Novel prestressed truss anchor cable system and using method thereof

Abstract

The invention relates to a novel prestress truss anchor cable system and a using method thereof, the novel prestress truss anchor cable system is mainly applied to the field of coal mine roadway supporting, the novel prestress truss anchor cable system comprises a truss device, cable-stayed anchor cables and vertical anchor cables, the novel prestress truss anchor cable system is axially and symmetrically arranged along the axial direction of a roadway, one cable-stayed anchor cable is arranged on each side, and the vertical anchor cables are located in the middle; the truss device is composed of a joist and a special-shaped supporting plate, the special-shaped supporting plate is composed of a flat steel plate, a right-angle triangular block and an inclined anchor cable hole, side anchor cable holes are formed in the two ends of the joist in the length direction, and a middle anchor cable hole is formed in the middle. An extrusion stress area in the horizontal direction is formed on the roadway roof, the overall performance of the roof supporting structure is improved, extrusion stress in the horizontal direction is formed in the roadway roof, extrusion force is applied to the roadway roof in the vertical direction, and the overall performance of the roof supporting structure is greatly improved.

Description

Technical Field

[0001] This invention relates to a novel prestressed truss anchor cable system and its application method, which is mainly used in the field of coal mine roadway support. Background Technology

[0002] As mining depth increases, the surrounding rock environment deteriorates, leading to severe deformation in some areas. Anchor cable support is a crucial support method in mining engineering for achieving surrounding rock stability and ensuring safe production. Traditional anchor cable support structures for roadway roofs are isolated point supports, unable to apply significant active prestress to the roof, and the anchor points are located in the easily delaminating zone at the top of the roadway, increasing the risk of roof collapse. Extensive research and engineering practice have demonstrated that prestressed truss anchor cable support technology is an effective technique for controlling deformation in deep roadways. This technology uses a truss and specialized locking devices to connect two inclined anchor cables, then applies high prestress to both cables simultaneously, creating a horizontal compressive stress zone within the roadway roof, thus improving the overall performance of the roof support structure. Traditional truss anchor cable support technology mainly uses truss connectors and anchor cable locks to connect two anchor cables, and then applies high preload to the two anchor cables (such as a lateral rooted anchor cable truss support structure disclosed in Chinese Patent Application No. CN202021364426.2, a high prestressed anchor cable self-locking connection device that is easy to install in Chinese Patent Application No. CN201520578871.1, a set of high prestressed truss anchor cable connection devices that are easy to tension and lock in Chinese Patent Application No. CN201420738580.X, a double anchor cable joint locking device and method therein in Chinese Patent Application No. CN201310395658.2, and an anchor cable truss prevention method for roof collapse and side collapse in coal roadways in Chinese Patent Application No. CN201010196509.X) in Chinese Patent Application No. CN201010196509.X). However, due to the influence of the reverse tension, a pair of unidirectional couples are generated on the connector. The size of the external anchor cable lock affects the cross-sectional size of the connector, resulting in a large couple value. This causes the connector to rotate in the plane, causing the anchor cable to change from a state of tensile stress to a state of tensile and shear stress. This greatly affects the performance of the anchor cable and truss, weakens the compressive stress on the roadway roof, and causes a sharp drop in the support effect, which in turn significantly increases the risk of roof collapse.

[0003] In addition, in the existing technology, a series of technical improvements have been made to the traditional prestressed truss anchor cable support technology. For example: (1) Chinese patent application No. CN201711307701.X discloses a roadway sliding rail type truss anchor cable support method and support device. The present invention can control the extension and retraction of the sliding rail type telescopic truss according to the magnitude of the horizontal force generated by the horizontal movement of the roadway roof to adjust the horizontal compressive stress of the sliding rail type telescopic truss, so that the horizontal compressive stress balances the horizontal force, so as to adapt to or suppress the horizontal compression slippage or loosening expansion deformation of the roadway roof. However, the sliding rail structure of the device is relatively fragile. It is difficult to withstand the pressure generated by the roadway roof and is easily damaged. In addition, the roadway is relatively humid, which can easily cause the sliding drive device in the invention to rust and fail. (2) Chinese patent application No. CN201711307702.4 discloses a method and device for large-scale support of roadway truss anchor cable. The device connects multiple telescopic trusses through truss combination components, and anchors the truss combination components with vertical anchor cables and anchors multiple telescopic trusses with multiple inclined anchor cables to form a large-scale support for the roadway roof. However, the structure of the invention device is complex, difficult to install on site, and the support time is long, which increases the on-site labor cost. Summary of the Invention

