Fine stratum detection method suitable for deep tunnel surface pre-grouting construction

Abstract

The invention discloses a refined stratum detection method suitable for deep tunnel earth surface pre-grouting construction, which comprises the following steps of: firstly, selecting a drilling machine and a inclinometer while drilling, and constructing a drill hole; after the drill hole reaches the horizontal section of the tunnel treatment area, basic lithologic information of a stratum is obtained, coring operation is carried out in a segmented mode, and then a mechanical property test is carried out on a rock core sample; then a logging instrument is put down through the drill hole, and comprehensive logging is conducted; after comprehensive logging is completed, fracture distribution and hydrogeological conditions of a far-field area are detected through the detection instrument integration module; and finally, depicting complete geologic features of the tunnel excavation area. Various detection technologies such as hydraulic coring, comprehensive logging, water pressure monitoring, transient electromagnetism and geological radar are creatively integrated in a set drill hole, and key geological information such as stratum lithology, mechanical parameters, fracture development, hydrogeology and far-field anomalous bodies is actively and comprehensively obtained; the method overcomes the defects of one-sided information and insufficient accuracy due to the fact that geological conditions are indirectly deduced only by means of drilling tracks in a traditional method.

Description

Technical Field

[0001] This invention relates to the field of geological exploration technology. Specifically, it relates to a refined geological exploration method applicable to surface pre-grouting construction of deep tunnels. Background Technology

[0002] In the construction of deep-buried tunnels, grouting is a key technical means to ensure project safety and prevent geological disasters. The effectiveness of grouting depends crucially on the accuracy of determining the degree of fracture development and spatial distribution in the treated area. Currently, surface directional drilling, as the mainstream method of geological exploration, suffers from limitations in methodology and analytical dimensions. It typically only obtains information from a single borehole, making it difficult to accurately determine the degree of fracture development and spatial distribution, which are decisive for the effectiveness of grouting. This problem is particularly pronounced in tunnels with depths reaching 1500m. The accuracy of grouting in such deep-buried tunnels highly depends on the accuracy of the exploration results. Failure to accurately determine fracture development and spatial distribution can easily lead to a lack of scientific basis for grouting design, resulting in grouting failure and safety hazards.

[0003] Analysis of existing technologies shows that current directional drilling-based exploration methods primarily focus on borehole layout and trajectory optimization. Their exploration capabilities heavily rely on the direct exposure of borehole trajectories. Effective analytical methods are lacking for the geological conditions of areas not directly encountered between branch boreholes, leading to insufficient understanding of the spatial distribution patterns of stratigraphic features. Therefore, it is urgent to overcome the limitations of existing exploration technologies to achieve precise exploration of stratigraphic fracture systems. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to provide a refined geological exploration method suitable for surface pre-grouting construction of deep tunnels. By integrating logging while drilling, core testing, cuttings logging, comprehensive logging, and instrument deployment during drilling of the horizontal section, the lithology, fracture development, and hydrological characteristics of the strata in the near and far fields are obtained, providing accurate geological information for grouting processing and realizing geological exploration of the tunnel excavation area.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0006] A refined geological exploration method applicable to surface pre-grouting construction of deep tunnels includes the following steps:

[0007] Step P1: Select and equip the drilling rig and drilling survey instrument, construct the borehole, and drill the borehole to the horizontal section of the deep stratum tunnel treatment area;

[0008] Step P2: After the borehole reaches the horizontal section of the tunnel treatment area, obtain basic lithological information of the strata, and carry out core sampling in sections according to the spatial location of the borehole. Then, conduct mechanical property tests on the obtained core samples to clarify the lithological characteristics of the strata.

[0009] Step P3: Run logging instruments down into the borehole to perform comprehensive logging and obtain the characteristics of fracture development around the borehole.

[0010] Step P4: After the comprehensive logging is completed, install the detection instrument integration module on the drill pipe and use the detection instrument integration module to detect the fracture distribution and hydrogeological conditions in the far field area.

[0011] Step P5 combines the stratigraphic lithological characteristics obtained in step P2, the borehole perimeter fracture development characteristics obtained in step P3, and the far-field fracture distribution and hydrogeological conditions obtained in step P4 to depict the complete geological characteristics of the tunnel excavation area.

[0012] The above-mentioned refined geological exploration method is applicable to surface pre-grouting construction of deep tunnels.

