A method for constructing an outer self-bearing ring and a near-surface yielding supporting ring in a roadway surrounding rock fracture ring

Abstract

A roadway surrounding rock fracturing ring construction outer self-bearing ring and near surface yielding support ring collaborative control method belongs to the technical field of mineral exploitation, and comprises the following steps: the fracturing target rock stratum meeting the physical and mechanical parameters is probed around the roadway; the surrounding rock loose ring characteristic parameter is determined, and then the near surface yielding support ring range is determined; the pulse fracturing borehole length is determined according to the target fracturing rock stratum, and the pulse fracturing weakening ring range is obtained; the rock stratum outside the yielding support ring is weakened by the pulse fracturing mode to form the pulse fracturing weakening ring, at the same time, the high support stress of the surrounding rock in the pulse fracturing weakening ring is transferred to the far field hard rock stratum, and the far field surrounding rock outer self-bearing ring is constructed; the near surface yielding support ring is constructed through the active and passive yielding support modes, and the buffer zone is formed between the yielding support ring and the pulse fracturing weakening ring; through the collaborative control mode of the roadway surrounding rock fracturing weakening-far field surrounding rock self-bearing-near surface surrounding rock yielding support, the deep well soft rock roadway surrounding rock large deformation control is realized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of mineral exploitation, and particularly relates to a method for constructing an outer self-bearing circle and a near-surface yielding supporting circle in cooperation to control a roadway surrounding rock. BACKGROUND

[0002] With the gradual development of coal mining in China towards the deep part, the high ground stress environment has a significant impact on the roadway surrounding rock. Under the deep high ground stress environment, the roadway surrounding rock appears rheological and structural instability and other large deformation phenomena, which specifically show the characteristics of "large deformation of roadway surrounding rock, long duration, and serious damage of supporting structure", which seriously affects the safety and efficient production of underground mines.

[0003] Under the condition of deep mining, the ground stress, mining influence and the mechanical properties of near-surface surrounding rock are the main factors restricting the control of roadway surrounding rock. Under the double constraints of high ground stress and soft surrounding rock, the physical properties of the roadway surrounding rock deteriorate and the strength decays. At the same time, the roadway surrounding rock induces crack propagation under the action of deviatoric stress and gradient stress, which causes the roadway surrounding rock to appear phenomena such as plastic zone deterioration, rheology, rupture and other phenomena, resulting in continuous large deformation of the roadway surrounding rock. Specifically, the surrounding rock in the shallow range around the roadway shows non-continuous deformation such as expansion and shear dilation, and the roadway shows continuous deformation mainly in the form of plastic deformation under high stress.

[0004] Under the high ground stress environment, some roadways are severely deformed without being affected by mining. The traditional roadway surrounding rock reinforcement controls the deformation of the roadway by improving the bearing capacity of the near-surface surrounding rock. However, the high ground stress in deep mining exceeds the bearing capacity of the roadway surrounding rock, and then the soft rock roadway appears rheological large deformation. It is worth noting that the anchoring support system is not failed when the roadway is repaired, which indicates that the whole anchoring surrounding rock of the roadway has extrusion deformation, showing the typical characteristics of soft rock rheological large deformation. Under the condition of deep mining, the sum of the bearing capacity of the surrounding rock improved by the traditional reinforcement and the original rock bearing capacity is less than the ground stress, which is the mechanical essence of the large deformation of the surrounding rock.

[0005] The roadway surrounding rock control technology in deep mining mainly includes reinforcement, such as anchor support, anchor cable support, shotcrete support, U-shaped steel support, and single hydraulic prop. The traditional roadway surrounding rock reinforcement technology can effectively enhance the bearing capacity of the surrounding rock under the condition of small ground stress in shallow mining environment, and then realize the control of the roadway surrounding rock. However, the high ground stress in deep mining makes soft rock more prone to plastic deformation and rheological deformation. The control idea of improving the bearing capacity of the near-surface surrounding rock of the roadway by traditional reinforcement measures cannot effectively control the large deformation of the surrounding rock in deep mining. The resistance of the support system often cannot match the deformation of the rock mass under the action of high ground stress, which leads to the intensification of the deformation of the roadway and the failure of the support system.

[0006] Therefore, the traditional roadway surrounding rock reinforcing support technology cannot fundamentally curb the deformation of the roadway surrounding rock under the deep mining condition, thereby leading to high roadway maintenance frequency and cost, and causing serious influence on the mine safety production. It is necessary to jointly control the deformation of the surrounding rock from the aspects of improving the stress environment of the roadway and strengthening the bearing capacity of the surrounding rock, and it is urgent to propose a safe, reliable and effective deep soft rock large roadway surrounding rock control technology. SUMMARY

[0007] In view of the above, in order to overcome the defects of the prior art, the embodiment of the present application provides a roadway surrounding rock fracturing ring construction outer self-bearing ring and near surface yielding support ring collaborative control method, which at least partially solves the above technical problems.

[0008] The technical scheme adopted by the embodiment of the present application is as follows: a roadway surrounding rock fracturing ring construction outer self-bearing ring and near surface yielding support ring collaborative control method, comprising the following steps:

[0009] Exploring the fracturing target rock layer meeting the physical and mechanical parameters around the roadway;

[0010] Determining the characteristic parameters of the surrounding rock loose ring, and then determining the range of the near surface yielding support ring;

[0011] Determining the pulse fracturing borehole length according to the target fracturing rock layer, and obtaining the pulse fracturing weakening ring range;

[0012] Weakening the rock layer outside the yielding support ring by the pulse fracturing mode to form a pulse fracturing weakening ring, so as to achieve the purpose of energy absorption, and at the same time, transferring the high support stress of the surrounding rock in the pulse fracturing weakening ring to the far-field hard rock layer, and constructing the far-field surrounding rock outer self-bearing ring;

[0013] Constructing the near surface yielding support ring by the active and passive yielding support modes, and forming a buffer zone between the yielding support ring and the pulse fracturing weakening ring.

[0014] Further, the roof, sidewall and floor of the surrounding rock near the roadway are provided with exploration holes, the surrounding rock lithology near the roadway is determined, and the physical and mechanical parameters thereof are tested in the laboratory; the rock layer with high strength, good integrity, large stiffness and large thickness is determined as the key rock layer, which is used as the subsequent pulse fracturing target rock layer.

[0015] Further, the characteristic parameters of the surrounding rock loose ring include the loose ring radius, the loose ring thickness, the maximum loose stress, the stress distribution in the loose ring and the plastic zone range of the surrounding rock in the loose ring;

[0016] The range of the near surface yielding support ring is greater than the range of the surrounding rock loose ring by 5m to 10m.

[0017] Further, the number of drill holes is calculated according to the radial main crack extension range of a single drill hole of 15m.

[0018] A buffer distance of 15m-30m is provided between the pulse fracturing weakening ring and the near-surface pressure relief support ring.

[0019] Furthermore, the pulse weakening configuration is as follows: when the target rock layer is a single layer and the thickness is ≤10m, a radial pulse hydraulic fracturing network is formed by sequentially performing pulse hydraulic fracturing on each borehole, wherein the pulse fracturing parameters are: pulse frequency 5Hz~10Hz, displacement 80L / min~120L / min, and pulse waveform sine wave.