[0004] In order to overcome the defects in existing truss anchor cable support technology, this invention provides a novel prestressed truss anchor cable system and its application method.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A novel prestressed truss anchor cable system is characterized by comprising a truss assembly, inclined anchor cables, and vertical anchor cables. The system is axially symmetrically arranged along the roadway axis, with one inclined anchor cable on each side and a vertical anchor cable located in the middle. The truss assembly consists of a support beam and a shaped support plate. The shaped support plate is composed of a flat steel plate, a right-angled triangular block, and inclined anchor cable holes. The flat steel plate is located above the right-angled triangular block and connected by welding. One end of each inclined anchor cable hole is located in the middle of the inclined surface of the right-angled triangular block, and the other end overlaps with the side anchor cable hole. The length of the support beam is less than the width of the roadway, and side anchor cable holes are provided at both ends of the support beam along its length, with a central anchor cable hole provided in the middle.

[0007] Furthermore, the distance L1 from the side anchor cable hole to the centerline of the roadway is generally B / 3 (B is the width of the roadway);

[0008] Furthermore, both the side anchor cable holes and the middle anchor cable holes are elongated elliptical holes;

[0009] Furthermore, the inclination angle of the inclined anchor cable hole is determined by the installation angle of the inclined anchor cable, and the diameter of the inclined anchor cable hole is larger than the diameter of the inclined anchor cable;

[0010] Furthermore, the flat steel plate and the right-angled triangular block are made of high-strength steel, the width of the flat steel plate and the width of the right-angled triangular block are equal to the inner width of the support beam, the support beam is preferably made of JM steel strip, and the special-shaped support plate is connected to the support beam by welding.

[0011] Furthermore, the angle α between the inclined anchor cable and the vertical direction is 15-35°, the vertical anchor cable is perpendicular to the roof, and both the inclined anchor cable and the vertical anchor cable are conventional anchor cables for coal mine roadway support.

[0012] Furthermore, the present invention provides a method for using a novel prestressed truss anchor cable system, and the on-site implementation parameter determination includes the following steps:

[0013] (1) Determination of the inter-hole offset d

[0014] This invention provides a novel prestressed truss anchor cable system. Compared to traditional truss anchor cable systems, the distance between the side anchor cable hole and the roadway centerline is smaller than the distance between the inclined anchor cable installation hole and the roadway centerline. A certain misalignment distance (i.e., hole misalignment d) exists between them, which can be obtained using equation (1). The actual function of this misalignment distance is that after the truss device and the two inclined anchor cables are installed, when the two inclined anchor cables are mechanically tensioned simultaneously, the support beam is stretched laterally, causing the side anchor cable hole to coincide with the inclined anchor cable installation hole. This constrains the roadway roof, forming a horizontal compressive stress zone in the roadway roof, thus improving the overall performance of the roof support structure.

[0015] d = l z ·η y (1)

[0016] L z =L x1 +L x2 (2)

[0017] In the formula, d is the inter-hole offset in meters; l z η is the length of the free end of the stay cable, in meters; y The elongation rate of the inclined anchor cable is generally taken as 1%; L x1 The distance from the inclined anchor cable installation hole to the roadway sidewall can be obtained by equation (5); L x2 The length of the inclined anchor cable above the plastic zone of the surrounding rock in the tunnel can be obtained by formula (6).

[0018] (2) The distance L2 from the installation hole of the inclined anchor cable to the centerline of the roadway, and the length L of the inclined anchor cable. x The length L of the vertical anchor cable z The determination

[0019] This invention provides a novel method for using a prestressed truss anchor cable system. The truss device, the inclined anchor cables, and the vertical anchor cables apply lateral and vertical prestressing forces to the roadway roof, forming a pressure arch in the roadway roof, thereby improving the overall performance of the roof support structure. The main parameters of this novel prestressed truss anchor cable system include: the distance L2 between the inclined anchor cable installation hole and the roadway centerline, and the length L of the inclined anchor cable. x The length L of the vertical anchor cable z .

[0020] (a) Distance L2 between the inclined anchor cable installation hole and the centerline of the roadway

[0021] The distance L2 between the inclined anchor cable installation hole and the centerline of the roadway can be obtained by formula (3).

[0022] L2 = L1 + d (3)

[0023] In the formula, L2 is the distance from the inclined anchor cable installation hole to the roadway centerline, m; L1 is the distance from the side anchor cable hole to the roadway centerline, m; d is the offset between holes, m.

