A method for horizontal directional drilling layout in tunnels

Abstract

This invention relates to the field of tunnel drilling technology, specifically to a method for arranging horizontal directional boreholes in tunnels, comprising the following steps: selecting the tunnel excavation process. When using the drill-and-blast method, the borehole locations for horizontal directional drilling are arranged within the outline of the tunnel face. When using a tunnel boring machine (TBM) or shield tunneling method, the borehole locations for horizontal directional drilling are arranged outside the outline of the tunnel face; simultaneously, based on the rock strata's attitude, the rock strata to be excavated are divided into five categories, and the borehole locations are arranged according to these categories. By selecting the arrangement locations of the horizontal directional boreholes based on different tunnel excavation processes and the attitude of the rock strata to be excavated, this method reduces reliance on experience-based judgment, making the borehole arrangement more scientific and rational, avoiding unnecessary drilling operations, thereby reducing the number of boreholes and the workload of exploration, and ultimately reducing exploration costs and shortening the exploration cycle.

Description

Technical Field

[0001] This invention relates to the field of tunnel drilling technology, and in particular to a method for arranging horizontal directional boreholes in a tunnel. Background Technology

[0002] With the rapid development of my country's transportation network infrastructure, large-scale engineering projects such as railways and highways are springing up like mushrooms in western regions, especially mountainous areas. These projects often face complex and varied terrain challenges, characterized by significant elevation differences and dramatic undulations. Therefore, the adoption of long, deep-buried tunnels as a key engineering technology solution for traversing mountainous areas has become inevitable. In the preliminary exploration stage of long, deep-buried tunnels, horizontal directional drilling technology plays a crucial role. However, current drilling operations face a series of severe challenges, including but not limited to high implementation difficulty, high economic costs, and long operation cycles. These factors collectively constitute a major obstacle to achieving high-precision exploration of long, deep-buried tunnels.

[0003] In current practice, the layout of boreholes mainly relies on the engineering intuition and experience of on-site technicians. This approach is highly subjective and often lacks sufficient specificity and theoretical support. In order to ensure the accuracy of the exploration results, there is a tendency to increase the number and depth of drilling. While this approach can improve the accuracy of the exploration, it also increases the exploration cost and prolongs the exploration cycle. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies, such as the reliance on experience-based judgment for borehole layout in horizontal directional drilling, which lacks specificity and leads to increased exploration costs and extended exploration cycles. This invention provides a method for laying out horizontal directional boreholes in tunnels.

[0005] This invention provides a method for arranging horizontal directional boreholes in a tunnel, comprising the following steps:

[0006] S1: Select tunnel excavation technology;

[0007] S2: When using the drill-and-blast method for excavation, the boreholes for horizontal directional drilling are located within the outline of the tunnel face.

[0008] When using tunnel boring machines or shield tunneling methods for excavation, the boreholes for horizontal directional drilling are located outside the outline of the tunnel face. Based on the rock strata attitude, the rock strata to be excavated are divided into five categories: rock strata with the same dip direction as the tunnel axis, rock strata with the bedding plane parallel to the horizontal plane, rock strata with the bedding plane perpendicular to the horizontal plane, rock strata with the bedding plane tilting to the left, and rock strata with the bedding plane tilting to the right.

[0009] When the rock stratum to be excavated is a rock stratum whose dip direction is consistent with the tunnel axis, a borehole shall be arranged outside the outline of the tunnel face, and the azimuth angle of the borehole position shall be 90° or 270°.

[0010] When the rock stratum to be excavated is a rock stratum whose bedding plane is parallel to the horizontal plane, two boreholes are arranged outside the outline of the tunnel face, with the azimuth angles of the two boreholes being 0° and 180° respectively.

[0011] When the rock stratum to be excavated is a rock stratum whose bedding plane is perpendicular to the horizontal plane, a borehole is arranged outside the outline of the tunnel face, and the azimuth angle of the borehole position is 90° or 270°.

[0012] When the rock stratum to be excavated is a rock stratum with the stratum surface tilting to the left, two boreholes are arranged outside the outline of the tunnel face. The two boreholes are located in the first area and the second area outside the outline of the tunnel face, respectively.