[0013] In step P1, the drilling is set to one or more holes;

[0014] When there is only one borehole, a single drilling rig is used for drilling. After drilling to the directional section, multiple branch holes are constructed and all branch holes are drilled to the horizontal section.

[0015] When there are multiple boreholes, a corresponding number of drilling rigs are used to drill synchronously, so that the multiple boreholes are drilled to the horizontal section.

[0016] The above-mentioned refined geological exploration method is applicable to surface pre-grouting construction of deep tunnels.

[0017] In step P1, a ZJ40 drilling rig with a drilling depth of up to 2000m is selected, and drilling is carried out using at least three levels of drilling tools. The drilling includes a straight section, a directional section, and a horizontal section.

[0018] The diameter of the tunnel is 5-20m, and the diameter of the straight section is greater than that of the inclined section, which is greater than that of the horizontal section.

[0019] During drilling, the straight section is drilled first. After the straight section is completed, the casing is run in and cementing is carried out. Then the directional drilling section is drilled. After the directional drilling section is completed, the casing is run in and cementing is carried out. Finally, the horizontal section is drilled, so that the horizontal sections are evenly distributed around the tunnel.

[0020] The above-mentioned refined geological exploration method is applicable to surface pre-grouting construction of deep tunnels.

[0021] In step P2, the specific process of coring includes the following steps:

[0022] Step P2-1: Connect a hydraulic core barrel to the drill string assembly. The hydraulic core barrel includes an inner tube for gripping the rock core and an outer tube sleeved outside the inner tube for driving the drill bit to cut the formation.

[0023] Step P2-2: Perform coring operations according to the preset coring points. After the drill bit moves to the corresponding coring point, stop drilling and fix the drill rod. Apply pump pressure to the ground to drive the inner tube of the coring cylinder to clamp the rock core. Then slowly lift the drill bit and take out the inner tube carrying the complete rock core to the ground.

[0024] In this process, a core sampling point is set up every 30–50m along the drilling direction. At the same time, the core sampling points are denser at locations of abrupt changes in lithology, based on the preliminary lithology identification results of logging while drilling and the cuttings logging data. Throughout the core sampling process, the drilling fluid circulation is kept stable to prevent the core from being eroded and damaged.

[0025] The above-mentioned refined stratum detection method applicable to surface pre-grouting construction of deep tunnels, in step P2, the specific process of conducting mechanical property tests on the obtained core samples is as follows: First, the core samples are uniformly numbered, photographed, and sealed. The sealing method is to use wax sealing or wrapping with plastic wrap; then, the drilling depth and spatial location information corresponding to each core sample are recorded; finally, mechanical tests, rock and mineral identification, and permeability tests are carried out in the laboratory to quantify the stratum lithology parameters and mechanical parameters. Among them, the mechanical tests include uniaxial compressive strength, elastic modulus, and Poisson's ratio tests.

[0026] The above-mentioned refined geological exploration method is applicable to surface pre-grouting construction of deep tunnels.

[0027] In step P3, the instruments used in the integrated logging include:

[0028] Ultrasonic imaging logging tools are used to acquire 360° high-resolution images of the borehole wall to visually identify fracture locations, apertures, occurrences, and rock layer interfaces.

[0029] High-precision natural gamma logging tools are used to measure the natural radioactivity of formations to distinguish clay content and assist in lithological classification.

[0030] Arrayed acoustic logging tools are used to measure the P-wave velocity and S-wave velocity of formations to calculate rock mechanical parameters and assess the degree of fracture development.

[0031] Dual lateral resistivity logging tools and microsphere focusing logging tools are used to detect changes in formation resistivity in order to identify fluid-bearing fractures or low-resistivity fracture zones.

[0032] Well temperature and caliper logging tools are used to monitor borehole temperature anomalies and caliper changes to indicate groundwater activity and reflect formation collapse or dissolution.

[0033] The above-mentioned refined geological exploration method is applicable to surface pre-grouting construction of deep tunnels.

[0034] In step P4, the detection instrument integration module includes an openable and closable geophysical exploration push device. A water pressure gauge, a transient electromagnetic instrument, and a ground-penetrating radar are fixedly installed inside the openable and closable geophysical exploration push device via an internal clamp. The transient electromagnetic instrument is equipped with a transmitting coil and a receiving coil. The ground-penetrating radar is equipped with a radio wave transmitting probe and a radio wave receiving probe.

