CN116104502B - Method for reinforcing mountain tunnel crossing coal mine goaf - Google Patents

Abstract

The invention relates to a method for reinforcing a mountain tunnel crossing a goaf of a coal mine. Determining a target tunnel interval to be reinforced along the tunnel; detecting the goaf based on a detection strategy in a preset detection strategy set to obtain parameter information associated with the goaf; determining a reinforcement pile layout scheme for reinforcing the target tunnel section based at least on the parameter information and performing initial grouting based on the reinforcement pile layout scheme; dynamically detecting a goaf crushing range in the drill hole continuously in the initial grouting process to determine whether deviation information associated with the goaf crushing range exists; adjusting the initial grouting scheme when determining that the information which deviates from the breaking range of the adjacent goaf exists; and continuing grouting the goaf based on the adjusted initial grouting scheme. In this way, geological conditions can be revealed in combination with various detection means, and goaf surrounding rock structures can be reinforced and strengthened more efficiently and sufficiently.

Description

Method for reinforcing mountain tunnel crossing coal mine goaf

Technical Field

The present invention relates generally to the field of construction engineering, and in particular to a method for reinforcing mountain tunnels traversing goaf of coal mine.

Background

Along with the development of rail transit and the progress of high-speed railway technology in China, more and more railway tunnels need to pass through poor geology, wherein the condition of passing through a coal mine goaf is not poor. Under the condition, problems such as water gushing and mud bursting, tunnel settlement cracking, gas outburst and the like can occur in the tunnel construction process. In addition, goaf mining or super mining is possible, most goafs are closed and cannot enter a mine for actual measurement, and irreparable engineering accidents can be caused if corresponding measures are not taken in advance.

The existing grouting reinforcement means for the goaf and the overlying stratum thereof are limited by the single monitoring means, insufficient grouting is easy to occur, a good integral structure cannot be formed in an affected area of the goaf, the reinforcement effect is affected, and hidden danger is caused by burying of tunnel engineering. Moreover, current solutions do not fully utilize existing structural configurations during the reinforcement process to dynamically adjust the construction solution to address the particular conditions that occur during the construction process. Therefore, a comprehensive reinforcement technology for more efficiently and fully reinforcing and strengthening surrounding rock structures of the goaf becomes important in the situation that a mountain tunnel passes through the goaf of the coal mine and can be combined with various detection means to reveal geological conditions.

Disclosure of Invention

The object of the present invention is to provide a method for reinforcing mountain tunnels crossing goaf of coal mine, which at least partly solves the problems existing in the prior art.

According to a first aspect of the present invention there is provided a method for reinforcing a mountain tunnel crossing a goaf of a coal mine. The method includes determining a target tunnel section to be consolidated along the tunnel, the target tunnel section at least partially spanning the goaf; detecting the goaf at the bottom of the target tunnel section based on one or more detection strategies in a preset detection strategy set to obtain parameter information associated with the goaf, wherein the parameter information comprises information indicating a breaking range of the goaf adjacent to the goaf; determining a reinforcement pile layout scheme for reinforcing the target tunnel section based on at least the parameter information and performing initial grouting based on the reinforcement pile layout scheme in which a plurality of the reinforcement piles are arranged in a plurality of boreholes and in which at least a part of the reinforcement piles pass through the goaf crushing range; continuing to dynamically detect the goaf crushing scope within the borehole during the initial grouting process to determine whether deviation information associated with the goaf crushing scope exists, wherein the deviation information deviates from information indicative of an adjacent goaf crushing scope; upon determining that there is a deviation from the information indicative of the extent of goaf fragmentation adjacent the goaf, adjusting an initial grouting regime; and continuing grouting the goaf based on the adjusted initial grouting scheme.

In some embodiments, the method further comprises: the target tunnel interval is obtained by excavating by adopting a cross intermediate wall method, and blasting short footage excavation is controlled in the excavating process; and performing advanced support by adopting a pipe shed, and performing primary support on the target tunnel section by adopting a full-ring steel frame.

In some embodiments, the preset detection strategy set at least comprises a transient electromagnetic method, a drilling method, a comprehensive logging method, an in-hole television method, a cross-hole CT method and a sampling test method; and/or the parameter information further comprises a position, depth, range and surrounding rock condition for the goaf; and/or the reinforcing piles comprise one or more of steel flower pipes or sleeve valve steel pipes.

In some embodiments, determining a reinforcement pile layout scheme for reinforcing the target tunnel section based at least on the parameter information and performing preliminary grouting based on the reinforcement pile layout scheme includes: performing a water-pressure test on each of the boreholes prior to the initial grouting to determine a permeability parameter of the formation in which the target tunnel section is located, the permeability parameter comprising one or more of a specific water absorption or a permeability coefficient value; determining one or more of slurry material, slurry concentration or water-to-solid ratio, grouting pressure, grouting speed, and slurry diffusion range based on the permeation parameter; determining the initial grouting scheme based on one or more of the slurry material, the slurry concentration, the grouting pressure, the grouting speed, and the slurry diffusion range; and performing the initial grouting using the initial grouting scheme.