[0013] When the rock stratum to be excavated is a rock stratum with the stratum surface tilting to the right, two boreholes are arranged outside the outline of the tunnel face. The two boreholes are located in the third and fourth regions outside the outline of the tunnel face, respectively.

[0014] This invention provides a method for arranging horizontally directional boreholes in tunnels. The method selects the locations of the boreholes for horizontal directional drilling based on different tunnel excavation techniques and the orientation of the rock strata to be excavated. This method reduces reliance on experience-based judgment, making the borehole arrangement more scientific and rational, avoiding unnecessary drilling operations, thereby reducing the number of boreholes and the workload of exploration, ultimately lowering exploration costs and shortening the exploration cycle.

[0015] The selection of tunnel excavation technology is based on existing technology. Generally, the appropriate excavation technology is selected according to geological conditions, tunnel length, and cross-sectional size. Excavation technologies that can be used include drill and blast method, tunnel boring machine or shield tunneling method, etc.

[0016] When using the drill-and-blast method for excavation, the boreholes for horizontal directional drilling are located within the outline of the tunnel face. The number of boreholes can be one or more.

[0017] The tunnel face refers to the excavation face that is perpendicular to the longitudinal axis of the tunnel excavation.

[0018] The line of intersection between a rock stratum and any imaginary horizontal plane is called a strike line, which is the line connecting two points of equal height on the same stratum. The directions extending from both ends of the strike line are called the strike of the rock stratum, which indicates the horizontal extension direction of the rock stratum in space. A straight line drawn perpendicular to the strike line and downwards along the slope on the rock stratum is called a dip line, which indicates the maximum slope of the rock stratum. The direction indicated by the projection of the dip line onto the horizontal plane is called the dip direction of the rock stratum, and the acute angle between the dip line and the horizontal plane is called the true dip angle of the rock stratum.

[0019] When the direction of tunnel excavation is consistent with the direction of rock strata dip, such rock strata are said to be rock strata whose dip direction is consistent with the direction of tunnel axis.

[0020] A rock stratum whose bedding plane is parallel to the horizontal plane specifically refers to a rock stratum where all points on the same bedding plane have the same elevation; it is also called a horizontal rock stratum.

[0021] A rock stratum whose bedding plane is perpendicular to the horizontal plane, specifically, a rock stratum whose bedding plane forms a 90° angle with the horizontal plane, is also called an upright rock stratum.

[0022] When an observer stands at the tunnel face facing the rock stratum to be excavated, if the rock stratum to be excavated can be made horizontal by rotating its surface clockwise around its strike line by an angle (the angle being the true dip angle of the rock stratum to be excavated), then such a rock stratum is called a rock stratum whose surface dips to the left.

[0023] When an observer stands at the tunnel face facing the rock stratum to be excavated, if the rock stratum to be excavated can be made horizontal by rotating its surface counterclockwise around its strike line by an angle (the angle being the true dip angle of the rock stratum to be excavated), then such a rock stratum is called a rock stratum whose surface dips to the right.

[0024] The azimuth angle refers to the angle defined by rotating clockwise from the center of the tunnel face to the 12 o'clock position (directly above).

[0025] The first region refers to the area above and to the left of the tunnel when an observer stands at the tunnel face facing the excavated rock strata.

[0026] The second region refers to the area to the lower right of the tunnel when an observer stands at the tunnel face facing the excavated rock strata.

[0027] The third region refers to the area above and to the right of the tunnel when an observer stands at the tunnel face facing the excavated rock strata.

[0028] The fourth region refers to the area to the lower left of the tunnel when an observer stands at the tunnel face facing the excavated rock strata.

[0029] Preferably, in step S2, when using the drill-and-blast method for excavation, the boreholes for horizontal directional drilling are located within a circular area with a radius of 2 meters at the center of the tunnel face. This scheme further enhances the targeting and precision of the borehole layout for horizontal directional drilling when using the drill-and-blast method for excavation.