[0020] When the target rock stratum has multiple layers or a single layer thickness >10m, the retreating segmented pulse fracturing method is used to perform multiple pulse fracturing operations on each borehole in the same thick and hard rock stratum. The retreating distance of the retreating segmented pulse fracturing method is 5m to 10m.

[0021] Furthermore, for fracturing operations in soft rocks such as mudstone that soften upon contact with water, the amount of water used for fracturing is controlled, the total fluid volume is read in real time throughout the fracturing process, and fracturing is stopped immediately when the test threshold is reached; the fracturing backflow water is discharged to a designated drainage ditch through a dedicated drainage pipeline.

[0022] Furthermore, the construction of the near-surface pressure support ring includes,

[0023] Initial pressure relief support: The surrounding rock near the surface of the roadway is supported by pressure relief anchor bolts, and then anchor mesh is laid on the roof and both sides and shotcrete is sprayed in sequence;

[0024] Secondary support: The roadway is reinforced with anchor cables, forming a coupled anchoring structure together with the primary support system. A retractable U-shaped steel arch frame with reserved deformation capacity is laid across the entire cross section of the roadway and shotcrete is applied.

[0025] Furthermore, in roadways prone to floor heave, the construction of near-surface pressure-relief support rings also includes the construction of a composite inverted arch structure: the tensile stress of the floor slab is converted into circumferential compressive stress through the arc-shaped inverted arch structure, and the fissures in the surrounding rock of the floor slab are filled with a graded grouting process to form a "flexible buffer-rigid bearing" composite structure.

[0026] Furthermore, the ultimate tensile strength σ of the anchor bolt... u The surrounding rock rheological rate is dynamically matched with the elongation δ, and adapted in stages according to the geostress gradient, i.e., σ u With δ and ground stress σ v Compressive strength σ of the surrounding rock near the surface c The ratio σ v / σ c Increase as it rises.

[0027] Furthermore, the allowable deformation amount of the retractable U-shaped steel arch frame is determined according to the following method:

[0028] First, the extent of the weakened zone was determined by cross-validation of borehole inspection and numerical simulation after fracturing, thus obtaining the radius R of the weakened zone in pulse fracturing. f ;

[0029] Secondly, in-situ core sampling was performed to test the elastic modulus E0 of the surrounding rock before fracturing of the pulse-fracturing weakened zone, the elastic modulus E1 of the surrounding rock after fracturing of the pulse-fracturing weakened zone, and the initial in-situ stress σ of the near-surface pressure relief support ring. v0 ,pass:

[0030]

[0031] The reduction factor η of the weakening modulus of the surrounding rock was calculated, and based on the above calculation results, the following was applied:

[0032]

[0033] The effective stress σ transmitted to the near-surface pressure support ring is calculated. v1 In the formula, D is the distance from the outer edge of the pulse fracturing weakening zone to the roadway side;

[0034] Then effectively stress σ v1 The surrounding rock strength σ of the near-surface pressure support ring c The ratio H is obtained through:

[0035]

[0036] The calculation is then performed, and the reserved deformation amount U of the retractable U-shaped steel arch frame is set according to the H-level.

[0037] The beneficial effects achieved by the present invention using the above structure are as follows:

[0038] (1) This invention actively regulates the stress field of the surrounding rock through pulse fracturing weakening technology, transfers the high bearing stress of the near-surface surrounding rock to the deep hard rock layer in the far field, and constructs a self-bearing ring of the far-field surrounding rock; then, by utilizing the "outer self-bearing ring-near-surface pressure relief support ring" collaborative control system, the outer ring achieves rock layer self-bearing by relying on stress redistribution, and the inner ring works in synergy with pressure relief support methods such as prestressed pressure relief anchors, laying buffer layers and retractable U-shaped steel arches to generate controllable deformation in the near-surface surrounding rock, achieve local pressure relief, and optimize the compatibility between the support system and the deformation of the surrounding rock;

[0039] (2) This invention addresses the problem of large deformation of surrounding rock caused by the ternary contradiction of "high ground stress - weak bearing capacity of surrounding rock - rigid support system" in deep soft rock tunnels. By coupling stress environment optimization and reconstruction of the mechanical relationship between surrounding rock and support, with stress environment optimization and deformation coordination control as the core, it breaks through the adaptability bottleneck of traditional rigid support system under the dual constraints of high ground stress and weak bearing capacity of soft rock.

[0040] (3) The application significantly enhances the self-stability of surrounding rock and the dynamic response characteristics of the supporting system by establishing a "outer self-bearing-inner pressure relief regulation" synergistic mechanism, realizes the integrated goal of rheological inhibition, controllable deformation and instability risk gradient prevention and control, and provides a reference for deep soft rock roadway surrounding rock control. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 is a step flow chart of a surrounding rock pressure cracking ring construction outer self-bearing ring and near surface pressure relief support ring synergistic control method;

[0042] Figure 2 is a surrounding rock pressure cracking ring construction outer self-bearing ring and near surface pressure relief support ring synergistic control method schematic diagram for a single soft rock roadway in a deep well;

[0043] Figure 3 is a surrounding rock pressure cracking ring construction outer self-bearing ring and near surface pressure relief support ring synergistic control method schematic diagram cross-sectional view for multiple system roadways at the same mining level;

[0044] Figure 4 is a surrounding rock pressure cracking ring construction outer self-bearing ring and near surface pressure relief support ring synergistic control method schematic diagram plan view for multiple system roadways at the same mining level;

[0045] In the drawings:

[0046] 1-soft weak rock stratum with lower bearing capacity, 2-hard rock stratum with stronger bearing capacity, 3-soft rock roadway, 4-near surface pressure relief support ring, 5-pulse pressure cracking weakening ring, 6-pulse pressure cracking fracture network, 7-pulse pressure cracking borehole, 8-pressure relief anchor rod, 9-concrete shotcrete layer, 10-reserved deformation of retractable U-shaped steel arch, 11-original cross section of roadway, 12-anchored grouting rod, 13-retractable U-shaped steel arch, 14-buffer zone, 15-distant field surrounding rock self-bearing ring, 16-supporting pressure distribution curve;

[0047] 1-1-soft weak rock stratum where the protected roadway is located, 1-2-mining stratum, 3-1-return air roadway, 3-2-railway roadway, 3-3-gob transportation roadway, 3-4-belt conveyor transportation roadway, 3-5-working face track roadway, 3-6-working face transportation roadway, 3-7-working face, 3-8-gob, 5-1-middle point of the line connecting the two farthest points in the protected roadway, 5-2-long axis length of the pulse pressure cracking weakening ring, 5-3-short axis length of the pulse pressure cracking weakening ring, 16-1-supporting pressure rising area of the near surface surrounding rock pressure relief support ring, 16-2-supporting pressure reducing area of the near surface surrounding rock pressure relief support ring, 16-3-supporting pressure rising area of the buffer zone, 16-4-supporting pressure reducing area of the pulse pressure cracking weakening ring, 16-5-supporting pressure rising area of the distant field surrounding rock self-bearing ring, 16-6-supporting pressure reducing area of the distant field surrounding rock self-bearing ring, 16-7-distant field surrounding rock original rock stress area.