In some embodiments, the performing a water-pressure test on each of the boreholes prior to the initial grouting comprises: before water pressing, observing the water level of a pressure measuring water hole and an adjacent drilling hole; observing water level change of adjacent drilling holes in the water pressing process; and observing the water levels of the pressurized water drilling hole and the adjacent drilling holes and the descending speed of the water levels after the pressurized water drilling hole and the adjacent drilling holes.

In some embodiments, the unit water absorption is derived based on the following equation w=q/LS, wherein: w is the water absorption of the rock stratum unit, Q is the pressing flow, S is the test pressure head, and L is the length of the pressurized water section.

In some embodiments, continuing to grouting the goaf based on the adjusted initial grouting regimen comprises: and when the grouting pressure reaches the design final pressure value and is stable for 10 minutes without grouting, ending the grouting process.

In some embodiments, the method further comprises: and after the grouting process is finished, one or more methods of drilling sampling, a pressurized water test, a transient electromagnetic method and comprehensive logging are utilized to check the grouting effect until the checking result meets the design requirement.

In some embodiments, the method further comprises: and carrying out secondary lining on the goaf after the primary support deformation is stable, wherein the secondary lining adopts a reinforced concrete structure, the reinforced concrete structure is configured to increase the reserved deformation and lining inner contour, and the deformation joint is encrypted, and the reinforced concrete structure is also configured to adopt a track structure, so that the monitoring measurement frequency can be improved in secondary lining construction.

In some embodiments, performing the preliminary grouting based on the reinforcement pile layout scheme includes: and cleaning each drilling gap or crack by using clear water for not less than a preset time.

The embodiments of the invention have at least the following beneficial effects: the method can fully utilize the combination of various detection means to detect, fully disclose the geological condition of the goaf, avoid potential hidden trouble caused by insufficient grouting in the grouting process, and form a good integral structure in the influence area of the goaf; the method can fully utilize the structure in the construction process, adopts the means of combining the detection and the irrigation, further utilizes the drilling of the reinforced piles to ascertain the breaking condition of the rock stratum in the construction process, dynamically adjusts the grouting reinforcement scheme in time, and ensures the reinforcement effect and the construction safety; on the premise of fully disclosing the geological condition of the goaf, the reinforcement pile can penetrate through the goaf crushing range for grouting, the penetration depth can be adjusted according to the detected parameters, and the stability of the lower part of the goaf after filling is ensured; the pressurized water test can wash the drilled holes and the stratum gap (fissure, solution gap or gap) channels, is favorable for slurry diffusion and cementing with surrounding rock, and improves grouting effect.

It should be understood that the description in this summary is not intended to limit the critical or essential features of the embodiments of the invention, nor is it intended to limit the scope of the invention. Other features of the present invention will become apparent from the description that follows.

Drawings

The above, as well as additional purposes, features, and advantages of embodiments of the present invention will become apparent in the following detailed written description and claims upon reference to the accompanying drawings. Several embodiments of the present invention are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which:

FIG. 1 is a schematic view of a lower goaf according to an exemplary embodiment of the present invention;

FIG. 2 is a plan view of a goaf substrate reinforcing grouting hole according to an exemplary embodiment of the present invention;

FIG. 3 is a cross-sectional view of goaf substrate reinforcement grouting in accordance with an exemplary embodiment of the present invention;

FIG. 4 is a schematic illustration of a grouting ring according to an exemplary embodiment of the present invention;

fig. 5 is a construction view of a steel flowtube according to an exemplary embodiment of the present invention;

like or corresponding reference characters indicate like or corresponding parts throughout the several views.

Detailed Description

Embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. While the invention is susceptible of embodiment in the drawings, it is to be understood that the invention may be embodied in various forms and should not be construed as limited to the embodiments set forth herein, but rather are provided to provide a more thorough and complete understanding of the invention. It should be understood that the drawings and embodiments of the invention are for illustration purposes only and are not intended to limit the scope of the present invention.

In describing embodiments of the present invention, the term "comprising" and its like should be taken to be open-ended, i.e., including, but not limited to. The term "based on" should be understood as "based at least in part on". The term "one embodiment" or "the embodiment" should be understood as "at least one embodiment". The terms "first," "second," and the like, may refer to different or the same object. Other explicit and implicit definitions are also possible below.

It should be understood that in the context of "tunnel", "section tunnel" and "tunnel section" express the same or similar concepts, and that in a particular scenario "section tunnel" and "tunnel section" may be a subset of "tunnel" or equivalent to the entire "tunnel" and thus may be used interchangeably in a particular scenario.