[0030] Preferably, in step S2, when using the drill-and-blast method for excavation, the boreholes for horizontal directional drilling are positioned at the center of the tunnel face. This approach allows for a more direct determination of the borehole layout, further improving exploration and construction efficiency. By precisely positioning the boreholes at the center of the tunnel face, this approach enables a more effective assessment of the geological conditions ahead of the face, providing accurate geological information for subsequent blasting operations and reducing construction delays and adjustments caused by geological uncertainties.

[0031] Preferably, in step S2, when the rock stratum to be excavated is a rock stratum with its bedding inclined to the left, the azimuth angles of the two borehole locations are β1 and β2, respectively, and the formulas for calculating β1 and β2 are as follows:

[0032] β1 = 270° + α

[0033] β2=90°+α

[0034] α = arctan(ηtanγsinμ)

[0035] Wherein, β1 represents the azimuth angle when the borehole is located in the upper left of the tunnel; β2 represents the azimuth angle when the borehole is located in the lower right of the tunnel; α represents the apparent dip angle of the rock strata; η represents the ratio of the longitudinal scale to the transverse scale, wherein the longitudinal scale represents the ratio of the length in the vertical direction (i.e., the depth direction of the rock strata) on the cross-section to the vertical length of the actual geological body, and the transverse scale represents the ratio of the length in the horizontal direction on the cross-section to the horizontal length of the actual geological body; γ is the true dip angle of the rock strata; and μ is the angle between the strike of the rock strata and the tunnel face.

[0036] The plan further clarifies the arrangement of boreholes for horizontal directional drilling when the rock strata to be excavated are those that slope to the left.

[0037] The apparent dip angle of a rock stratum is defined as follows: when a cross-section intersects the strike of a rock stratum at an oblique angle, the line of intersection between the rock stratum and the cross-section is called the apparent dip line, and the angle between the apparent dip line and its projection line on the horizontal plane is called the apparent dip angle of the rock stratum. In this application, the cross-section corresponds to the tunnel face.

[0038] Preferably, in step S2, when the rock stratum to be excavated is a rock stratum with its bedding inclined to the right, the azimuth angles of the two borehole locations are β3 and β4, respectively, and the formulas for calculating β3 and β4 are as follows:

[0039] β3=90°-α

[0040] β4=270°-α

[0041] α = arctan(ηtanγsinμ)

[0042] Wherein, β3 represents the azimuth angle when the borehole is located to the upper right of the tunnel; β4 represents the azimuth angle when the borehole is located to the lower left of the tunnel; α represents the apparent dip angle of the rock strata; η represents the ratio of the longitudinal scale to the transverse scale, wherein the longitudinal scale represents the ratio of the length in the vertical direction (i.e., the depth direction of the rock strata) on the cross-section to the vertical length of the actual geological body, and the transverse scale represents the ratio of the length in the horizontal direction on the cross-section to the horizontal length of the actual geological body; γ is the true dip angle of the rock strata; and μ is the angle between the strike of the rock strata and the tunnel face.

[0043] The plan further clarifies the arrangement of boreholes for horizontal directional drilling when the rock strata to be excavated are rock strata that slope to the right.

[0044] Preferably, in step S2, when a tunnel boring machine or shield tunneling method is used for excavation, the boreholes for horizontal directional drilling are located 1 to 5 meters outside the outline of the tunnel face.

[0045] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0046] 1. This invention provides a method for arranging horizontal directional boreholes in tunnels. The method selects the locations of the boreholes for horizontal directional drilling based on different tunnel excavation techniques and the orientation of the rock strata to be excavated. This method reduces reliance on experience-based judgment, making the borehole arrangement more scientific and rational, avoiding unnecessary drilling operations, thereby reducing the number of boreholes and the workload of exploration, ultimately lowering exploration costs and shortening the exploration cycle. Attached Figure Description

[0047] Figure 1 This is a flowchart of a method for arranging horizontal directional boreholes in a tunnel.

[0048] Figure 2 This is a schematic diagram of the first cross-section.

[0049] Figure 3 This is a schematic diagram of the second cross-section.

[0050] Figure 4 This is a schematic diagram of the first longitudinal section.