[0048] The accompanying drawings are included to provide a further understanding of embodiments of the application, and are incorporated in and constitute a part of the specification, illustrate embodiments of the application, and explain the application without limiting the application to the illustrations. DETAILED DESCRIPTION

[0049] The technical solutions in the embodiments of the application will be clearly and completely described in connection with the drawings in the embodiments of the application. Obviously, the described embodiments are only a part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments of the application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the application.

[0050] In the description of the embodiments of the application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the embodiments of the application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the application.

[0051] The technical problem to be solved by the application is how to control the deformation of soft rock roadway 3 in a high-stress environment, transfer the support stress of the roadway surrounding rock, and ensure the long-term service of the deep soft rock roadway 3.

[0052] Under deep mining conditions, the sum of the bearing capacity of the traditional reinforced support and the bearing capacity of the original rock is less than the ground stress, resulting in large deformation phenomena such as rheology and structural instability of the roadway surrounding rock. The traditional roadway surrounding rock reinforcement technology cannot fundamentally curb the deformation of the roadway surrounding rock under deep mining conditions, thereby leading to high frequency of roadway maintenance and high cost, and causing serious impact on mine safety production, so the soft rock roadway 3 control problem under high ground stress environment is faced.

[0053] As shown in Figure 1 To solve the above problems, the application provides a roadway surrounding rock fracturing ring construction outer self-bearing ring and near-surface yielding support ring collaborative control method, comprising the following steps:

[0054] S1, survey the roadway lithology to determine the key rock stratum: construction of roof-to-floor exploration holes in the roof, sidewall and floor of the surrounding rock near the protected roadway, determine the lithology of the roadway near-surface surrounding rock, and test its physical and mechanical parameters in the laboratory; determine the rock stratum with high strength, good integrity, large stiffness and large thickness as the key rock stratum as the subsequent pulse fracturing target rock stratum.

[0055] S2, determining the roadway surrounding rock loose circle: through the acoustic wave detection technology, borehole peep and geological radar, the characteristic parameter experience value of the surrounding rock loose circle is obtained, including the loose circle radius, the loose circle thickness, the maximum loose stress, the stress distribution in the loose circle and the surrounding rock plastic zone range in the loose circle, which provides the basis for determining the near surface yielding support circle 4 range.

[0056] S3, determining the pulse fracturing weakening circle 5 range: according to the target fracturing rock layer of the roadway near surface surrounding rock, the length of the pulse fracturing borehole 7 (i.e. borehole) is determined, and then the pulse fracturing weakening circle 5 diameter is obtained, the number of pulse fracturing boreholes 7 is calculated according to the radial main crack extension range of a single pulse fracturing borehole 7, and the pulse fracturing weakening circle 5 forms a whole circle with the roadway as the center; the pulse fracturing weakening circle 5 and the near surface yielding support circle 4 form a certain buffer distance to prevent the pulse fracturing crack from expanding to the support area to cause the support system to fail, and the preferred buffer distance is 15m-30m; for the development roadway or the soft rock roadway 3 with a straight line distance less than 50m and parallel axes, the pulse fracturing weakening circle 5 is in the shape of an ellipse, the center of which is the midpoint of the line connecting the farthest ones in the protected roadways, and the length of the major axis is the sum of the line connecting the farthest ones in the protected roadways, the radius of the near surface yielding support circle 4 of a single roadway, and the buffer distance between the near surface yielding support circle 4 and the pulse fracturing weakening circle 5; the vertical range of the pulse fracturing weakening circle 5 cannot exceed the coal seam or the adjacent coal seam to be mined.

[0057] The soft rock roadway 3 includes a return air roadway 3-1, a track roadway 3-2, a gangue transportation roadway 3-3, a belt conveyor transportation roadway 3-4, a working face track roadway 3-5, a working face transportation roadway 3-6, a working face 3-7, and a goaf 3-8.

[0058] S4, determining the near surface yielding support circle 4 range: the near surface yielding support circle 4 range is greater than the roadway surrounding rock loose circle range determined in step S2 by 5-10m; for the roadway affected by mining, the surrounding rock loose circle range determined for the roadway is used as the reference; for the roadway not affected by mining, the surrounding rock loose circle experience value of the adjacent working face affected by mining or the roadway with similar conditions is used as the calculation basis.

[0059] S5, constructing the pulse fracturing weakening circle 5 of the outer surrounding rock layer: the rock layer outside the pulse fracturing near surface bearing circle is weakened by pulse fracturing, and a certain range of weak structure is formed by the pulse fracturing crack network 6, which can absorb the high dynamic load of the initial mining and periodic breaking of the roof, and at the same time, the high support stress of the near surface yielding support circle 4 is transferred to the "far field surrounding rock self-bearing circle 15", the bearing capacity of the far field hard rock layer is utilized, the advantage of higher strength of the far field surrounding rock under the triaxial stress state is utilized, and the stress environment of the roadway near surface surrounding rock is optimized.

[0060] S51, drilling and pulse fracturing: construction of fracturing drillings in the roof, sidewall and floor of the roadway, and pulse hydraulic fracturing is carried out in each drilling in turn, a radial pulse fracture network 6 is formed to absorb the elastic energy released by the roof breakage, and at the same time, the near-surface rock support stress in the pulse fracturing weakened circle 5 is transferred to the far-field hard surrounding rock outside the weakened circle to build an outer self-bearing circle of the far-field surrounding rock, and the high self-bearing capacity of the far-field surrounding rock is used as the main way to resist the ground stress, so as to realize the stress environment optimization of the soft rock roadway 3.

[0061] S52: drilling hole sealing: grouting and sealing of the pulse fracturing drilling 7 to prevent the closure of the pulse fracturing drilling 7 under the action of the ground stress, so that the pulse fracturing liquid is discharged to the soft rock layer which expands and softens when it comes into contact with water, thereby reducing the strength and normal stress of the near-surface soft surrounding rock, and causing the surrounding rock loose circle to expand again.

[0062] S6, construction of a near-surface yielding support circle 4 of the whole section of the roadway: a near-surface yielding support circle 4 is constructed by active and passive yielding support methods to adapt to the plastic deformation of the surrounding rock and at the same time to strengthen the bearing capacity of the near-surface surrounding rock.

[0063] S61, primary yielding support of anchor net and shotcrete: high-strength, high-toughness and high-prestress yielding anchor 8 is used to support the near-surface surrounding rock of the roadway, and then anchor net is laid on the roof and shotcrete is sprayed on the roof and sidewall.

[0064] S62, secondary support of shrinkable U-shaped steel arch 13 and prestressed anchor cable: after the first deformation of the surrounding rock tends to be stable, the secondary support of the surrounding rock is carried out to provide the final support strength and stiffness for the roadway. High-prestress anchor cable is used to strengthen the support of the roadway, which forms a coupled anchoring structure with the primary support system in step S61 to improve the effect of the strengthened support; secondly, the shrinkable U-shaped steel arch 13 with a reserved deformation amount is laid on the whole section of the roadway and shotcrete is sprayed.