[0035] The detection instrument integration module is assembled on the directional drill rod. The drill rod is pushed by the directional drilling machine to smoothly lower the detection instrument integration module to the preset detection depth of the horizontal section of the borehole. During the lowering process, the openable and closable geophysical exploration pushing device remains closed to protect the internal instruments.

[0036] Upon reaching the designated location, the ground control system sends a control signal to trigger the openable geophysical exploration pusher to release the instrument and initiate the detection process. The specific process is as follows: First, the internal clamp releases the fixed constraint on the instrument. Then, the signal modules at the cutting stop on the outer shell of the openable geophysical exploration pusher sequentially pop open. After all the signal modules have popped open, the built-in power circuit of each instrument automatically closes and powers on, and the instrument enters the working state and begins the detection operation.

[0037] The above-mentioned refined geological exploration method is applicable to surface pre-grouting construction of deep tunnels.

[0038] In step P4, hydrostatic pressure and water pressure fluctuations at different depths within the borehole are measured using a water pressure gauge to assess hydrological connectivity.

[0039] The transient electromagnetic instrument's transmitting coil emits a primary field pulse to the surrounding strata, and the receiving probe measures the induced secondary field. By analyzing the attenuation characteristics of the secondary field, a cylindrical spatial electrical structure map with a radial detection range of 10-100m centered on the borehole is constructed to reveal far-field fracture zones or water-bearing structures.

[0040] The ground-penetrating radar's radio wave transmitting probe emits high-frequency electromagnetic waves, while the radio wave receiving probe receives reflected waves from the strata surrounding the borehole, enabling precise detection of fractures and bedding structures within a 10–100m radius around the borehole.

[0041] Each instrument conducts point-by-point detection according to a preset procedure, and the detection data is transmitted and stored through a wired transmission system and a wireless storage module.

[0042] The above-mentioned refined stratigraphic exploration method applicable to surface pre-grouting construction of deep tunnels includes, in step P5, the characterization content including the construction of a three-dimensional lithological model, the characterization of key mechanical parameters, the zoning of hydrogeological features, and the location of far-field anomalies. Through the above-mentioned multi-dimensional refined three-dimensional characterization, a complete multi-dimensional geological information system is formed, providing direct, accurate and comprehensive geological basis for subsequent grouting process selection, grouting parameter optimization and grouting effect evaluation.

[0043] The above-mentioned refined geological exploration method applicable to surface pre-grouting construction of deep tunnels specifically includes the following characteristics:

[0044] By combining the mechanical property test results of core samples from each borehole segment, the lithological data obtained from drilling exploration and logging, a three-dimensional lithological distribution model of the tunnel perimeter is generated, and the key mechanical parameters of the corresponding area are obtained.

[0045] Based on ultrasonic imaging and sonic logging data from each borehole, characteristic parameters of fracture occurrence, density, and aperture were extracted. A three-dimensional development model of the main fracture groups around the tunnel was constructed through spatial interpolation analysis to clarify the direction of dominant fractures and potential connection paths.

[0046] By combining water-bearing signs identified by integrated well logging, actual pressure data measured by hydraulic gauges, and low-resistivity anomaly zones obtained by transient electromagnetic detection, the spatial range of groundwater-rich areas, potential seepage channels, and relative impermeable layers around the tunnel is delineated, and the spatial heterogeneity of hydrogeological conditions is assessed.

[0047] By integrating transient electromagnetic and ground-penetrating radar far-field detection data from various boreholes, the spatial location, development scale, and relative orientation of large-scale low-resistivity fracture zones, hidden karst caves, and water-rich structures within a certain range outside the tunnel outline are delineated, providing target areas for determining key areas for grouting reinforcement.

[0048] The technical solution of the present invention achieves the following beneficial technical effects:

[0049] This application not only focuses on borehole trajectory control, but also innovatively integrates multiple detection technologies such as hydraulic coring, integrated logging, water pressure monitoring, transient electromagnetic, and ground-penetrating radar within a given borehole. It actively and comprehensively acquires key geological information such as stratigraphic lithology, mechanical parameters, fracture development, hydrogeology, and far-field anomalies, effectively overcoming the shortcomings of traditional methods that rely solely on borehole trajectory to indirectly infer geological conditions, resulting in incomplete information and insufficient accuracy.