[0051] Figure 5 This is a schematic diagram of the third cross section.

[0052] Figure 6 This is a schematic diagram of the second longitudinal section.

[0053] Figure 7This is a schematic diagram of the fourth cross section.

[0054] Figure 8 This is a schematic diagram of the fifth cross section.

[0055] Figure 9 This is a schematic diagram of the sixth cross section.

[0056] Figure 10 This is a cross-sectional schematic diagram of Case 1 in Example 2.

[0057] Figure 11 This is a cross-sectional schematic diagram of Case 2 in Example 2.

[0058] Marked in the image:

[0059] 1-The rock stratum to be excavated, 2-Outline, 3-Drilling location, 4-Rock stratum interface, 5-First zone, 6-Second zone, 7-Third zone, 8-Fourth zone. Detailed Implementation

[0060] The present invention will now be described in further detail with reference to specific embodiments. However, this should not be construed as limiting the scope of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0061] Unless otherwise specified, the use of terms such as "upper," "lower," "left," "right," "center," "inner," and "outer" to indicate orientation or positional relationships in the description of specific embodiments of the present invention is based on the orientation or positional relationships shown in the accompanying drawings, or the orientation or positional relationship in which the product / equipment / device is typically placed during use. These terms are merely for the purpose of facilitating the description of the present invention or simplifying the description in specific embodiments, enabling those skilled in the art to quickly understand the solution, and do not indicate or imply that a particular device / component / element must have a specific orientation, or be constructed and operated in a specific positional relationship. Therefore, they should not be construed as limitations on the present invention.

[0062] Furthermore, the use of terms such as "horizontal," "vertical," "suspended," and "parallel" does not imply that the corresponding device / component / element must be absolutely horizontal, vertical, suspended, or parallel, but rather that it can be slightly tilted or have a deviation. For example, "horizontal" merely means that its direction is more horizontal relative to "vertical," not that the structure must be completely horizontal, but that it can be slightly tilted. Alternatively, it can be simplified to mean that the corresponding device / component / element, when set in a "horizontal," "vertical," "suspended," or "parallel" direction, can have an error / deviation of ±10% relative to the corresponding direction, more preferably within ±8%, more preferably within ±6%, more preferably within ±5%, and more preferably within ±4%. As long as the corresponding device / component / element is within the error / deviation range, it can still achieve its function in the present invention.

[0063] Furthermore, the use of terms such as "first," "second," and "third" in terminology is merely for distinguishing descriptions of identical or similar components and should not be interpreted as emphasizing or implying the relative importance of a particular component.

[0064] Furthermore, in the description of the embodiments of the present invention, "several", "more than", and "a number of" represent at least two. The number can be any number, such as 2, 3, 4, 5, 6, 7, 8, or 9, and can even exceed nine.

[0065] Furthermore, in the description of the technical solution of this invention, unless otherwise explicitly specified / limited / restricted, the terms "set up," "install," "connect," "link," "provided with," "laid out," and "arranged" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to common connection methods in the art, such as welding, riveting, bolting, and threaded connections. Such connections can be mechanical, electrical, or communication connections; they can be direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components.

[0066] Example 1

[0067] like Figure 1 As shown, a method for arranging horizontal directional boreholes in a tunnel includes the following steps:

[0068] S1: Select the tunnel excavation method. Specific excavation methods available include: drill and blast method, tunnel boring machine method, and shield tunneling method.

[0069] S2: When using the drill-and-blast method for excavation, the borehole positions 3 of the horizontal directional drilling are arranged within the outline 2 of the tunnel face.

[0070] When using a tunnel boring machine or shield tunneling method for excavation, the borehole positions 3 of the horizontal directional drilling are arranged outside the outline 2 of the tunnel face. Based on the rock strata attitude, the rock strata to be excavated 1 are divided into five categories: rock strata with the rock strata dipped in the same direction as the tunnel axis, rock strata with the rock strata bedding parallel to the horizontal plane, rock strata with the rock strata bedding perpendicular to the horizontal plane, rock strata with the rock strata bedding to the left, and rock strata with the rock strata bedding to the right.

