Horizontal directional drilling technology combines traditional geological survey core technology with horizontal directional drilling technology, supplemented by in-hole testing technology, which can intuitively and accurately understand the adverse geological conditions in front of the tunnel head. At present, this technology has been applied in the geological survey of tunnels at home and abroad, but it also has disadvantages such as affecting the tunnel construction technology, the inability to predict some small faults and large penetrating joints, and the difficulty in drilling broken rock masses.
Horizontal directional drilling technology originated in the petroleum drilling industry and is widely used in the construction of municipal pipelines and oil and gas pipelines. The world’s first horizontal directional drilling pipeline laying project appeared in 1971. In 1988, the rock-stratum horizontal directional drilling pipeline crossing construction was successfully realized for the first time. Horizontal directional drilling technology combines traditional geological survey core technology with horizontal directional drilling technology, supplemented by in-hole testing technology, which can intuitively and accurately understand the adverse geological conditions in front of the tunnel head.
At present, the horizontal directional drilling technology of foreign rock formations has been applied in site survey, steering trajectory design, steering hole excavation, steering method and drilling equipment. China introduced horizontal directional drilling technology late, and in recent years it has been rapidly improved in theoretical research and equipment research and development, and domestic horizontal directional drilling rigs have reached the advanced level of foreign countries.
The application of horizontal directional drilling technology in tunnel engineering is to drill a horizontal survey hole parallel to the design axis of the tunnel, and carry out coring, hydraulic fracturing, comprehensive logging and intra-hole television and other related tests in the hole, using comprehensive testing methods It can accurately divide the lithological changes of the surrounding rock on the design axis of the tunnel, the distribution range of the fracture zone, and the water inrush condition of the tunnel, so as to realize the geological prediction of the surrounding rock of the tunnel. The technology mainly includes five core technologies: drilling, coring, steering, measurement while drilling, and comprehensive logging.
(1) Drilling technology. Horizontal directional drilling is mainly based on comprehensive drilling, and the specific coring interval is determined according to the geological design and working conditions. The comprehensive drilling is mainly based on the bottom hole power (screw drilling tool) driven roller bit compound drilling. For extremely hard formations, use the “turbodrilling tool to drive diamond bit” compound drilling, using the high speed characteristics of the turbodrilling tool for efficient rock fragmentation; or using the “screw drill + hydraulic hammer” two-in-one compound drilling to increase impact Load, improve the efficiency of rock fragmentation.
(2) Coring technology. The coring technology can be divided into rope coring and drilling core. Rope coring means that when the core is filled with the inner pipe, the inner pipe is taken out from the drill pipe with a rope salvage device without lifting the drill to obtain the core. Rope coring is widely used because of its significant advantages such as high drilling efficiency, high core adoption rate, low labor intensity, and low drilling cost. When the drill bit reaches the core point, all the drilling tools in the hole are completely lifted out, replaced with core drilling tools, and drilled down for core drilling. After the core is completed, take out all the drilling tools in the hole again When it reaches the surface, it is replaced with a full directional drill bit to continue directional drilling, and so on, until all the coring plans are completed.
(3) Orientation technology. The horizontal directional drill obtains and adjusts the attitude angle information of the drilling tool in real time through the manual magnetic navigation directional drilling control system (wireless) and the measurement-while-drilling wired steering system, including depth, dip, azimuth and tool face angle, etc., and can be based on These attitude and angle information control the forward direction of the drilling tool in real time, so as to ensure that the drilling tool is drilled and surveyed along the tunnel axis.
(4) Measurement while drilling technology. Measure near-bit parameter information through sensors: directional data (inclination angle, azimuth angle, tool face angle), formation characteristics (gamma ray, resistivity logging), drilling parameters (bottom hole pressure, torque, speed), etc. , Using the downhole transmitter to send the signal to the surface through the signal telemetry channel (hard wire method, electromagnetic wave method, drilling fluid pulse method) to achieve parameter measurement while drilling.
(5) Comprehensive logging. After each coring is completed, a hydraulic fracturing test is performed using the coring hole to measure the magnitude and direction of the in-situ stress. After the survey hole is drilled to the designed hole depth, the drill is lifted and installed without cable storage logging tools, and the lithology, hole temperature, density, permeability, and water content of the surrounding rock of the borehole are measured using sound waves, natural gamma rays, resistivity, etc. And other parameters for testing. It can also install battery-storing video detection equipment in the hole to determine the lithology in the hole.
Under complex geological conditions, the detection range and data accuracy of traditional tunnel advanced geological forecasting technology cannot meet construction safety requirements. Based on horizontal directional drilling technology, miniaturized drilling rigs can be used to carry out advanced geological prediction of horizontal directional drilling in the emergency parking area of tunnels, which supplements the technical limitations of traditional advanced geological predictions without affecting normal tunnel construction conditions.