[0050] This application obtains lithological and mechanical parameters through segmented core sampling and mechanical property tests, achieves detailed analysis of near-field borehole wall geological features through integrated well logging, delineates deep and peripheral anomalies through far-field geophysical exploration, and then constructs a multi-dimensional three-dimensional geological model integrating lithological distribution, fracture development, hydrological zoning, and anomaly location through multi-source data fusion and spatial interpolation analysis. This enables a panoramic and quantitative characterization of the geological features of the tunnel treatment area in deep strata.

[0051] This application first implements comprehensive well logging to obtain accurate near-field geological data, providing constraints and calibration for far-field exploration and improving the accuracy of inversion interpretation. Simultaneously, conventional well logging is completed first to ensure unobstructed boreholes and wellbore stability, avoiding the risk of stuck drill bits during the deployment of complex instruments. While ensuring construction safety, this significantly improves the overall efficiency and reliability of exploration operations. Furthermore, the refined three-dimensional geological model and multi-dimensional geological information system of this application can provide direct, accurate, and comprehensive geological basis for subsequent grouting process selection, grouting parameter optimization, grouting material selection, and grouting effect evaluation. This achieves efficient integration of geological exploration and engineering treatment, effectively improving the targeting and effectiveness of tunnel surrounding rock reinforcement, water plugging and seepage prevention projects, and reducing engineering risks and costs. Attached Figure Description

[0052] Figure 1 Flowchart of the refined stratigraphic detection method of the present invention;

[0053] Figure 2 A schematic diagram of borehole construction in the refined formation detection method of this invention;

[0054] Figure 3 A cross-sectional view of the borehole layout in the refined formation detection method of this invention.

[0055] The reference numerals in the figure are as follows: 1-Drilling rig; 2-Surface; 3-Vertical borehole section; 4-Angled section; 5-Horizontal section; 6-Tunnel; 7-Integrated module of detection instrument; 8-Outline of borehole layout; 9-Outline of tunnel excavation. Detailed Implementation

[0056] This embodiment discloses a refined geological exploration method applicable to surface pre-grouting construction of deep tunnels, such as... Figure 1 As shown,

[0057] Includes the following steps:

[0058] Step P1: Select drilling rig 1 and drilling survey instrument, construct the borehole, and drill the borehole to the horizontal section 5 of the treatment area of ​​the deep stratum tunnel 6;

[0059] Specifically, the borehole is configured as one or more; when there is only one borehole, a single drilling rig 1 is used and set up on the ground surface 2 for drilling. After drilling to the inclined section 4, multiple branch holes are constructed, and all branch holes are drilled to the horizontal section 5; for example Figure 2 and Figure 3 As shown, when there are multiple boreholes, a corresponding number of drilling rigs 1 are used to drill simultaneously, so that the multiple boreholes are drilled to the horizontal section 5. The distribution of the boreholes is as follows. Figure 3 The borehole layout outline is shown in 8, and the boreholes are distributed around the tunnel excavation outline 9.

[0060] The drilling rig 1, equipped with a ZJ40 type, can reach a drilling depth of up to 2000m. Drilling is carried out using at least three stages of drilling tools. The borehole includes a vertical section 3, a directional drilling section 4, and a horizontal section 5. The diameter of the tunnel 6 is 5-20m. The diameter of the vertical section 3 is larger than that of the directional drilling section 4, which is larger than that of the horizontal section 5. During drilling, the vertical section 3 is drilled first. After the vertical section 3 is completed, casing is installed and cementing is performed. Then, the directional drilling section 4 is drilled. After the directional drilling section 4 is completed, casing is installed and cementing is performed. Finally, the horizontal section 5 is drilled, ensuring that the horizontal sections 5 are evenly distributed around the tunnel 6.

[0061] Step P2: After the borehole reaches the horizontal section 5 of the treatment area of ​​Tunnel 6, basic lithological information of the strata is obtained. Based on the spatial location of the borehole, core sampling is carried out in sections. Then, mechanical property tests are conducted on the obtained core samples to clarify the lithological characteristics of the strata. The specific process of core sampling includes the following steps:

[0062] Step P2-1: Connect a hydraulic core sampler (or a mechanical core sampler, which controls core sampling through mechanical components) to the drill string assembly. The hydraulic core sampler includes an inner tube for gripping the rock core and an outer tube sleeved outside the inner tube for driving the drill bit to cut the formation.