[0024] (b) Length L of the inclined anchor cable x

[0025] To ensure the overall stability of the novel prestressed truss anchor cable system, the anchoring end of the inclined anchor cable should be located deep within the triaxially compressed rock mass of the roadway shoulder, where it is not easily damaged. For ease of calculation, the length of the inclined anchor cable is divided into L... x1 L x2 L x3 L x4 L x5 It consists of five parts, of which L x1 L is the distance from the inclined anchor cable installation hole to the roadway sidewall. x2 L is the length of the inclined anchor cable above the plastic zone of the surrounding rock in the tunnel. x3 L is the length from the end of the inclined anchor cable to the boundary of the plastic zone. x4 Let d be the inter-hole offset, and L be the inter-hole offset. x5 The length L of the inclined anchor cable can be obtained by summing the length of the inclined anchor cable hole and the exposed length of the inclined anchor cable. x :

[0026] L x =L x1 +L x2 +L x3 +L x4 +L x5 (4)

[0027] L x1 The distance from the inclined anchor cable installation hole to the roadway sidewall can be obtained by formula (5).

[0028]

[0029] In the formula, α is the angle between the inclined anchor cable and the vertical direction.

[0030] L x2 The length of the inclined anchor cable above the plastic zone of the surrounding rock in the roadway can be obtained through equations (6) and (7).

[0031] L x2 =x0 / sinα (6)

[0032]

[0033] In the formula, K is the stress concentration factor; p1 is the roadway side support resistance; m is the roadway height; and c is the cohesion of the coal body. ξ is the internal friction angle of the coal seam; f is the friction coefficient of the contact surface between the coal seam and the roof and floor; ξ is the triaxial stress coefficient.

[0034] L x3 The distance from the end of the inclined anchor cable to the boundary of the plastic zone can be obtained by equation (8).

[0035]

[0036] In the formula, K1 is the safety factor, which is generally taken as 2; d1 is the diameter of the inclined anchor cable; f a f is the tensile strength of the cable-stayed anchor; c This refers to the bond strength between the inclined anchor cable and the anchoring agent.

[0037] L x4 The inter-hole offset d can be obtained by equation (1).

[0038] L x5 The length of the inclined anchor cable hole and the exposed length of the inclined anchor cable are the sum of the length of the inclined anchor cable, which is generally taken as 300-400mm.

[0039] (c) Vertical anchor cable length L z

[0040] The length L of the vertical anchor cable z Equal to the length L of the inclined anchor cable x .

[0041] The present invention provides a method for using a novel prestressed truss anchor cable system, the on-site implementation of which includes the following steps:

[0042] First, after the tunnel excavation is completed, first lay the anchor mesh on the roof, and then, according to the calculation result of formula (2), drill one inclined anchor cable installation hole on each side of the central axis of the tunnel roof. The depth of the inclined anchor cable installation hole is L.x1 +L x2 +L x3 The diameter of the mounting hole for the inclined anchor cable is larger than the diameter of the inclined stay anchor cable.

[0043] The second step is to first place the truss device symmetrically along the central axis of the tunnel, and then pass the two inclined anchor cables through the inclined anchor cable holes in the special-shaped support plate and the side anchor cable holes in the support beam from bottom to top. The inclined anchor cables are anchored with anchoring agent, and the exposed ends of the inclined anchor cables are locked with locks. Finally, the two inclined anchor cables are mechanically tensioned at the same time to apply preload.

[0044] The third step is to drill a center anchor cable installation hole at the location of the center anchor cable hole in the supporting beam. The depth of the center anchor cable installation hole is L. x1 +L x2 +L x3 +L x4 The diameter of the middle anchor cable mounting hole is larger than the diameter of the vertical anchor cable.

[0045] Step 4: Pass the vertical anchor cable through the anchor cable tray and the middle anchor cable hole from bottom to top, anchor the vertical anchor cable with anchoring agent, lock the exposed end of the vertical anchor cable with a lock, and mechanically tension the vertical anchor cable to apply preload.

[0046] Fifth, install the new type of prestressed truss anchor cable device sequentially along the direction of the roadway at intervals L3, following the steps from the first to the fourth step, where L3 is generally 1500-3000mm.