[0071] When the rock stratum 1 to be excavated is a rock stratum whose dip direction is consistent with the tunnel axis, such as Figure 3 , Figure 4 As shown, a borehole is arranged outside the outline 2 of the tunnel face, with the borehole location 3 having an azimuth angle of 90° or 270°. The boundary 4 between two adjacent rock layers is the rock layer interface. Figure 4 The area between the two dotted lines is the rock stratum 1 to be excavated.

[0072] When the rock stratum 1 to be excavated is a rock stratum whose bedding plane is parallel to the horizontal plane, such as Figure 5 , Figure 6 As shown, two boreholes are arranged outside the outline 2 of the tunnel face, with the azimuth angles of the two borehole positions 3 being 0° and 180° respectively. Figure 6 The area between the two dotted lines is the rock stratum 1 to be excavated.

[0073] When the rock stratum 1 to be excavated is a rock stratum whose bedding plane is perpendicular to the horizontal plane, such as Figure 7 As shown, a borehole is arranged outside the outline 2 of the tunnel face, and the azimuth angle of the borehole position 3 is 90° or 270°.

[0074] When the rock stratum 1 to be excavated is a rock stratum with its bedding inclined to the left, if Figure 8 As shown, two boreholes are arranged outside the outline 2 of the tunnel face. The two borehole positions 3 are located in the first region 5 and the second region 6 outside the outline 2 of the tunnel face, respectively.

[0075] When the rock stratum 1 to be excavated is a rock stratum with its bedding inclined to the right, if Figure 9 As shown, two boreholes are arranged outside the outline 2 of the tunnel face. The two boreholes are located in the third region 7 and the fourth region 8 outside the outline 2 of the tunnel face, respectively.

[0076] When using a tunnel boring machine (TBM) or shield tunneling method for excavation, the boreholes for horizontal directional drilling are positioned outside the tunnel face outline 2. The specific drilling operation procedure is as follows: First, starting from the tunnel face to be excavated, drill a hole at an oblique angle towards the outside of the tunnel face outline 2. Once the borehole reaches the predetermined position outside the outline 2, adjust the drill rod direction to make it parallel to the tunnel axis and continue extending the borehole. Through this operation method, the position 3 of the horizontal directional drilling can be positioned outside the tunnel face outline 2.

[0077] In an optional embodiment, in step S2, when the drill-and-blast method is used for excavation, the borehole position 3 of the horizontal directional drilling can be arranged in a circular area with a center radius of 2 meters at the tunnel face, and the specific number of boreholes is one or two.

[0078] In an optional implementation, in step S2, when the drill-and-blast method is used for excavation, such as Figure 2 As shown, borehole position 3 of the horizontal directional drilling can be arranged at the center of the tunnel face, and the number of boreholes is one.

[0079] In an optional implementation, in step S2, when the rock stratum 1 to be excavated is a rock stratum with its surface inclined to the left, such as Figure 8 As shown, the azimuth angles of the two borehole positions 3 can be β1 and β2, respectively. The formulas for calculating β1 and β2 are as follows:

[0080] β1 = 270° + α

[0081] β2=90°+α

[0082] α = arctan(ηtanγsinμ)

[0083] Wherein, β1 represents the azimuth angle when borehole position 3 is located to the upper left of the tunnel; β2 represents the azimuth angle when borehole position 3 is located to the lower right of the tunnel; α represents the apparent dip angle of the rock strata; η represents the ratio of the longitudinal scale to the transverse scale, wherein the longitudinal scale represents the ratio of the length in the vertical direction (i.e., the depth direction of the rock strata) on the cross-section to the vertical length of the actual geological body, and the transverse scale represents the ratio of the length in the horizontal direction on the cross-section to the horizontal length of the actual geological body; γ is the true dip angle of the rock strata; and μ is the angle between the strike of the rock strata and the tunnel face.