[0063] Step P2-2: Perform coring operations according to the preset coring points. After the drill bit moves to the corresponding coring point, stop drilling and fix the drill rod. Apply pump pressure to the ground to drive the inner tube of the coring cylinder to clamp the rock core. Then slowly lift the drill bit and take out the inner tube carrying the complete rock core to the ground.

[0064] In this process, a core sampling point is set up every 30–50m along the drilling direction. At the same time, the core sampling points are densely set up at the locations of lithological abrupt changes, based on the preliminary lithological identification results of logging while drilling and the cuttings logging data (the location of lithological abrupt changes can be obtained through logging while drilling, which includes natural gamma and resistivity). Throughout the core sampling process, the drilling fluid circulation is kept stable to prevent the core from being eroded and damaged.

[0065] The specific process for conducting mechanical property tests on the obtained core samples is as follows: First, the core samples are uniformly numbered, photographed, and sealed. The sealing method is to use wax sealing or wrapping with plastic wrap. Then, the drilling depth and spatial location information corresponding to each core sample are recorded. Finally, mechanical tests, rock and mineral identification, and permeability tests are carried out in the laboratory to quantify the lithological parameters and mechanical parameters of the formation. Among them, the mechanical tests include uniaxial compressive strength, elastic modulus, and Poisson's ratio tests.

[0066] Step P3: Perform comprehensive logging by lowering logging instruments into the borehole to obtain information on the fracture development characteristics around the borehole. The instruments used for comprehensive logging include:

[0067] Ultrasonic imaging logging tools are used to acquire 360° high-resolution images of the borehole wall to visually identify fracture locations, apertures, occurrences, and rock layer interfaces.

[0068] High-precision natural gamma logging tools are used to measure the natural radioactivity of formations to distinguish clay content and assist in lithological classification.

[0069] Arrayed acoustic logging tools are used to measure the P-wave velocity and S-wave velocity of formations to calculate rock mechanical parameters (such as Poisson's ratio and Young's modulus) and assess the degree of fracture development.

[0070] Dual lateral resistivity logging tools and microsphere focusing logging tools are used to detect changes in formation resistivity in order to identify fluid-bearing fractures or low-resistivity fracture zones.

[0071] Well temperature and caliper logging tools are used to monitor borehole temperature anomalies and caliper changes to indicate groundwater activity and reflect formation collapse or dissolution.

[0072] Step P4: After the comprehensive logging is completed, install the detection instrument integration module 7 on the drill pipe and use the detection instrument integration module 7 to detect the fracture distribution and hydrogeological conditions in the far field area.

[0073] Integrated logging is prioritized because it provides precise information on lithology, fracture development, and wellbore integrity within the borehole wall and near-field (typically within 0.5m). Far-field exploration is conducted after integrated logging is completed for the following reasons:

[0074] ① Data foundation and calibration: Near-field geological results obtained from integrated well logging can provide key geological constraints and calibration basis for the interpretation of far-field exploration data, effectively improving the accuracy of far-field data inversion and interpretation.

[0075] ② Operational safety and efficiency: Prioritize routine integrated logging without additional complex equipment to ensure smooth borehole flow and wellbore stability, avoid the risk of stuck drill bit caused by premature installation of the integrated detection instrument module 7, ensure the safety of exploration operations, and improve construction efficiency.

[0076] ③ Detection logic sequence: Following the exploration principle of "from near to far", after clarifying the geological characteristics of the borehole in the near field, targeted far field detection is carried out. This can optimize detection parameters such as transmission frequency and transmission power, and focus on suspicious anomaly areas indicated by near field data, thereby improving the targeting and effectiveness of the detection.

[0077] The detection instrument integration module 7 includes an openable and closable geophysical exploration push device, in which a water pressure gauge, a transient electromagnetic instrument, and a ground-penetrating radar are fixedly installed by an internal clamp; wherein, the transient electromagnetic instrument is equipped with a transmitting coil and a receiving coil; and the ground-penetrating radar is equipped with an electromagnetic wave transmitting probe and an electromagnetic wave receiving probe.

[0078] The detection instrument integration module 7 is assembled on the directional drill rod. The drill rod is pushed by the directional drilling machine to smoothly lower the detection instrument integration module 7 to the preset detection depth of the horizontal section 5 of the borehole. During the lowering process, the openable and closable geophysical exploration pushing device remains closed to protect the internal instruments.