[0047] The beneficial effects of this invention are as follows:

[0048] (1) The present invention provides a novel prestressed truss anchor cable system. Compared with the traditional truss anchor cable system, the distance between the side anchor cable hole and the roadway centerline is smaller than the distance between the inclined anchor cable installation hole and the roadway centerline, and there is a certain misalignment distance between the two. The actual function of the misalignment distance is: after the truss device and the inclined anchor cables on both sides are installed, when the two inclined anchor cables are mechanically tensioned, the support beam is stretched laterally, so that the side anchor cable hole and the inclined anchor cable installation hole coincide, thereby constraining the roadway roof and forming a horizontal compressive stress zone in the roadway roof, improving the overall performance of the roof support structure.

[0049] (2) A novel prestressed truss anchor cable system of this invention adds vertical anchor cables on the basis of prestressed inclined anchor cables. In addition to forming horizontal compressive stress in the roadway roof, it also applies vertical compressive force to the roadway roof, which greatly improves the overall performance of the roof support structure.

[0050] (3) The present invention patent provides a novel prestressed truss anchor cable system, which makes full use of the flexibility of anchor cable construction, and has the advantages of short installation period, strong prestress, safety and reliability and cost saving, thereby improving the truss's support capacity for deep roadways.

[0051] (4) The truss device of this invention integrates the support beam and the special-shaped support plate into a single structure. It has a simple structure, is easy to process, convenient to use, safe and reliable, and has good stability. It can avoid the risk of roadway collapse caused by connector failure in traditional truss anchor cable devices. Attached Figure Description

[0052] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0053] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0054] Figure 2 This is an overall drawing of the truss device of the present invention;

[0055] Figure 3 This is a top view of the truss device of the present invention;

[0056] Figure 4 This is a left view of the truss device of the present invention;

[0057] Figure 5 This is an overall drawing of the support beam of the present invention;

[0058] Figure 6 This is an overall drawing of the irregular-shaped pallet of the present invention;

[0059] Figure 7 This is a schematic diagram of the misalignment distance between the inclined anchor cable mounting hole and the side anchor cable hole of the present invention;

[0060] Figure 8 This is a schematic diagram illustrating the determination of the length of the inclined anchor cable according to the present invention;

[0061] Figure 9 This is a schematic diagram of the first step of on-site installation of the present invention;

[0062] Figure 10 This is a schematic diagram of the second step of the on-site installation of the present invention;

[0063] Figure 11 This is a schematic diagram of the third step of the on-site installation of the present invention;

[0064] Figure 12 This is a schematic diagram of the fourth step of the on-site installation of the present invention.

[0065] Figure label:

[0066] 1- Truss assembly; 2- Inclined anchor cable; 3- Vertical anchor cable; 4- Support beam; 41- Side anchor cable hole; 42- Center anchor cable hole; 5- Irregular support plate; 51- Flat steel plate; 52- Right-angled triangular block; 53- Inclined anchor cable hole; 6- Roadway; 7- Roadway centerline; 8- Roof plate; 9- Inclined anchor cable installation hole; 10- Lock; 11- Center anchor cable installation hole; 12- Anchor cable tray; 13- Roadway side; 14- Plastic zone. Detailed Implementation

[0067] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0068] See Figure 1 As shown, a novel prestressed truss anchor cable system is characterized by comprising a truss device 1, inclined anchor cables 2, and vertical anchor cables 3. The novel prestressed truss anchor cable system is arranged symmetrically along the roadway axis, with one inclined anchor cable 2 on each side and the vertical anchor cable 3 located in the middle.

[0069] See Figures 2-4 As shown, the truss device 1 consists of a support beam 4 and a special-shaped support plate 5;

[0070] Figure 5 This is a schematic diagram of the support beam of the present invention. As can be seen from the figure, the length of the support beam 4 is less than the width of the roadway 6. Side anchor cable holes 41 are opened at both ends of the length direction of the support beam 4, and a middle anchor cable hole 42 is opened in the middle. The distance L1 between the side anchor cable hole 41 and the center axis 7 of the roadway is generally B / 3 (B is the width of the roadway 6). Both the side anchor cable hole 41 and the middle anchor cable hole 42 are elongated elliptical holes. The support beam 4 is preferably made of JM steel strip.