[0065] S63, construction of flexible buffer-rigid bearing type composite counter-arch structure: for the roadway prone to floor heave, the radial tensile stress of the floor is converted into circumferential compressive stress through the arc-shaped counter-arch structure, and the hierarchical grouting process is used to fill the fractures of the floor surrounding rock to form a "flexible buffer-rigid bearing" composite structure to inhibit the amount of floor heave. First, low-pressure grouting is used to fill large-scale fractures to form a low-modulus flexible buffer zone to absorb the deformation energy generated by the floor heave through plastic deformation; secondly, high-pressure grouting is used to split and penetrate the micro-fractures of the floor to form a high-modulus rigid bearing zone, and the concrete as a whole forms a concrete shotcrete layer 9.

[0066] In a further embodiment of the present embodiment, in step S2, for the roadway not affected by mining, the determination of the empirical value of the characteristic parameter of the surrounding rock loose circle in step S2 is carried out in different working face roadways of the same mining area in the mine which have been affected by mining.

[0067] In a further implementation form of the present embodiment, in step S2, the ground penetrating radar is preferably a non-destructive testing technique for the roadway loose circle, and the accurate surrounding rock loose circle range is obtained through mutual comparison and verification of different detection techniques, thereby providing a basis for subsequent determination of the yield support circle range.

[0068] In a further implementation form of the present embodiment, in step S51, if the key stratum determined in step S1 has multiple layers or a single layer with a large thickness (greater than 10 m), a retreating segmented pulse fracturing technique is used, and multiple pulse fracturing is performed in the same thick hard stratum to strengthen the weakening effect on the high-integrity thick hard stratum. The preferred retreating distance is 5-10 m.

[0069] In a further implementation form of the present embodiment, in step S51, the preferred parameters of pulse fracturing are: pulse frequency 5-10 Hz, displacement 80-120 L / min, and pulse waveform sinusoidal wave.

[0070] In a further implementation form of the present embodiment, in step S51, for the soft rock arranged in mudstone and the like with water-softening characteristics, the following measures are taken to control the water seepage problem between the borehole and the roof: strictly controlling the water amount for fracturing, reading the total liquid amount in real time during the whole fracturing process, and stopping fracturing as soon as the test threshold is reached; and guiding and discharging the fracturing return water to the designated drainage ditch through a special drainage pipeline to avoid direct discharge into the roadway to cause short-term local water accumulation and eliminate the disturbance to production activities.

[0071] In a further implementation form of the present embodiment, in step S51, the outer boundary of the outer self-bearing circle of the far-field surrounding rock is taken as 5% higher than the original rock stress as the demarcation.

[0072] In a further implementation form of the present embodiment, in step S61, if the roadway has been deformed due to the influence of dynamic pressure and static pressure, first, the side and bottom of the roadway are expanded to restore the net cross-sectional size of the roadway after support to the original design cross-sectional size.

[0073] In a further implementation form of the present embodiment, in step S61, the high-strength, high-toughness and high-prestress yield pressure anchor rod 8 adopts a constant resistance anchor rod, which can provide constant resistance and significant plastic slip energy absorption when the surrounding rock deforms, thereby avoiding failure of the support system due to excessive deformation.

[0074] In a further implementation form of the present embodiment, in step S61, when the shotcrete yield pressure layer is sprayed, a certain thickness of concrete is first sprayed, a buffer layer is laid outside the concrete layer, which is used to attenuate stress waves and absorb energy, and another layer of concrete is sprayed outside the buffer layer. Preferably, the buffer layer material is closed-cell aluminum foam.

[0075] In a further embodiment of this example, in steps S61 and S62, the high-strength, high-toughness, high-prestressed relief anchor rod 8 and the anchor cable are made of high-toughness alloy materials. The initial prestress is applied in stages according to the ground stress gradient. The anchor rod can be reduced based on the expansion range of the plastic zone of the surrounding rock. When the load reaches the preset relief threshold, it triggers slippage energy dissipation to avoid stress concentration leading to brittle failure.

[0076] In a further embodiment of this example, in steps S61 and S62, the ultimate tensile strength σ of the high-strength, high-toughness, high-prestressed anchor bolt 8 is... u The surrounding rock rheological rate is dynamically matched with the elongation δ, and adapted in stages according to the geostress gradient, i.e., σ u With δ and ground stress σ v Compressive strength σ of the surrounding rock near the surface c The ratio σ v / σ c Increased by rising; high strength, high toughness, and high prestress cause the elongation δ of the anchor bolt 8 to increase with its ultimate tensile strength σ. u Dynamic equilibrium is achieved based on an inverse proportional function relationship.

[0077] In a further embodiment of this example, in step S62, the reserved deformation amount 10 of the retractable U-shaped steel arch frame is determined by the following method:

[0078] First, the extent of the weakened zone is determined by borehole inspection after fracturing, and the radius R of the weakened zone from the pulse fracturing is obtained. f ;

[0079] Secondly, in-situ core sampling was performed to test the elastic modulus E0 of the surrounding rock before fracturing of the pulse-fracturing weakened zone, the elastic modulus E1 of the surrounding rock after fracturing of the pulse-fracturing weakened zone, and the initial in-situ stress σ of the near-surface pressure relief support ring. v0 ,pass:

[0080]

[0081] The reduction factor η of the weakening modulus of the surrounding rock was calculated, and based on the above calculation results, the following was applied:

[0082]

[0083] The effective stress σ transmitted to the near-surface pressure support ring is calculated. v1 In the formula, D is the distance from the outer edge of the pulse fracturing weakening zone to the roadway side;

[0084] Then effectively stress σ v1 The surrounding rock strength σ of the near-surface pressure support ring c The ratio H is obtained through:

[0085]

[0086] The reserved deformation U of the telescopic U-shaped steel arch is calculated, and then the reserved deformation U is set according to the H classification, and if the deformation rate exceeds the threshold value, the reserved deformation is adaptively adjusted according to the stress release requirement.

[0087] Embodiment 1

[0088] As shown in Figure 2 For the surrounding rock control of the deep well single soft rock roadway 3, the application provides a roadway surrounding rock fracturing ring construction outer self-bearing ring and near surface yielding support ring cooperative control method, and the specific implementation steps are as follows:

[0089] Step S1, surveying the roadway lithology to determine the key rock stratum: for the to-be-protected roadway 3, the excavation is in the soft rock stratum 1 (that is, the soft rock stratum 1-1 where the to-be-protected roadway is located) with lower bearing capacity, and above and below which may be the hard rock stratum 2 with higher bearing capacity, roof and floor exploration holes are constructed in the roof, sidewall and floor of the surrounding rock near the to-be-protected roadway to determine the lithology of the surrounding rock near the to-be-protected roadway, and the physical and mechanical parameters thereof are tested in the laboratory; the rock stratum with high strength, good integrity, large stiffness and large thickness is determined as the key rock stratum as the subsequent pulse fracturing target rock stratum.