[0079] Upon reaching the designated location, the ground control system sends a control signal to trigger the openable geophysical exploration pusher to release the instrument and initiate the detection process. The specific process is as follows: First, the internal clamp releases the fixed constraint on the instrument. Then, the signal modules at the cutting stop on the outer shell of the openable geophysical exploration pusher sequentially pop open. After all the signal modules have popped open, the built-in power circuit of each instrument automatically closes and powers on, and the instrument enters the working state and begins the detection operation.

[0080] Hydrological connectivity is assessed by measuring hydrostatic pressure and water pressure fluctuations at different depths within the borehole using a water pressure gauge.

[0081] The transient electromagnetic instrument's transmitting coil emits a primary field pulse to the surrounding strata, and the receiving probe measures the induced secondary field. By analyzing the attenuation characteristics of the secondary field, a cylindrical spatial electrical structure map with a radial detection range of 10-100m centered on the borehole is constructed to reveal far-field fracture zones or water-bearing structures.

[0082] The ground-penetrating radar's radio wave transmitting probe emits high-frequency electromagnetic waves, while the radio wave receiving probe receives reflected waves from the strata surrounding the borehole, enabling precise detection of fractures and bedding structures within a 10–100m radius around the borehole.

[0083] Each instrument conducts point-by-point detection according to a preset procedure, and the detection data is transmitted and stored through a wired transmission system and a wireless storage module.

[0084] Step P5, combining the stratigraphic lithology characteristics obtained in step P2, the borehole perimeter fracture development characteristics obtained in step P3, and the far-field fracture distribution and hydrogeological conditions obtained in step P4, depicts the complete geological characteristics of the tunnel 6 excavation area.

[0085] The characterization includes the construction of a three-dimensional lithological model, field characterization of key mechanical parameters, spatial distribution of fracture networks, zoning of hydrogeological features, and location of far-field anomalies. Through this multi-dimensional and refined three-dimensional characterization, a complete multi-dimensional geological information system is formed, providing direct, accurate, and comprehensive geological basis for subsequent grouting process selection, grouting parameter optimization, and grouting effect evaluation. Specifically,

[0086] Three-dimensional lithological model construction and key mechanical parameter field characterization: Based on the mechanical performance test results of core samples from each borehole segment, lithological data obtained from drilling exploration and logging, a three-dimensional lithological distribution model of the area surrounding Tunnel 6 was generated, and the key mechanical parameters of the corresponding area were obtained.

[0087] Spatial distribution of fracture network: Based on data from ultrasonic imaging and sonic logging of each borehole, characteristic parameters such as fracture occurrence, density and aperture are extracted. A three-dimensional development model of the main fracture groups around Tunnel 6 is constructed through spatial interpolation analysis to clarify the direction of dominant fractures and potential connection paths.

[0088] Hydrogeological feature zoning: Combining the water-bearing signs identified by comprehensive well logging, the actual pressure data measured by the barometer, and the low-resistivity anomaly area obtained by transient electromagnetic detection, the spatial range of the groundwater-rich area, potential seepage channels, and relative impermeable layers around Tunnel 6 is delineated to assess the spatial heterogeneity of hydrogeological conditions.

[0089] Far-field anomaly location: Integrate far-field detection data from transient electromagnetic and ground-penetrating radar of each borehole to delineate the spatial location, development scale, and relative orientation of large-scale low-resistivity fractured zones, hidden karst caves, and water-rich structures within a certain range outside the outline of tunnel 6 (the certain range is at least 10m), providing target areas for determining key areas for grouting reinforcement.

[0090] It should be noted that the drilling rig 1, drilling comprehension instrument, integrated logging instruments, coring instruments, hydraulic gauge, transient electromagnetic instrument, ground-penetrating radar and radio wave transmitting and receiving device mentioned in this application are all conventional devices in this field, and through research, it has been found that they all meet the 1500m detection requirement. Specific models will not be described in detail.

[0091] The above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of the claims of this patent application.

