive Karst Survey Method of Intercity Railway

灰岩地区岩溶发育情况对城际铁路的施工及安全运营有重要影响,因此针对性进行高精度地质勘察十分重要。为降低复杂城区环境的影响、提高城际铁路岩溶勘察的精度与效率,依托某城际铁路,通过理论与实际探测效果对比,统计分析实际探测溶洞的大小并对比分析200 m长度试验区域跨孔地震CT、钻孔、等值反磁通瞬变电磁法(OCTEM)与微动4种方法的岩溶探测效果,研究不同孔间距对跨孔地震CT的探测效果,跨孔地震CT探测溶洞的分辨率,特定区域跨孔地震CT波速解释原则以及OCTEM、微动在不具备开展跨孔地震CT条件时的勘察效果。研究结果表明,跨孔地震CT工作中15 m孔间距相对30 m孔间距原始数据质量更高,岩溶识别率、分辨率更高,岩溶发育规模、空间位置形态的确定更准确,后期施工注浆及注浆用量的估算更可靠;15 m孔间距跨孔地震CT能够对2 m以上的溶洞进行精准揭示;在特定区域可以根据地震波速大小,将灰岩地区岩溶发育情况定量解释为风化层、溶蚀裂隙、溶洞以及较完整灰岩;在不具备跨孔地震CT工作条件时开展OCTEM和微动进行补充勘察,可以探明较大的溶洞,定性查明灰岩地区岩溶发育的程度。勘察方法具有勘察精度高以及不易受城际铁路沿线环境影响的特点,对城际铁路工程岩溶勘察具有重要意义,可在其他城际铁路岩溶勘察中推广使用。

Karst has an important impact on the safe construction and operation of tunnels in the intercity railway survey in limestone areas.Therefore targeted high-precision geological exploration is very important.In order to reduce the impact of complex urban environments and improve the accuracy and efficiency of intercity railway karst exploration,statistical analysis is conducted on the size of actual karst caves detected,and the karst detection effects of four methods including cross hole seismic CT,drilling,opposing coils transient electromagnetics method(OCTEM),and microtremor exploration in a 200 m long experimental area are compared and analyzed based on the comparison of theoretical and practical detection effects of a certain intercity railway.The detection effects of different hole spacing on cross hole seismic CT are studied,the resolution of cross hole seismic CT detecting karst caves,the principles for interpreting the velocity of cross hole seismic CT in specific areas,and the exploration effects of OCTEM and microtremor exploration in the absence of conditions for conducting cross hole seismic CT are studied.The research results indicate that in cross hole seismic CT work,the quality of the original data with a 15 m hole spacing is higher than that with a 30 m hole spacing,and the karst identification rate and resolution are higher.The determination of the scale and spatial location of karst development is more accurate,and the estimation of grouting and grouting dosage in later construction is more reliable.Cross hole seismic CT with a spacing of 15 m can accurately reveal karst caves above 2 m.In specific areas,the development of karst in limestone areas can be quantitatively explained as weathering layers,dissolution cracks,karst caves,and relatively complete limestone based on the magnitude of seismic wave velocity.When cross hole seismic CT working conditions are not available,conducting OCTEM and micro motion supplementary surveys can identify larger karst caves and qualitatively determine the degree of karst development in limestone areas.The survey method has the characteristics of high survey accuracy and is not easily affected by the environment along the intercity railway.And it is of great significance for karst survey of intercity railway engineering and can be promoted and used in other intercity railway karst surveys.