[0071] Figure 6 This is a schematic diagram of the irregular-shaped support plate of the present invention. As can be seen from the diagram, the irregular-shaped support plate 5 comprises a flat steel plate 51, a right-angled triangular block 52, and an inclined anchor cable hole 53. The flat steel plate 51 is located above the right-angled triangular block 52 and is connected by welding. One end of the inclined anchor cable hole 53 is located in the middle of the inclined surface of the right-angled triangular block 52, and the other end overlaps with the side anchor cable hole 41. The inclination angle of the inclined anchor cable hole 53 is determined by the installation angle of the inclined anchor cable 2. The diameter of the inclined anchor cable hole 53 is larger than the diameter of the inclined anchor cable 2. The flat steel plate 51 and the right-angled triangular block 52 are made of high-strength steel. The width of the flat steel plate 51 and the width of the right-angled triangular block 52 are equal to the inner width of the support beam 4. The irregular-shaped support plate 5 and the support beam 4 are connected by welding.

[0072] Both the inclined anchor cable 2 and the vertical anchor cable 3 are conventional anchor cables for coal mine roadway support.

[0073] The angle α between the inclined anchor cable 2 and the vertical direction is 15-35°, and the vertical anchor cable 3 is perpendicular to the top plate 8.

[0074] The present invention provides a method for using a novel prestressed truss anchor cable system, and the determination of on-site implementation parameters includes the following steps:

[0075] (1) Determination of the inter-hole offset d

[0076] See Figure 7 As shown, the present invention provides a novel prestressed truss anchor cable system. Compared with the traditional truss anchor cable system, the distance between the side anchor cable hole 41 and the roadway centerline 7 is smaller than the distance between the inclined anchor cable installation hole 9 and the roadway centerline 7. There is a certain misalignment distance (i.e., hole misalignment d) between them. The hole misalignment distance d can be obtained by formula (1). The actual function of the misalignment distance is: after the truss device 1 and the two inclined anchor cables 2 are installed, when the two inclined anchor cables 2 are mechanically tensioned, the support beam 4 is stretched laterally, so that the side anchor cable hole 41 coincides with the inclined anchor cable installation hole 9, thereby constraining the roadway roof 8 and forming a horizontal compressive stress zone in the roadway roof 8, improving the overall performance of the roof support structure.

[0077] d = l z ·η y (1)

[0078] L z =L x1 +L x2 (2)

[0079] In the formula, d is the inter-hole offset in meters; l z η is the length of the free end of the stay cable, in meters; y The elongation rate of the inclined anchor cable 2 is generally taken as 1%; L x1 The distance from the inclined anchor cable installation hole 9 to the roadway sidewall 13 can be obtained by formula (5); L x2 The length of the inclined anchor cable above the plastic zone 14 of the surrounding rock of the tunnel can be obtained by formula (6).

[0080] (2) The distance L2 between the inclined anchor cable installation hole 9 and the roadway centerline 7, and the length L of the inclined anchor cable 2 x The vertical anchor cable 3 has a length L. z The determination

[0081] See Figure 8 As shown, this invention provides a novel prestressed truss anchor cable system. The system utilizes the truss device 1, the inclined anchor cables 2, and the vertical anchor cables 3 to apply lateral and vertical prestressing forces to the roadway roof 8, forming a pressure arch on the roadway roof 8, thereby improving the overall performance of the roof support structure. The main parameters of this novel prestressed truss anchor cable system include: the distance L2 between the inclined anchor cable installation hole 9 and the roadway centerline 7, and the length L of the inclined anchor cable 2.x The vertical anchor cable 3 has a length L. z .

[0082] (a) Distance L2 between inclined anchor cable installation hole 9 and the roadway centerline 7

[0083] The distance L2 between the inclined anchor cable installation hole 9 and the roadway centerline 7 can be obtained by formula (3).

[0084] L2 = L1 + d (3)

[0085] In the formula, L2 is the distance from the inclined anchor cable installation hole 9 to the roadway centerline 7, in meters; L1 is the distance from the side anchor cable hole 41 to the roadway centerline 7, in meters; and d is the stagger distance between holes, in meters.

[0086] (b) Length L of the inclined anchor cable 2 x

[0087] To ensure the overall stability of the novel prestressed truss anchor cable system, the anchoring end of the inclined anchor cable 2 should be located deep within the triaxially compressed rock mass of the roadway shoulder, where it is not easily damaged. For ease of calculation, the length of the inclined anchor cable 2 is divided into L... x1 L x2 L x3 L x4 L x5 It consists of five parts, of which L x1 L is the distance from the inclined anchor cable installation hole 9 to the roadway sidewall 13. x2 L is the length of the inclined anchor cable above the plastic zone 14 of the surrounding rock in the tunnel. x3 L is the length from the end of the inclined anchor cable to the boundary of the plastic zone 14. x4 Let d be the inter-hole offset, and L be the inter-hole offset. x5 The length L of the inclined anchor cable 2 is the sum of the length of the inclined anchor cable hole 53 and the exposed length of the inclined anchor cable 2. x :

[0088] L x =L x1 +L x2 +L x3 +L x4 +L x5 (4)

[0089] L x1 The distance from the inclined anchor cable installation hole 9 to the roadway sidewall 13 can be obtained by formula (5).