Claims

1. A refined geological exploration method applicable to surface pre-grouting construction of deep tunnels, characterized in that, Includes the following steps: Step P1: Select and equip the drilling rig (1) and the drilling survey instrument, construct the borehole, and drill the borehole to the horizontal section (5) of the treatment area of ​​the deep stratum tunnel (6). Step P2: After the borehole reaches the horizontal section (5) of the treatment area of ​​the tunnel (6), obtain basic lithological information of the strata, and carry out core sampling in sections according to the spatial location of the borehole. Then, conduct mechanical property tests on the obtained core samples to clarify the lithological characteristics of the strata. Step P3: Run logging instruments down into the borehole to perform comprehensive logging and obtain the characteristics of fracture development around the borehole. Step P4: After the comprehensive logging is completed, install the detection instrument integration module (7) on the drill pipe and use the detection instrument integration module (7) to detect the fracture distribution and hydrogeological conditions in the far field area. Step P5, combining the stratigraphic lithology characteristics obtained in step P2, the borehole perimeter fracture development characteristics obtained in step P3, and the far-field fracture distribution and hydrogeological conditions obtained in step P4, depicts the complete geological characteristics of the tunnel (6) excavation area.

2. The refined geological exploration method for surface pre-grouting construction of deep tunnels according to claim 1, characterized in that, In step P1, the drilling is set to one or more holes; When there is only one borehole, a single drilling rig (1) is used for drilling. After drilling to the directional section (4), multiple branch holes are constructed and all branch holes are drilled to the horizontal section (5). When there are multiple boreholes, a corresponding number of drilling rigs (1) are used to drill synchronously, so that the multiple boreholes are drilled to the horizontal section (5).

3. The refined geological exploration method for surface pre-grouting construction of deep tunnels according to claim 2, characterized in that, In step P1, a ZJ40 drilling rig (1) with a drilling depth of up to 2000m is selected, and drilling is carried out using at least three levels of drilling tools. The drilling includes a straight section (3), a directional section (4), and a horizontal section (5). The diameter of the tunnel (6) is 5-20m, and the diameter of the straight section (3) is greater than the diameter of the inclined section (4) and greater than the diameter of the horizontal section (5). During drilling, the straight hole section (3) is drilled first. After the straight hole section (3) is completed, the casing is installed and cementing is carried out. Then the directional drilling section (4) is drilled. After the directional drilling section (4) is completed, the casing is installed and cementing is carried out. Finally, the horizontal section (5) is drilled so that the horizontal section (5) is evenly distributed around the tunnel (6).

4. The refined geological exploration method for surface pre-grouting construction of deep tunnels according to claim 1, characterized in that, In step P2, the specific process of coring includes the following steps: Step P2-1: Connect a hydraulic core barrel to the drill assembly. The hydraulic core barrel includes an inner tube for gripping the rock core and an outer tube sleeved outside the inner tube for driving the drill bit to cut the formation. Step P2-2: Perform coring operations according to the preset coring points. After the drill bit moves to the corresponding coring point, stop drilling and fix the drill rod. Apply pump pressure to the ground to drive the inner tube of the coring cylinder to clamp the rock core. Then slowly lift the drill bit and take out the inner tube carrying the complete rock core to the ground. In this process, a core sampling point is set up every 30–50m along the drilling direction. At the same time, the core sampling points are denser at locations of abrupt changes in lithology, based on the preliminary lithology identification results of logging while drilling and the cuttings logging data. Throughout the core sampling process, the drilling fluid circulation is kept stable to prevent the core from being eroded and damaged.

5. The refined geological exploration method for surface pre-grouting construction of deep tunnels according to any one of claims 1-4, characterized in that, In step P2, the specific process of conducting mechanical property tests on the obtained core samples is as follows: First, the core samples are uniformly numbered, photographed, and sealed. The sealing method is to use wax sealing or wrapping with plastic wrap. Then, the drilling depth and spatial location information corresponding to each core sample are recorded. Finally, mechanical tests, rock and mineral identification, and permeability tests are carried out in the laboratory to quantify the lithological parameters and mechanical parameters of the formation. The mechanical tests include uniaxial compressive strength, elastic modulus, and Poisson's ratio tests.

6. The refined geological exploration method for surface pre-grouting construction of deep tunnels according to claim 1, characterized in that, In step P3, the instruments used in the integrated logging include: Ultrasonic imaging logging tools are used to acquire 360° high-resolution images of the borehole wall to visually identify fracture locations, apertures, occurrences, and rock layer interfaces. High-precision natural gamma logging tools are used to measure the natural radioactivity of formations to distinguish clay content and assist in lithological classification. Arrayed acoustic logging tools are used to measure the P-wave velocity and S-wave velocity of formations to calculate rock mechanical parameters and assess the degree of fracture development. Dual lateral resistivity logging tools and microsphere focusing logging tools are used to detect changes in formation resistivity in order to identify fluid-bearing fractures or low-resistivity fracture zones. Well temperature and caliper logging tools are used to monitor borehole temperature anomalies and caliper changes to indicate groundwater activity and reflect formation collapse or dissolution.