[0090] Step S2, measuring the roadway surrounding rock loose ring: through the acoustic wave detection technology, borehole peeping and geological radar, the characteristic parameter empirical value of the surrounding rock loose ring is obtained, including the loose ring radius, the loose ring thickness, the maximum loose stress, the stress distribution in the loose ring and the plastic zone range of the surrounding rock in the loose ring, which provides a basis for determining the range of the near surface yielding support ring 4. For the roadway not affected by mining, the measurement of the characteristic parameter empirical value of the surrounding rock loose ring is carried out in the different working face roadways of the same mining area in the mine which have been affected by mining.

[0091] The geological radar is the preferred nondestructive testing technical means for the roadway loose ring, and through the mutual comparison and verification of different detection technologies, the accurate range of the surrounding rock loose ring is obtained, which provides a basis for determining the range of the subsequent yielding support ring.

[0092] Step S3, determining the range of the pulse fracturing weakened ring 5: according to the target fracturing rock stratum of the surrounding rock near the roadway, the length of the pulse fracturing borehole 7 is determined, and then the diameter of the pulse fracturing weakened ring 5 is obtained, the number of the pulse fracturing borehole 7 is calculated according to the radial main crack extension range of a single pulse fracturing borehole 7, and the pulse fracturing weakened ring 5 forms a complete circle with the roadway as the center; the pulse fracturing weakened ring and the near surface yielding support ring form a buffer zone 14 to prevent the pulse fracturing crack from expanding to the support area to cause the failure of the support system, and the preferred length of the buffer zone 14 is 15m-30m.

[0093] Step S4, determining the range of the near-surface yielding support ring 4: the range of the near-surface yielding support ring 4 is greater than the range of the roadway surrounding rock loose ring determined in step S2 by 5-10 m; for the roadway affected by mining, the range of the surrounding rock loose ring determined in the roadway is used as the reference; for the roadway not affected by mining, the surrounding rock loose ring experience value of the roadway adjacent to the working face affected by mining or the roadway with similar conditions is used as the calculation basis.

[0094] Step S5, constructing the pulse fracturing weakened ring 5 of the outer surrounding rock: the pulse fracturing weakened ring 5 of the outer surrounding rock of the near-surface bearing ring is fractured, a certain range of weak structure is formed by generating the pulse fracture network 6, on the one hand, the high dynamic load of the initial mining and periodic breaking of the roof is absorbed, and at the same time, the high support stress of the near-surface yielding support ring 4 is transferred to the far-field self-bearing ring 15 of the surrounding rock, the bearing capacity of the far-field hard rock is utilized, the surrounding rock stress environment near the roadway is optimized.

[0095] Step S51, drilling and pulse fracturing: the fracturing drilling holes 7 are constructed in the roof, sidewall and floor of the roadway, and the pulse hydraulic fracturing is carried out for each drilling hole in turn, the radial pulse fracture network 6 is formed, the elastic energy released by the roof breaking is absorbed, and at the same time, the near-surface surrounding rock support stress in the pulse fracturing weakened ring 5 is transferred to the far-field hard surrounding rock outside the weakened ring, so as to construct the far-field surrounding rock outer self-bearing ring 15, utilize the high self-bearing capacity of the far-field surrounding rock as the main way to resist the ground stress, and realize the stress environment optimization of the soft rock roadway 3.

[0096] If the key rock layer determined in step S1 has multiple layers or a single layer with a large thickness (greater than 10 m), the step-back segmented pulse fracturing technology is used, the pulse fracturing is carried out multiple times in the same thick hard rock layer, the weakening effect on the high integrity thick hard rock layer is strengthened, and the preferred step-back distance is 5-10 m.

[0097] The preferred parameters of the pulse fracturing are: pulse frequency 5-10 Hz, displacement 80-120 L / min, and pulse waveform sinusoidal wave.

[0098] For the soft rock arranged in mudstone and the like with water-softening characteristics, the following measures are taken to control the water seepage problem of the drilling hole 7 and the roof: the fracturing water amount is strictly controlled, the total liquid amount is read in real time during the whole fracturing process, and the fracturing is stopped immediately when the test threshold value is reached; the fracturing return water is guided and discharged to the designated drainage ditch through a special drainage pipeline, so as to avoid direct discharge into the roadway to cause short-term local water accumulation and eliminate the disturbance to production activities.

[0099] The outer boundary of the far-field surrounding rock outer self-bearing ring 15 is taken as 5% higher than the original rock stress as the demarcation.

[0100] Step S52: Drilling hole sealing: grouting sealing is performed on the pulse fracturing drilling hole 7 to prevent the fracturing cracks from closing under the action of ground stress, causing the fracturing fluid to be backflowed to the soft rock layer that expands and softens in water, thereby reducing the strength and normal stress of the near-surface soft surrounding rock fracture surface, leading to the expansion of the surrounding rock relaxation zone again.

[0101] Step S6, constructing a roadway full-section near-surface yielding support ring 4: a near-surface yielding support ring 4 is constructed through active and passive yielding support methods to adapt to the stable plastic deformation of the surrounding rock while strengthening the near-surface surrounding rock bearing capacity.

[0102] Step S61, anchor net spray initial yielding support: high-strength, high-toughness, and high-prestress yielding anchor rods 8 are used to support the near-surface surrounding rock of the roadway, and then anchor nets are laid on the roof and concrete 9 is sprayed on the roof and sidewall. If the roadway has been deformed due to dynamic and static pressure, first, the sidewall is expanded and the floor is laid to restore the net cross-sectional size of the supported roadway to the original design cross-sectional size 11.

[0103] When the concrete yielding layer 9 is sprayed, a certain thickness of concrete is first sprayed, a buffer layer is laid on the outside of the concrete layer for stress wave attenuation and energy absorption, and another layer of concrete is sprayed outside the buffer layer. The preferred buffer layer material is closed-cell aluminum foam.

[0104] The high-strength, high-toughness, and high-prestress yielding anchor rods 8 and anchor cables use strong and tough alloy materials, the initial prestress is applied in stages according to the ground stress gradient, the yielding amount of the yielding anchor rods 8 is designed based on the expansion range of the surrounding rock plastic zone, and the sliding energy consumption is triggered when the load reaches the preset yielding threshold, avoiding brittle failure caused by stress concentration. The high-strength, high-toughness, and high-prestress yielding anchor rods 8 use constant resistance anchor rods that provide constant resistance and significant plastic slip energy absorption as the surrounding rock deforms, avoiding failure of the support system due to excessive deformation.

[0105] The ultimate tensile strength σ u of the high-strength, high-toughness, and high-prestress yielding anchor rods 8 dynamically matches the rheological rate of the surrounding rock and is adapted in stages according to the ground stress gradient, i.e., σ u increases with the ratio σ v of the near-surface surrounding rock compressive strength σ c . v The ultimate tensile strength σ c of the high-strength, high-toughness, and high-prestress yielding anchor rods 8 and the elongation δ of the high-strength, high-toughness, and high-prestress yielding anchor rods 8 are inversely proportional to the ratio σ u .

[0106] Step S62, collapsible U-shaped steel arch 13 cooperates with prestressed anchor cable secondary support: after the primary deformation of the surrounding rock tends to be stable, the secondary support of the surrounding rock is carried out to provide the final support strength and stiffness for the roadway. High prestressed anchor cable is used to strengthen the support of the roadway, which forms a coupled anchoring structure with the primary support system in step S61, and improves the strengthening support effect; secondly, the collapsible U-shaped steel arch 13 with reserved deformation is laid on the whole section of the roadway and the concrete 9 is sprayed.