Horizontal directional drilling technology can accurately survey the surrounding rock information of the tunnel in detail, which is mainly reflected in the following aspects:
(1) Establish the correlation between horizontal directional drilling parameters and the surrounding rock of the borehole, study the relationship between the rock breaking mechanism of the drill bit and the strength of the surrounding rock of the tunnel, and provide real and reliable data support for construction and excavation.
(2) Combining traditional geological investigation and coring technology with horizontal directional drilling technology to achieve intermittent coring, basic physical tests such as compressive strength of the core, detailed analysis of the basic physical characteristics of the lithology along the tunnel, and the surrounding rock of the tunnel Classification provides precise lithology parameters.
(3) The lithology of the surrounding rock in the horizontal survey hole is classified by means of water pressure to crack test, acoustic wave, natural gamma, resistivity, and in-hole television in the comprehensive logging technology, and the stress characteristics, Temperature, density, permeability, crack development degree, etc. are evaluated.
Horizontal directional drilling technology has a certain impact on tunnel construction:
(1) Drilling survey holes in the tunnel face can directly and accurately understand the geological conditions of the surrounding rock in front, but it will seriously affect the construction of the drill and blast tunnel, and it is difficult to adapt to the tunnel face operation of the TBM tunnel, which requires a long construction period. Working time seriously affects construction efficiency;
(2) Drilling survey holes parallel to the design axis of the tunnel in the cross passages of the tunnel, emergency parking lanes and other places has little impact on the tunnel construction.
At the same time, horizontal directional drilling technology also has certain limitations:
(1) The prediction effect is poor under complex geological conditions, and it is difficult to predict the small faults and large penetrating joints in front of the tunnel face, especially the structural plane parallel to the tunnel axis;
(2) It is easy to stick in the broken rock mass, the drilling operation speed is slow, and the risk of hole collapse is faced;
(3) The technologies of ultra-long-distance horizontal directional drilling, continuous coring, deep-buried geological high-precision drilling positioning system, and steering control still need further research.
In terms of technical economy, the economy of horizontal directional drilling technology is affected by comprehensive factors such as drilling conditions, geological conditions, equipment capabilities, footage speed, core requirements, field test and logging efficiency, and tunnel construction speed. By means of equipment selection and drilling plan optimization, the reasonable matching of drilling efficiency and construction cost can be realized.
In recent years, horizontal directional drilling technology has been researched and applied in the field of geological survey.
➤In 2013, the Xi’an Research Institute of China Coal Science and Industry Group completed a final hole diameter of 78.5mm and a final hole depth of 401.8mm in the gold mine of Taibai County, Baoji, Shaanxi, using a ZDY1000G full hydraulic high-speed drilling rig and a φ75mm tunnel rope core drilling tool. The on-site test of horizontal core drilling in China is the record of the depth of horizontal rope core drilling in China at that time;
➤In October 2019, during the exploration and drilling of the Chada tunnel on the Luolong section of the Sichuan-Tibet Railway, the Northwest Nonferrous Metals 713 team used the XDQ-1200 portable drilling rig of Shaanxi West Exploration Geological Equipment Co., Ltd. to carry out horizontal advanced geological forecast drilling operations, with a diameter of 75mm and a final The hole depth is 750.5m, setting the domestic depth record for horizontal drilling of portable drilling rigs.
➤On January 4, 2020, the Golden Diamond Company of Team 402 of the Sichuan Geological and Mineral Bureau successfully completed a 903.28m (75mm diameter) horizontal core drilling in a tunnel survey in the southwest, creating a record of similar drilling depths in domestic engineering surveys.
➤On May 30, 2020, Shaanxi Zhongke Trenchless Technology Co., Ltd. adopted horizontal directional drilling intermittent coring technology in the Tianshan Shengli Tunnel Project of Wuwei Expressway, and successfully extracted the core of Boa fault zone at 1900m, with the final hole level The drilling length is 2271m, setting a new record again.
➤Foreign countries, the Massachusetts Water Resources Administration (MWRA) used the directional core drilling system for the city’s 28.3km long subway water supply tunnel in the most complex geological part, using a 533m long borehole at a 30-degree angle from the ground. Bend the borehole to a horizontal position and take the core parallel to the top of the tunnel with a depth of 63m. The core is used to predict the geological conditions of the tunnel.
There are a large number of tunnels in the new section of the Sichuan-Tibet Railway from Ya’an to Linzhi, and the geological environment is complex, and the safety risks of tunnel construction are relatively high. Combining traditional geological survey core technology with horizontal directional drilling technology, supplemented by in-hole testing technology, can intuitively and accurately understand the adverse geological conditions in front of the tunnel face to a certain extent.
