为解决在地面环境复杂的城市建筑密集区域往往无法采用传统的竖向勘探手段进行工程地质勘察的问题，引入在地质、煤炭、石油等行业已较为成熟的定向钻探技术，沿地下工程轴线布设长距离的定向钻孔，在重要地质点处采用分支钻孔，通过沿设定轨迹间隔取芯的方式，在钻孔内实施特定的随钻测量及综合测井，以了解地下工程区域的地层岩性、地质构造，并准确确定围岩性质以及掘进和支护所需的地层参数。基于广州城区成功实施的660 m主孔+2条330 m分支孔可控轨迹钻探工作，采用提钻取芯的方式间隔15~30 m取芯，辅以孔内声波、电阻率测试，并将钻探芯样与物探成果相互印证，可详细探察隧道洞身一定范围内的工程地质条件。
The traditional vertical geological survey is often
impractical in urban areas with dense buildings and complex surface
environments. Therefore, directional drilling technology, which has already
reached a relatively high level of maturity in geology, coal mining, and oil extraction,
is introduced. Longdistance directional drilling is
arranged along the underground engineering axis in this approach, explicitly
using lateral hole drilling at critical geological points, and core samples at
regular intervals are extracted. The specific measurement is obtained while
drilling and comprehensive geophysical exploration is conducted in the drilling
hole along the set trajectory to understand the formation lithology and
geological structure of underground engineering area. Consequently, the
surrounding rock lithology and tunneling and supporting parameters are
determined. Based on the successful implementation of controlled track drilling
for a 660 m mainhole and two
330 m lateral holes in Guangzhou urban area, the core drilling at an interval
of 15~30 m is implemented and borehole acoustic wave and resistivity tests are
used as supplements. Finally, the drilling core samples are compared with the
results obtained through geophysical exploration to comprehensively assess the
engineering geological conditions within a certain range of the tunnel.