[0107] The reserved deformation amount 10 of the collapsible U-shaped steel arch is determined by the following method:

[0108] Firstly, the range of the pulse pressure weakening zone is determined by drilling and peering after fracturing to obtain the pulse pressure weakening ring radius R f ;

[0109] Secondly, the in-situ core drilling is carried out, and the elastic modulus E0 of the surrounding rock in the pulse pressure weakening ring before pressure cracking, the elastic modulus E1 of the surrounding rock in the pulse pressure weakening ring after pressure cracking and the initial ground stress σ v0 of the near surface yielding support ring are respectively tested in the laboratory, by:

[0110]

[0111] The surrounding rock weakening modulus reduction coefficient η is calculated, and based on the above calculation results, the effective ground stress σ v1 transferred to the near surface yielding support ring is calculated by:

[0112]

[0113] , wherein D is the distance from the outer edge of the pulse pressure weakening ring to the roadway side;

[0114] Then the ratio H of the effective ground stress σ v1 to the surrounding rock strength σ c of the near surface yielding support ring is calculated by:

[0115]

[0116] , and then the reserved deformation amount U of the collapsible U-shaped steel arch is set according to the H grading, and if the deformation rate exceeds the threshold value, the reserved deformation amount is adaptively adjusted according to the stress release requirement.

[0117] Step S63, constructing a flexible buffer-rigid bearing type composite inverted arch structure: for the roadway prone to floor heave, a warp-weft net welded by steel bars is laid, self-drilling hollow grouting anchor rods 12 are drilled and grouted on the floor, the floor tensile stress is converted into ring compressive stress through the arc-shaped inverted arch structure, and the floor surrounding rock fissures are filled by using a staged grouting process to form a "flexible buffer-rigid bearing" composite structure to inhibit the floor heave. First, low-pressure grouting is performed to fill large-scale fissures to form a low-modulus flexible buffer zone to absorb the deformation energy generated by floor heave through plastic deformation; and then high-pressure grouting is performed to split and penetrate the micro-fissures of the floor to form a high-modulus rigid bearing zone.

[0118] Through the above-mentioned roadway surrounding rock fracturing ring construction outer self-bearing ring and near surface pressure relief supporting ring collaborative control method, the stress of the roadway surrounding rock is transferred, and the supporting pressure distribution curve 16 experiences, in sequence from the near surface to the far field: the near surface surrounding rock pressure relief supporting ring supporting pressure rising area 16-1, the near surface surrounding rock pressure relief supporting ring supporting pressure falling area 16-2, the buffer zone supporting pressure rising area 16-3, the pulse fracturing weakened ring supporting pressure falling area 16-4, the far field surrounding rock self-bearing ring supporting pressure rising area 16-5, the far field surrounding rock self-bearing ring supporting pressure falling area 16-6, and the far field surrounding rock original rock stress area 16-7.

[0119] Example 2

[0120] As shown in Figure 3 and Figure 4 , for the surrounding rock control of multiple soft rock system roadways at the same mining level, the near surface pressure relief supporting ring and the supporting pressure curve of a single roadway refer to Figure 2 The present application provides a roadway surrounding rock fracturing ring construction outer self-bearing ring and near surface pressure relief supporting ring collaborative control method, and the specific implementation steps are as follows:

[0121] Step S1, surveying the roadway lithology to determine the key rock stratum: for the to-be-protected roadway 3, which is excavated in a soft rock stratum 1 with low bearing capacity, there may be hard rock strata 2 with high bearing capacity above and below it. Top and floor exploration holes are drilled in the roof, sidewall and floor of the surrounding rock near the to-be-protected roadway to determine the lithology of the near surface surrounding rock, and the physical and mechanical parameters thereof are tested indoors. The rock stratum with high strength, good integrity, large stiffness and large thickness is determined as the key rock stratum, which is used as the target rock stratum for subsequent pulse fracturing.

[0122] Step S2, measuring the roadway surrounding rock loose ring: the characteristic parameter empirical values of the surrounding rock loose ring, including the loose ring radius, the loose ring thickness, the maximum loose stress, the stress distribution in the loose ring and the range of the plastic zone in the surrounding rock in the loose ring, are obtained by using acoustic wave detection technology, borehole peeping and geological radar, which provide a basis for determining the range of the near surface pressure relief supporting ring 4.

[0123] For the roadway not affected by mining, the determination of the empirical value of the characteristic parameters of the surrounding rock loose circle is carried out in the same mining area of the mine.

[0124] The geological radar is a preferred nondestructive testing technique for the roadway loose circle, and through mutual comparison and verification of different detection techniques, the accurate surrounding rock loose circle range is obtained, thereby providing a basis for determining the subsequent yielding support circle range.

[0125] Step S3, determining the range of the pulse fracturing weakened circle 5: the length of the pulse fracturing borehole 7 is determined according to the target fracturing rock stratum of the near-surface surrounding rock of the roadway, and then the diameter of the pulse fracturing weakened circle 5 is obtained, the number of the pulse fracturing borehole 7 is calculated according to the radial main crack extension range of a single pulse fracturing borehole 7, and the pulse fracturing weakened circle 5 forms a complete circle with the roadway as the center; the pulse fracturing weakened circle and the near-surface yielding support circle form a buffer zone 14 to prevent the pulse fracturing cracks from extending to the support area to cause the failure of the support system, and the length of the preferred buffer zone 14 is 15m-30m; for the development roadway or the soft rock roadway 3 with a straight-line distance less than 50m and parallel axes, the pulse fracturing weakened circle 5 is in an elliptical shape, the center of which is the midpoint 5-1 of the connecting line of the return air roadway 3-1 and the belt conveyor transport roadway 3-4 which are the farthest from each other in the protected roadway, and the long axis length 5-2 of the pulse fracturing weakened circle is the sum of the distance between the connecting line of the farthest from each other in the protected roadway and the radius of the near-surface yielding support circle of a single roadway and the distance between the near-surface yielding support circle and the pulse fracturing weakened circle buffer zone 14; the determination of the short axis length 5-3 of the pulse fracturing weakened circle should consider that the vertical fracturing range should not exceed the coal seam or the adjacent coal seam to be mined 1-2.

[0126] Step S4, determining the range of the near-surface yielding support circle 4: the range of the near-surface yielding support circle 4 is greater than the range of the roadway surrounding rock loose circle determined in step S2 by 5-10m; for the roadway affected by mining, the range of the surrounding rock loose circle determined in the roadway is used as the reference; for the roadway not affected by mining, the empirical value of the surrounding rock loose circle of the roadway of the adjacent working face affected by mining or the roadway with similar conditions is used as the calculation basis.