[0084] In an optional implementation, in step S2, when the rock stratum 1 to be excavated is a rock stratum with its surface inclined to the right, the azimuth angles of the two borehole positions 3 can be β3 and β4, respectively, and the calculation formulas for β3 and β4 are as follows:

[0085] β3=90°-α

[0086] β4=270°-α

[0087] α = arctan(ηtanγsinμ)

[0088] Wherein, β3 represents the azimuth angle when borehole position 3 is located to the upper right of the tunnel; β4 represents the azimuth angle when borehole position 3 is located to the lower left of the tunnel; α represents the apparent dip angle of the rock strata; η represents the ratio of the longitudinal scale to the transverse scale, wherein the longitudinal scale represents the ratio of the length in the vertical direction (i.e., the depth direction of the rock strata) on the cross-section to the vertical length of the actual geological body, and the transverse scale represents the ratio of the length in the horizontal direction on the cross-section to the horizontal length of the actual geological body; γ is the true dip angle of the rock strata; and μ is the angle between the strike of the rock strata and the tunnel face.

[0089] In an optional embodiment, in step S2, when a tunnel boring machine or shield tunneling method is used for excavation, the drilling position 3 of the horizontal directional drilling can be arranged 1 to 5 meters outside the outline 2 of the tunnel face, specifically 1 meter, 1.5 meters, 2 meters, 2.5 meters, 3 meters, 3.5 meters, 4 meters, 4.5 meters, and 5 meters outside the outline 2 of the tunnel face.

[0090] Example 2

[0091] This embodiment applies the tunnel horizontal directional drilling layout method described in Embodiment 1 to two engineering projects, thus constituting practical examples of Case 1 and Case 2.

[0092] Case 1

[0093] This case study illustrates a scenario where the rock stratum 1 to be excavated is a stratum whose bedding plane dips to the left. Figure 10 As shown, the ratio η between the longitudinal scale and the transverse scale in this project is 1. The tunnel lithology of this project is mostly hard rocks such as calcareous sandstone and limestone, which poses a risk of water inrush and mudslide. The overall integrity of the surrounding rock is relatively good, and the tunnel boring machine excavation method is adopted.

[0094] Using a compass, the strike of the rock stratum 1 to be excavated at the tunnel face is determined to be N35°E, the dip azimuth is 320°, the true dip angle γ is 40°, and the strike of the tunnel axis is N80°E. Based on the tunnel axis strike, the horizontal projection of the tunnel face is N10°W. Therefore, the angle between the rock stratum strike and the tunnel face is μ = 10° + 35° = 45°. The rock stratum dip direction refers to the direction indicated by the projection of a vertical line (inclination line) perpendicular to the strike line and downwards along the bedding plane onto the horizontal plane. The dip azimuth is the clockwise angle between the dip line and true north on the horizontal plane. Based on the above, it is determined that the rock stratum 1 to be excavated in this project is a rock stratum with the bedding plane dipping to the left. Therefore, two boreholes are arranged outside the tunnel face outline 2, with azimuths β1 and β2 at the two borehole positions 3. The calculation formulas for β1 and β2 are as follows:

[0095] β1 = 270° + α

[0096] β2=90°+α

[0097] α = arctan(ηtanγsinμ)

[0098] Among them, η=1, γ=40°, and μ=45°.

[0099] Therefore, α = arctan(1 × tan40° × sin45°) = 30°.

[0100] Therefore, β1=270°+α=270°+30°=300°, β2=90°+α=90°+30°=120°.

[0101] Based on the above calculations, two boreholes were drilled at azimuth angles of 120° and 300°, located 3 to 5 meters outside the tunnel face outline. After horizontal directional drilling, the borehole at 120° azimuth revealed the presence of soluble rocks such as limestone on the right side of the tunnel face. During drilling, a stream of water was observed, with a volume of approximately 50–60 m³. 3 / h. A borehole with an azimuth of 300° revealed the presence of calcareous sandstone on the left side of the tunnel face. Based on the rock strata's occurrence, the location of the current tunnel face and the soluble rock distribution ahead was inferred. In response to the presence of soluble rocks such as limestone and thread-like water outflows, two targeted drainage holes were promptly installed at the limestone distribution locations, gradually reducing the water volume. When excavation reached soluble rock strata such as limestone, a pneumatic drill (deepening borehole) detection scheme was promptly employed to conduct karst exploration around the tunnel and at the tunnel floor, accurately identifying the karst development around the tunnel, especially within a certain depth range at the tunnel floor.