[0090]

[0091] In the formula, α is the angle between the inclined anchor cable 2 and the vertical direction.

[0092] L x2The length of the inclined anchor cable 2 above the plastic zone 14 of the surrounding rock of the tunnel can be obtained by formula (6) and formula (7).

[0093] L x2 =x0 / sinα (6)

[0094]

[0095] In the formula, K is the stress concentration factor; p1 is the support resistance of roadway 13; m is the height of roadway 6; and c is the cohesion of the coal body. ξ is the internal friction angle of the coal seam; f is the friction coefficient of the contact surface between the coal seam and the roof and floor; ξ is the triaxial stress coefficient.

[0096] L x3 The distance from the end of the inclined anchor cable to the boundary of the plastic zone 14 can be obtained by equation (8).

[0097]

[0098] In the formula, K1 is the safety factor, which is generally taken as 2; d1 is the diameter of the inclined anchor cable 2; f a f is the tensile strength of the inclined anchor cable 2; c The bond strength between the inclined anchor cable 2 and the anchoring agent.

[0099] L x4 The inter-hole offset d can be obtained by equation (1).

[0100] L x5 The length of the inclined anchor cable hole 53 is the sum of the exposed length of the inclined anchor cable 2, which is generally taken as 300-400mm.

[0101] (c) Vertical anchor cable length L z

[0102] The length L of the vertical anchor cable z Equal to the length L of the inclined anchor cable x .

[0103] The present invention provides a method for using a novel prestressed truss anchor cable system, the on-site implementation of which includes the following steps:

[0104] Figure 9 This is a schematic diagram of the first step of the on-site installation of the present invention. After the tunnel 6 is excavated, an anchor mesh is first laid on the roof 8, and then, according to the calculation result of formula (2), one inclined anchor cable installation hole 9 is drilled on each side of the central axis 7 of the tunnel roof. The depth of the inclined anchor cable installation hole 9 is L. x1 +L x2 +L x3 The diameter of the inclined anchor cable mounting hole 9 is larger than the diameter of the inclined anchor cable 2.

[0105] Figure 10 This is a schematic diagram of the second step of the on-site installation of the present invention. First, the truss device 1 is placed symmetrically along the central axis 7 of the tunnel. Then, the two inclined anchor cables 2 are passed from bottom to top through the inclined anchor cable holes 53 in the irregular support plate 5 and the side anchor cable holes 41 in the support beam 2. The inclined anchor cables 2 are anchored using anchoring agent. The exposed ends of the inclined anchor cables 2 are locked with locking devices 10. Finally, the two inclined anchor cables 2 are mechanically tensioned simultaneously to apply preload.

[0106] Figure 11 This is a schematic diagram of the third step of the on-site installation of the present invention. A middle anchor cable installation hole 11 is drilled at the position of the anchor cable hole 42 in the supporting beam, and the depth of the middle anchor cable installation hole 11 is L. x1 +L x2 +L x3 +L x4 The diameter of the middle anchor cable mounting hole 11 is larger than the diameter of the vertical anchor cable 3.

[0107] Figure 12 This is a schematic diagram of the fourth step of the on-site installation of the present invention. The vertical anchor cable 3 is passed through the anchor cable tray 12 and the central anchor cable hole 42 from bottom to top. The vertical anchor cable 3 is anchored using an anchoring agent. The exposed end of the vertical anchor cable 3 is locked with a locking device 10. The vertical anchor cable 3 is mechanically tensioned to apply a preload.

[0108] Fifth, install the new type of prestressed truss anchor cable device sequentially along the direction of roadway 6 at intervals of L3, following the steps from the first to the fourth step, where L3 is generally 1500-3000mm.