[0127] Step S5, constructing the pulse fracturing weakened circle 5 of the outer surrounding rock stratum: the rock stratum outside the near-surface bearing circle is weakened by pulse fracturing, a certain range of weak structure is formed by the pulse fracturing crack network 6, on the one hand, the high dynamic load of the initial mining and periodic breaking of the roof is absorbed, and on the other hand, the high support stress of the near-surface yielding support circle 4 is transferred to the far-field surrounding rock self-bearing circle 15, the bearing capacity of the far-field hard rock stratum is utilized, the advantage of higher strength of the far-field surrounding rock under the triaxial stress state is utilized, and the stress environment of the near-surface surrounding rock of the roadway is optimized.

[0128] Step S51, drilling and pulse fracturing: construction of fracturing drillings 7 in the roadway roof, sidewall and floor, and then pulse hydraulic fracturing is carried out for each drilling in turn, a radial pulse fracture network 6 is formed to absorb the elastic energy released by the roof breakage, and at the same time, the near-surface surrounding rock support stress in the pulse fracturing weakened circle 5 is transferred to the far-field hard surrounding rock outside the weakened circle, so as to build a far-field surrounding rock outer self-bearing circle 15, and the high self-bearing capacity of the far-field surrounding rock is used as the main way to resist the ground stress, so as to realize the stress environment optimization of the soft rock roadway 3.

[0129] If the key rock layer determined in step S1 has multiple layers or a single layer with a large thickness (greater than 10m), a retreating type segmented pulse fracturing technology is used, and multiple pulse fracturing is carried out in the same thick hard rock layer to strengthen the weakening effect on the high integrity thick hard rock layer, and the preferred retreating distance is 5-10m.

[0130] The preferred parameters of pulse fracturing are: pulse frequency 5-10Hz, displacement 80-120L / min, and pulse waveform sinusoidal wave.

[0131] For the soft rock such as mudstone which has the water-softening characteristics, the following measures are taken to control the water seepage problem of the drillings 7 and the roof: strictly control the fracturing water volume, read the total liquid volume in real time during the whole fracturing process, and stop fracturing immediately when the test threshold is reached; the fracturing return water is guided and discharged to the designated drainage ditch through a special drainage pipeline to avoid direct discharge into the roadway to cause short-term local water accumulation and eliminate the disturbance to production activities.

[0132] The outer boundary of the far-field surrounding rock outer self-bearing circle 15 is taken as the boundary of 5% higher than the original rock stress.

[0133] Step S52: drilling hole sealing: grouting and sealing of the pulse fracturing drillings 7 to prevent the closure of the fracturing fractures under the action of the ground stress, so that the fracturing fluid is backflowed to the soft and weak rock layer which swells and softens when encountering water, and then the near-surface soft and weak surrounding rock breakage strength and normal stress are reduced, resulting in the expansion of the surrounding rock loose circle again.

[0134] Step S6, building a near-surface yielding support circle 4 of the roadway full section: a near-surface yielding support circle 4 is built through active and passive yielding support methods to adapt to the plastic deformation of the surrounding rock and at the same time to strengthen the bearing capacity of the near-surface surrounding rock.

[0135] Step S61, primary yielding support of anchor net and spray: high-strength, high-toughness and high-prestress yielding anchor rods 8 are used to support the near-surface surrounding rock of the roadway, and then anchor nets are laid on the roof and concrete 9 is sprayed on the roof and sidewall. If the roadway has been deformed due to dynamic and static pressure, first, the sidewall is expanded and the floor is laid to restore the net section size of the roadway after support to the original design section size 11.

[0136] When applying the shotcrete compaction layer 9, a certain thickness of concrete is first sprayed. A buffer layer is then laid on the outside of this concrete layer to attenuate stress waves and absorb energy. Another layer of concrete is then sprayed on the outside of the buffer layer. The preferred material for the buffer layer is closed-cell aluminum foam.

[0137] The high-strength, high-toughness, and high-prestressed yielding anchor bolt 8 and anchor cable are made of high-toughness alloy materials. The initial prestress is applied in stages according to the ground stress gradient. The yielding anchor bolt 8 can be designed with a reduction in size based on the expansion range of the plastic zone of the surrounding rock, and triggers slippage energy dissipation when the load reaches the preset yielding threshold, avoiding stress concentration leading to brittle failure. The high-strength, high-toughness, and high-prestressed yielding anchor bolt 8 is a constant-resistance anchor bolt, which provides constant resistance as the surrounding rock deforms and can generate significant plastic slippage energy absorption, preventing the support system from failing due to excessive deformation.

[0138] The high-strength, high-toughness, and high-prestressed anchor bolt 8 has an ultimate tensile strength σ u The surrounding rock rheological rate is dynamically matched with the elongation δ, and adapted in stages according to the geostress gradient, i.e., σ u With δ and ground stress σ v Compressive strength σ of the surrounding rock near the surface c The ratio σ v / σ c Increased by rising; high strength, high toughness, and high prestress cause the elongation δ of the anchor bolt 8 to increase with its ultimate tensile strength σ. u Dynamic equilibrium is achieved based on an inverse proportional function relationship.

[0139] Step S62, Secondary Support with Retractable U-Shaped Steel Arch 13 and Prestressed Anchor Cables: After the primary deformation of the surrounding rock stabilizes, secondary support is carried out to provide the final support strength and stiffness for the roadway. High-prestressed anchor cables are used to reinforce the roadway, forming a coupled anchoring structure together with the primary support system in step S61, thereby improving the reinforcement effect. Secondly, retractable U-shaped steel arch 13 with reserved deformation capacity is laid across the entire cross-section of the roadway and shotcrete 9 is applied.

[0140] The allowable deformation amount 10 for the retractable U-shaped steel arch frame is determined as follows:

[0141] First, the extent of the weakened zone is determined by borehole inspection after fracturing, and the radius R of the weakened zone from the pulse fracturing is obtained. f ;

[0142] Secondly, in-situ core sampling was performed to test the elastic modulus E0 of the surrounding rock before fracturing of the pulse-fracturing weakened zone, the elastic modulus E1 of the surrounding rock after fracturing of the pulse-fracturing weakened zone, and the initial in-situ stress σ of the near-surface pressure relief support ring. v0 ,pass:

[0143]

[0144] The rock weakening modulus reduction coefficient η is calculated, and based on the above calculation results, the effective stress σ

[0145]

[0146] The effective stress σ v1 transferred to the near surface yielding support ring is calculated, where D is the distance from the outer edge of the pulse fracturing weakening ring to the roadway side;

[0147] The ratio H of the effective stress σ v1 to the rock strength σ c of the near surface yielding support ring is calculated by:

[0148]

[0149] The reserved deformation U of the yieldable U-shaped steel arch is calculated according to the H classification, and if the deformation rate exceeds the threshold value, the reserved deformation is adjusted according to the stress release requirement.

[0150] Step S63, constructing a flexible buffer-rigid bearing type composite counter-arch structure: for the roadway prone to floor heave, a warp and weft network formed by welding steel bars is laid, self-drilling hollow grouting anchor rods 12 are drilled and grouted on the floor, the floor tensile stress is converted into ring compressive stress through the arc-shaped counter-arch structure, and the floor surrounding rock fissures are filled by using a staged grouting process to form a "flexible buffer-rigid bearing" composite structure to inhibit the amount of floor heave. First, low-pressure grouting is used to fill large-scale fissures to form a low-modulus flexible buffer zone to absorb the deformation energy generated by floor heave through plastic deformation; second, high-pressure grouting is used to split and penetrate micro-cracks in the floor to form a high-modulus rigid bearing zone.