[0102] The tunnel horizontal directional drilling layout method of this application can quantitatively arrange the drilling positions 3 when the rock stratum 1 to be excavated is a rock stratum with the bedding plane tilting to the left. It can accurately determine the distribution of soluble rock strata such as limestone in the tunnel and determine the water volume in front of the tunnel face, so as to play the function of targeted water drainage in advance, avoid adverse geological conditions such as water inrush and mudslide, ensure the safety of tunnel construction, improve the accuracy of exploration, reduce the number of drillings while ensuring continuous exploration, and significantly reduce exploration costs and save exploration cycle.

[0103] Case 2

[0104] This case study illustrates a scenario where the rock stratum to be excavated, stratum 1, is a rock stratum whose bedding plane dips to the right. Figure 11 As shown, the ratio η between the longitudinal scale and the transverse scale in this project is 1. The tunnel lithology in this project is mostly hard rocks such as granite and calcareous sandstone. There are alteration zones and compression fracture zones in some granite strata. The overall integrity of the surrounding rock is relatively good. The tunnel boring machine excavation method is adopted.

[0105] Using a compass, the strike of the rock stratum 1 to be excavated at the tunnel face was determined to be N35°W, the dip azimuth angle to be 40°, and the true dip angle γ to be 40°. The strike of the tunnel axis was N80°W. Based on the strike of the tunnel axis, the strike of the tunnel face projected onto the horizontal plane was determined to be N10°E. Therefore, the angle μ between the strike of the rock stratum and the tunnel face was μ = 10° + 35° = 45°. Based on the above, it was determined that the rock stratum 1 to be excavated in this project is a rock stratum with a bedding plane dipping to the right. Therefore, two boreholes were arranged outside the outline 2 of the tunnel face. The azimuth angles of the two borehole positions 3 were β3 and β4, respectively. The calculation formulas for β3 and β4 are as follows:

[0106] β3=90°-α

[0107] β4=270°-α

[0108] α = arctan(ηtanγsinμ)

[0109] Among them, η=1, γ=40°, and μ=45°.

[0110] Therefore, α = arctan(1 × tan40° × sin45°) = 30°.

[0111] Therefore, β3=90°-α=90°-30°=60°, β4=270°-α=270°-30°=240°.

[0112] Based on the above calculations, two boreholes were drilled at azimuth angles of 60° and 240°, 3m to 5m outside the tunnel face outline. After horizontal directional drilling, the borehole at 60° revealed an alteration zone 5m to 15m ahead of the tunnel face, with fractured surrounding rock, making it extremely prone to jamming, collapse, and delayed collapse with water inrush, posing a significant risk. The borehole at 240° revealed calcareous sandstone with relatively good surrounding rock integrity. Based on the rock strata's orientation, the location of the current tunnel face and the alteration zone ahead was inferred. Subsequently, grouting was used to promptly reinforce the alteration zone and other fractured surrounding rock areas. Once the surrounding rock strength met the requirements, the tunnel boring machine (TBM) successfully excavated through this section of alteration zone and fractured surrounding rock without experiencing any geological disasters such as jamming, collapse, or delayed collapse.

[0113] The tunnel horizontal directional drilling layout method of this application can quantitatively arrange the drilling positions 3 when the rock stratum 1 to be excavated is a rock stratum with the bedding plane tilting to the right, which improves the exploration accuracy, accurately detects the fractured areas of the surrounding rock such as the alteration zone in front of the tunnel face, avoids geological disasters such as machine jamming, collapse or delayed collapse, and improves construction efficiency; at the same time, while ensuring continuous exploration, it reduces the number of drillings, significantly reduces exploration costs and saves exploration time.

[0114] This application can be used for borehole layout in horizontal directional drilling of tunnels (caves) in mountainous areas such as railways, highways, or hydropower stations.