[0109] The beneficial effects of this invention are as follows:

[0110] (1) The present invention provides a novel prestressed truss anchor cable system. Compared with the traditional truss anchor cable system, the distance between the side anchor cable hole 41 and the roadway centerline 7 is smaller than the distance between the inclined anchor cable installation hole 53 and the roadway centerline 7, and there is a certain misalignment distance between them. The actual function of the misalignment distance is: after the truss device 1 and the two inclined anchor cables 2 are installed, when the two inclined anchor cables 2 are mechanically tensioned, the support beam 4 is stretched laterally, so that the side anchor cable hole 41 coincides with the inclined anchor cable installation hole 9, thereby constraining the roadway roof 8, forming a horizontal compressive stress zone in the roadway roof 8, and improving the overall performance of the roof support structure.

[0111] (2) A novel prestressed truss anchor cable system of this invention adds a vertical anchor cable 3 to the prestressed inclined anchor cable 2. In addition to forming horizontal compressive stress in the roadway roof 8, it also applies vertical compressive force to the roadway roof 8, which greatly improves the overall performance of the roof 8 support structure.

[0112] (3) The present invention patent provides a novel prestressed truss anchor cable system, which makes full use of the flexibility of anchor cable construction, and has the advantages of short installation period, strong prestress, safety and reliability and cost saving, thereby improving the truss's support capacity for deep roadways.

[0113] (4) The truss device 1 of this invention integrates the support beam 4 and the irregular support plate 5 into one structure. It has a simple structure, is easy to process, convenient to use, safe and reliable, and has good stability. It can avoid the risk of roadway collapse caused by connector failure in traditional truss anchor cable devices.

[0114] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions conceived without inventive effort should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A novel prestressed truss anchor cable system, characterized in that, It includes a truss assembly, inclined anchor cables, and vertical anchor cables. The novel prestressed truss anchor cable system is arranged symmetrically along the roadway axis, with one inclined anchor cable on each side and a vertical anchor cable located in the middle. The truss assembly consists of a support beam and a special-shaped support plate. The special-shaped support plate consists of a flat steel plate, a right-angled triangular block, and inclined anchor cable holes. The flat steel plate is located above the right-angled triangular block and is connected by welding. One end of the inclined anchor cable hole is located in the middle of the inclined surface of the right-angled triangular block, and the other end overlaps with the side anchor cable hole. The length of the support beam is less than the width of the roadway. Side anchor cable holes are opened at both ends of the support beam along its length, and a middle anchor cable hole is opened in the middle.

2. The novel prestressed truss anchor cable system according to claim 1, characterized in that, The distance between the side anchor cable hole and the centerline of the roadway is generally one-third of the roadway width.

3. The novel prestressed truss anchor cable system according to claim 1, characterized in that, Both the side anchor cable holes and the middle anchor cable holes are elongated elliptical holes.

4. The novel prestressed truss anchor cable system according to claim 1, characterized in that, The inclination angle of the inclined anchor cable hole is determined by the installation angle of the inclined anchor cable, and the diameter of the inclined anchor cable hole is larger than the diameter of the inclined anchor cable.

5. A novel prestressed truss anchor cable system according to claim 1, characterized in that, The flat steel plate and the right-angled triangular block are made of high-strength steel. The width of the flat steel plate and the width of the right-angled triangular block are equal to the inner width of the support beam. The support beam is preferably made of JM steel strip. The irregular-shaped support plate is connected to the support beam by welding.

6. A novel prestressed truss anchor cable system according to claim 1, characterized in that, The angle α between the inclined anchor cable and the vertical direction is 15-35°, and the vertical anchor cable is perpendicular to the roof. Both the inclined anchor cable and the vertical anchor cable are conventional anchor cables for coal mine roadway support.