[0151] Through the above-mentioned roadway surrounding rock fracturing ring construction outer self-bearing ring and near surface yielding support ring collaborative control method, the roadway surrounding rock stress transfer occurs, and the support pressure distribution curve 16 sequentially experiences: the near surface rock yielding support ring support pressure rising area 16-1, the near surface rock yielding support ring support pressure reducing area 16-2, the buffer zone support pressure rising area 16-3, the pulse fracturing weakening ring support pressure reducing area 16-4, the far field rock self-bearing ring 15 support pressure rising area 16-5, the far field rock self-bearing ring support pressure reducing area 16-6, and the far field rock original stress area 16-7.

[0152] Although embodiments of the present application have been shown and described, it will be understood by those having ordinary skill in the art that various changes, modifications, alternatives, and variations can be made thereto without departing from the principles and spirit of the application.

[0153] The above describes the present application and its embodiments, which are not limited, and the drawings only show one of the embodiments of the present application, and the actual structure is not limited thereto. In general, if a person skilled in the art is inspired, without departing from the inventive concept of the embodiments of the present application, without creative design, similar structure and embodiments to the technical solution, which should belong to the protection scope of the present application.

Claims

1. A method for the coordinated control of an outer self-supporting ring and a near-surface pressure-relief support ring in the construction of a fracturing ring for roadway surrounding rock, characterized in that, Includes the following steps: Explore the surrounding rock strata that meet the physical and mechanical parameters for fracturing; set exploration holes in the roof, sidewalls and floor of the surrounding rock near the roadway to determine the lithology of the surrounding rock near the roadway and test its physical and mechanical parameters in the laboratory. The nearby rock strata with high strength, good integrity, high stiffness and large thickness were identified as key rock strata and used as target rock strata for subsequent pulse fracturing; The characteristic parameters of the loosened zone of the surrounding rock are determined, and then the range of the near-surface pressure relief support ring is determined. The characteristic parameters of the loosened zone of the surrounding rock include the radius of the loosened zone, the thickness of the loosened zone, the maximum loosening stress, the stress distribution within the loosened zone, and the range of the plastic zone of the surrounding rock within the loosened zone. The range of the near-surface pressure relief support ring is 5m to 10m larger than the range of the loosened zone of the surrounding rock. The length of the pulse fracturing borehole is determined based on the target rock strata to obtain the range of the pulse fracturing weakened zone; the number of boreholes is calculated based on the radial main fracture extension range of 15 m for a single borehole; a buffer distance of 15m-30m is provided between the pulse fracturing weakened zone and the near-surface pressure relief support zone; By using pulse fracturing, the rock strata outside the support ring are weakened to form a pulse fracturing weakening ring, which achieves the purpose of energy absorption. At the same time, the high bearing stress of the surrounding rock inside the pulse fracturing weakening ring is transferred to the hard rock strata in the far field, thus constructing a self-bearing ring outside the surrounding rock in the far field. A near-surface pressure-yielding support ring is constructed using both active and passive pressure-yielding support methods, forming a buffer zone between the pressure-yielding support ring and the pulse fracturing weakening ring; the construction of the near-surface pressure-yielding support ring includes... Initial pressure relief support: The surrounding rock near the surface of the roadway is supported by pressure relief anchor bolts, and then anchor mesh is laid on the roof and both sides and shotcrete is sprayed in sequence; Secondary support: The roadway is reinforced with anchor cables, forming a coupled anchoring structure together with the primary support system. A retractable U-shaped steel arch frame with reserved deformation capacity is laid across the entire cross section of the roadway and shotcrete is applied.

2. The method for coordinated control of the outer self-bearing ring and the near-surface pressure-relief support ring in the fracturing ring of the surrounding rock of the roadway according to claim 1, characterized in that, The pulse fracturing weakening configuration is as follows: when the target rock layer is a single layer and the thickness is ≤10m, a radial pulse fracturing network is formed by sequentially carrying out pulse hydraulic fracturing on each borehole. The pulse fracturing parameters are: pulse frequency 5Hz~10 Hz, displacement 80 L / min~120 L / min, and pulse waveform sine wave. When the target rock stratum has multiple layers or a single layer thickness >10 m, the retreating segmented pulse fracturing method is used to perform multiple pulse fracturing operations on each borehole in the same thick and hard rock stratum. The retreating distance of the retreating segmented pulse fracturing method is 5 m to 10 m.

3. The method for coordinated control of the outer self-bearing ring and the near-surface pressure-relief support ring in the fracturing ring of the surrounding rock of the roadway according to claim 1, characterized in that, For fracturing operations in soft rocks such as mudstone that soften upon contact with water, the amount of water used for fracturing is controlled, the total fluid volume is read in real time throughout the fracturing process, and fracturing is stopped immediately when the test threshold is reached; the fracturing backflow water is discharged to the designated drainage ditch through a dedicated drainage pipeline.

4. The method for coordinated control of the outer self-bearing ring and the near-surface pressure-relief support ring in the fracturing ring of the surrounding rock of the roadway according to claim 1, characterized in that, In roadways prone to floor heave, the construction of near-surface pressure relief support rings also includes the construction of a composite inverted arch structure: the tensile stress of the floor slab is converted into circumferential compressive stress through the arc-shaped inverted arch structure, and the fissures in the surrounding rock of the floor slab are filled with graded grouting process to form a "flexible buffer-rigid bearing" composite structure.

5. The method for coordinated control of the outer self-bearing ring and the near-surface pressure-relief support ring in the fracturing ring of the surrounding rock of the roadway according to claim 1, characterized in that, The ultimate tensile strength of the anchor bolt With elongation Dynamically match the rheological rate of the surrounding rock and adapt it in stages according to the geostress gradient, that is... and As-situ stress σ v Compressive strength σ of the surrounding rock near the surface c The ratio σ v / σ c Increase as it rises.

6. The method for coordinated control of the outer self-bearing ring and the near-surface pressure-relief support ring in the fracturing ring of the surrounding rock of the roadway according to claim 1, characterized in that, The allowable deformation of the retractable U-shaped steel arch frame is determined by the following method: First, the extent of the weakened zone is determined by borehole inspection after fracturing, thus obtaining the radius of the weakened zone from the pulse fracturing. ; Secondly, in-situ core sampling was performed to test the elastic modulus of the surrounding rock in the pulse fracturing weakened zone before fracturing, using laboratory tests. Elastic modulus of the weakened surrounding rock after pulse fracturing and the initial in-situ stress of the near-surface pressure support ring ,pass: ， The reduction coefficient of the weakening modulus of the surrounding rock was calculated. Based on the above calculation results, the following is adopted: ， The effective stress transmitted to the near-surface pressure support ring was calculated. In the formula, D is the distance from the outer edge of the pulse fracturing weakening zone to the roadway side; Then effective stress The strength of the surrounding rock with the near-surface pressure support ring ratio pass: ， The calculation is then performed, and the reserved deformation amount U of the retractable U-shaped steel arch frame is set according to the H-level.

Images