[0115] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for arranging horizontal directional boreholes in a tunnel, characterized in that, Includes the following steps: S1: Select tunnel excavation technology; S2: When the drill-and-blast method is used for excavation, the boreholes (3) of the horizontal directional drilling are arranged within the outline (2) of the tunnel face; When using a tunnel boring machine or shield tunneling method for excavation, the drilling location (3) of the horizontal directional drilling is arranged outside the outline (2) of the tunnel face. According to the rock strata attitude, the rock strata to be excavated (1) are divided into five categories: rock strata with rock strata dipped in the same direction as the tunnel axis, rock strata with rock strata bedding parallel to the horizontal plane, rock strata with rock strata bedding perpendicular to the horizontal plane, rock strata with rock strata bedding to the left and rock strata bedding to the right. When the rock stratum (1) to be excavated is a rock stratum whose dip direction is consistent with the tunnel axis, a borehole is arranged outside the outline (2) of the tunnel face, and the azimuth angle of the borehole position (3) is 90° or 270°. When the rock stratum to be excavated (1) is a rock stratum with the rock stratum surface parallel to the horizontal plane, two boreholes are arranged outside the outline (2) of the tunnel face, and the azimuth angles of the two borehole positions (3) are 0° and 180° respectively. When the rock stratum to be excavated (1) is a rock stratum with a bedding plane perpendicular to the horizontal plane, a borehole is arranged outside the outline (2) of the tunnel face, and the azimuth angle of the borehole position (3) is 90° or 270°. When the rock stratum (1) to be excavated is a rock stratum with its surface inclined to the left, two boreholes are arranged outside the outline (2) of the tunnel face, and the azimuth angles of the two borehole positions (3) are respectively β 1 and β 2, β 1 and β 2. The calculation formula is as follows: in, β 1 indicates the azimuth angle when the borehole location (3) is located to the upper left of the tunnel; β 2 indicates the azimuth angle when the borehole location (3) is located to the lower right of the tunnel; α Indicates the apparent dip angle of the rock strata; η The ratio of the vertical scale to the horizontal scale is indicated. The vertical scale represents the ratio of the length in the vertical direction (i.e., the depth direction of the rock strata) on the cross-section to the vertical length of the actual geological body. The horizontal scale represents the ratio of the length in the horizontal direction on the cross-section to the horizontal length of the actual geological body. γ The true dip angle of the rock strata; μ The angle between the rock strata strike and the tunnel face; When the rock stratum (1) to be excavated is a rock stratum with the stratum surface tilting to the right, two boreholes are arranged outside the outline (2) of the tunnel face, and the azimuth angles of the two borehole positions (3) are respectively β 3 and β 4, β 3 and β 4. The calculation formula is as follows: in, β 3 indicates the azimuth angle when the borehole location (3) is located to the upper right of the tunnel; β 4 indicates the azimuth angle when the borehole location (3) is located to the lower left of the tunnel; α Indicates the apparent dip angle of the rock strata; η The ratio of the vertical scale to the horizontal scale is indicated. The vertical scale represents the ratio of the length in the vertical direction (i.e., the depth direction of the rock strata) on the cross-section to the vertical length of the actual geological body. The horizontal scale represents the ratio of the length in the horizontal direction on the cross-section to the horizontal length of the actual geological body. γ The true dip angle of the rock strata; μ It is the angle between the rock strata strike and the tunnel face.

2. The method for arranging horizontal directional boreholes in a tunnel according to claim 1, characterized in that, In step S2, when the drill-and-blast method is used for excavation, the boreholes (3) of the horizontal directional drilling are arranged in a circular area with a radius of 2 meters at the center of the tunnel face.

3. The method for arranging horizontal directional boreholes in a tunnel according to claim 2, characterized in that, In step S2, when the drill-and-blast method is used for excavation, the borehole position (3) of the horizontal directional drilling is arranged at the center of the tunnel face.

4. A method for arranging horizontal directional boreholes in a tunnel according to any one of claims 1-3, characterized in that, In step S2, when a tunnel boring machine or shield tunneling method is used for excavation, the borehole position (3) of the horizontal directional drilling is arranged 1 to 5 meters outside the outline (2) of the tunnel face.

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