7. The refined geological exploration method for surface pre-grouting construction of deep tunnels according to claim 1, characterized in that, In step P4, the detection instrument integration module (7) includes an openable and closable geophysical exploration push device. A water pressure gauge, a transient electromagnetic instrument, and a ground-penetrating radar are fixedly installed inside the openable and closable geophysical exploration push device through a pipe clamp. The transient electromagnetic instrument is equipped with a transmitting coil and a receiving coil. The ground-penetrating radar is equipped with a radio wave transmitting probe and a radio wave receiving probe. The detection instrument integration module (7) is assembled on the directional drill rod. The drill rod is pushed by the directional drilling machine to smoothly lower the detection instrument integration module (7) to the preset detection depth of the horizontal section of the borehole. During the lowering process, the openable and closable geophysical exploration pushing device remains closed to protect the internal instruments. Upon reaching the designated location, the ground control system sends a control signal to trigger the openable geophysical exploration pusher to release the instrument and initiate the detection process. The specific process is as follows: First, the internal clamp releases the fixed constraint on the instrument. Then, the signal modules at the cutting stop on the outer shell of the openable geophysical exploration pusher sequentially pop open. After all the signal modules have popped open, the built-in power circuit of each instrument automatically closes and powers on, and the instrument enters the working state and begins the detection operation.

8. The refined geological exploration method for surface pre-grouting construction of deep tunnels according to claim 7, characterized in that, In step P4, hydrostatic pressure and water pressure fluctuations at different depths within the borehole are measured using a water pressure gauge to assess hydrological connectivity. The transient electromagnetic instrument's transmitting coil emits a primary field pulse to the surrounding strata, and the receiving probe measures the induced secondary field. By analyzing the attenuation characteristics of the secondary field, a cylindrical spatial electrical structure map with a radial detection range of 10-100m centered on the borehole is constructed to reveal far-field fracture zones or water-bearing structures. The ground-penetrating radar's radio wave transmitting probe emits high-frequency electromagnetic waves, while the radio wave receiving probe receives reflected waves from the strata surrounding the borehole, enabling precise detection of fractures and bedding structures within a 10–100m radius around the borehole. Each instrument conducts point-by-point detection according to a preset procedure, and the detection data is transmitted and stored through a wired transmission system and a wireless storage module.

9. The refined geological exploration method for surface pre-grouting construction of deep tunnels according to claim 1, characterized in that, In step P5, the characterization includes the construction of a three-dimensional lithological model, the characterization of key mechanical parameters, the zoning of hydrogeological features, and the location of far-field anomalies. Through the above multi-dimensional and refined three-dimensional characterization, a complete multi-dimensional geological information system is formed, providing direct, accurate, and comprehensive geological basis for subsequent grouting process selection, grouting parameter optimization, and grouting effect evaluation.

10. The refined geological exploration method for surface pre-grouting construction of deep tunnels according to claim 9, characterized in that, The specific content depicted includes: Based on the mechanical property test results of core samples taken from each borehole segment, the lithological data obtained from drilling exploration and logging, a three-dimensional lithological distribution model of the area surrounding the tunnel (6) is generated, and the key mechanical parameters of the corresponding area are obtained. Based on ultrasonic imaging and sonic logging data from each borehole, characteristic parameters of fracture occurrence, density, and aperture were extracted. A three-dimensional development model of the main fracture groups around the tunnel (6) was constructed through spatial interpolation analysis to clarify the direction of dominant fractures and potential connection paths. Combining the water-bearing signs identified by comprehensive well logging, the actual pressure data measured by the water pressure gauge, and the low-resistivity anomaly area obtained by transient electromagnetic detection, the spatial range of the groundwater-rich area, potential seepage channels, and relative impermeable layer around the tunnel (6) is delineated to assess the spatial heterogeneity of hydrogeological conditions. By integrating the far-field detection data of transient electromagnetic and ground-penetrating radar from each borehole, the spatial location, development scale, and relative orientation of large-scale low-resistivity fracture zones, hidden karst caves, and water-rich structures within a certain range outside the tunnel (6) outline are delineated, providing a target area for determining the key areas for grouting reinforcement.

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