7. A novel prestressed truss anchor cable system according to claim 1, characterized in that, The present invention provides a method for using a novel prestressed truss anchor cable system, and the determination of on-site implementation parameters includes the following steps: (1) Determination of the inter-hole offset d The present invention provides a novel prestressed truss anchor cable system. Compared with the traditional truss anchor cable system, the distance between the side anchor cable hole and the roadway centerline is smaller than the distance between the inclined anchor cable installation hole and the roadway centerline. There is a certain misalignment distance (i.e., hole misalignment d) between the two. The hole misalignment d can be obtained by equation (1). d=l z ·or y (1) L z =L x1 +L x2 (2) In the formula, d is the inter-hole offset, in meters; l z η is the length of the free end of the stay cable, in meters (m). y The elongation rate of the inclined anchor cable is generally taken as 1%; L x1 The distance from the inclined anchor cable installation hole to the roadway sidewall can be obtained by equation (5); L x2 The length of the inclined anchor cable above the plastic zone of the surrounding rock in the roadway can be obtained by formula (6); (2) The distance L2 from the installation hole of the inclined anchor cable to the centerline of the roadway, and the length L of the inclined anchor cable. x The length L of the vertical anchor cable z Determination: (a) Distance L2 between the inclined anchor cable installation hole and the centerline of the roadway The distance L2 between the inclined anchor cable installation hole and the roadway centerline can be obtained by formula (3); L2 = L1 + d (3) In the formula, L2 is the distance from the inclined anchor cable installation hole to the roadway centerline, in meters; L1 is the distance from the side anchor cable hole to the roadway centerline, in meters; and d is the offset between holes, in meters. (b) Length L of the inclined anchor cable x To ensure the overall stability of the novel prestressed truss anchor cable system, the anchoring end of the inclined anchor cable should be located in a triaxially compressed rock mass deep within the roadway shoulder that is not easily damaged. For ease of calculation, the length of the inclined anchor cable is divided into L... x1 L x2 L x3 L x4 L x5 It consists of five parts, of which L x1 L is the distance from the inclined anchor cable installation hole to the roadway sidewall. x2 L is the length of the inclined anchor cable above the plastic zone of the surrounding rock in the tunnel. x3 L is the length from the end of the inclined anchor cable to the boundary of the plastic zone. x4 Let d be the inter-hole offset, and L be the inter-hole offset. x5 The length L of the inclined anchor cable can be obtained by summing the length of the inclined anchor cable hole and the exposed length of the inclined anchor cable. x : L x =L x1 +L x2 +L x3 +L x4 +L x5 (4) L x1 The distance from the inclined anchor cable installation hole to the roadway sidewall can be obtained by formula (5); In the formula, α is the angle between the inclined anchor cable and the vertical direction; L x2 The length of the inclined anchor cable above the plastic zone of the surrounding rock in the roadway can be obtained by formula (6) and formula (7); L x2 =x0 / sinα (6) In the formula, K is the stress concentration factor; p1 is the roadway side support resistance; m is the roadway height; and c is the cohesion of the coal body. ξ is the internal friction angle of the coal seam; f is the friction coefficient of the contact surface between the coal seam and the roof and floor; ξ is the triaxial stress coefficient. L x3 The distance from the end of the inclined anchor cable to the boundary of the plastic zone can be obtained by equation (8); In the formula, K1 is the safety factor, which is generally taken as 2; d1 is the diameter of the inclined anchor cable; f a f is the tensile strength of the cable-stayed anchor; c The bond strength between the inclined anchor cable and the anchoring agent; L x4 The inter-hole offset d can be obtained by equation (1); L x5 The sum of the length of the inclined anchor cable hole and the exposed length of the inclined anchor cable is generally taken as 300-400mm; (c) Vertical anchor cable length L z The length L of the vertical anchor cable z Equal to the length L of the inclined anchor cable x ; The present invention provides a method for using a novel prestressed truss anchor cable system, the on-site implementation of which includes the following steps: First, after the tunnel excavation is completed, first lay the anchor mesh on the roof, and then, according to the calculation result of formula (2), drill one inclined anchor cable installation hole on each side of the central axis of the tunnel roof. The depth of the inclined anchor cable installation hole is L. x1 +L x2 +L x3 The diameter of the inclined anchor cable mounting hole is larger than the diameter of the inclined anchor cable; The second step is to first place the truss device symmetrically along the central axis of the tunnel, and then pass the two inclined anchor cables through the inclined anchor cable holes in the special-shaped support plate and the side anchor cable holes in the support beam from bottom to top. The inclined anchor cables are anchored with anchoring agent, and the exposed ends of the inclined anchor cables are locked with locks. Finally, the two inclined anchor cables are mechanically tensioned at the same time to apply preload. The third step is to drill a center anchor cable installation hole at the location of the center anchor cable hole in the supporting beam. The depth of the center anchor cable installation hole is L. x1 +L x2 +L x3 +L x4 The diameter of the middle anchor cable mounting hole is larger than the diameter of the vertical anchor cable. Step 4: Pass the vertical anchor cable through the anchor cable tray and the middle anchor cable hole from bottom to top, anchor the vertical anchor cable with anchoring agent, lock the exposed end of the vertical anchor cable with a lock, and mechanically tension the vertical anchor cable to apply preload. Fifth, install the new type of prestressed truss anchor cable device sequentially along the direction of the roadway at intervals L3, following the steps from the first to the fourth step, where L3 is generally 1500-3000mm.

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