As mentioned above, grouting reinforcement means for the goaf and the overlying strata thereof are limited by the single monitoring means, so that insufficient grouting is easy to occur, and a good integral structure cannot be formed in the affected area of the goaf, so that the reinforcement effect is affected, and hidden danger is caused in the burying of tunnel engineering. Moreover, current solutions do not fully utilize existing structural configurations during the reinforcement process to dynamically adjust the construction solution to address the particular conditions that occur during the construction process. In addition, under the prerequisite that present reinforcement scheme can not fully reveal goaf geology condition, the reinforcement stake generally can not pass the broken scope of goaf pertinently, causes the goaf lower part after filling unstable enough, buries down construction potential safety hazard.

Aiming at the problems, the invention provides a scheme for reinforcing a mountain tunnel crossing a coal mine goaf, the position, depth, range and surrounding rock condition of the goaf can be explored through geological prediction and monitoring, and grouting reinforcement is carried out on the tunnel bottom from the inverted arch filling face downwards after the arrangement position of reinforcing piles and grouting proportion are adjusted according to engineering conditions. According to the scheme, the goaf surrounding rock structure is reinforced and strengthened more efficiently and fully, the goaf surrounding rock structure is filled with the mining overburden fracture zone and the bending zone rock mass separation layer and cracks, so that a rock plate structure with high rigidity and good integrity is formed, upward development of goaf collapse is effectively resisted, and tunnel operation safety is guaranteed. In addition, the scheme can fully utilize the structure in the construction process, adopts the means of combining the exploratory grouting, further utilizes the reinforced pile drilling to ascertain the rock stratum breaking condition in the construction, dynamically adjusts the grouting reinforcement scheme in time, and ensures the reinforcement effect and the construction safety; on the premise of fully disclosing the geological condition of the goaf, the reinforcement pile can penetrate through the goaf crushing range for grouting, the penetration depth can be adjusted according to the detected parameters, and the stability of the lower part of the goaf after filling is ensured; the pressurized water test can wash the drilled holes and the stratum gap (fissure, solution gap or gap) channels, is favorable for slurry diffusion and cementing with surrounding rock, and improves grouting effect.

An exemplary embodiment of the present invention will be described in detail with reference to fig. 1 to 5.

Fig. 1 is a schematic view of a lower goaf according to an exemplary embodiment of the present invention. In some embodiments, as shown in fig. 1, the goaf azimuth may be located at a position below the tunnel, specifically at a position of a downward fan centered at the tunnel center point. Therefore, in the tunnel construction process, in order to ensure construction safety, accurate detection is required to be performed on the goaf, and grouting reinforcement is performed according to detection results. Wherein the tunnel in the vicinity of the goaf may be referred to as a target tunnel section to be reinforced, in other words, the target tunnel section may at least partially span the goaf.

It should be noted that the location of the lower goaf in fig. 1 is merely exemplary, and the goaf may be located at other positions relative to the tunnel, such as a left-hand position or a right-hand position, which is not limited by the present invention.

In some embodiments, for goafs as shown in fig. 1, the goafs may be probed at the bottom of the target tunnel section based on one or more probing strategies in a set of preset probing strategies to obtain parameter information associated with the goafs, including information indicative of the crush range of the neighboring goafs. The preset detection strategy set can comprise transient electromagnetic method, drilling, comprehensive logging, in-hole television, cross-hole CT, sampling test and the like, and the parameter information can comprise the position, depth, range, surrounding rock condition and the like of the goaf. The information of the goaf breaking range may be, for example, information that the broken layer properties of the tunnel bottom can be represented, such as the size of the broken layer, the properties of the broken layer, and the like.

In some embodiments, the tunnel may be initially supported prior to probing. In one embodiment, tunnel construction can be performed by selecting a cross intermediate wall method or controlling blasting excavation so as to ensure stability and construction safety of surrounding rock, pipe shed advanced support is adopted, and full-ring steel frame can be adopted for primary support. In other embodiments, the construction may be performed by a step method or a double side wall pilot pit method, and the primary support may be performed by a method different from the cross-over intermediate wall method, which is not limited by the present invention.

In some embodiments, a reinforcement pile layout scheme for reinforcing the target tunnel section may be determined based at least on the parameter information and preliminary grouting may be performed based on the reinforcement pile layout scheme in which a plurality of reinforcement piles are arranged in a plurality of boreholes and in which at least a portion of the reinforcement piles pass through the goaf crushing range. In one embodiment, the reinforcing piles may be, for example, one or more of steel flower tubes or sleeve valve steel tubes.

In one embodiment, in particular, when the reinforcement pile is a steel pipe pile, a steel pipe pile arrangement scheme may be designed according to the detection situation. The arrangement principle can be as follows: the steel pipes are arranged in a quincuncial staggered manner; in a certain range of the end of the construction channel, in order to facilitate the formation of the grout stop wall as soon as possible, the grouting wall can be laid in an encrypted mode, and the other parts can be properly adjusted in layout density according to working conditions and detection results. In order to ensure the stability of the lower part of the goaf after filling, the steel pipe can pass through the goaf crushing range, the passing depth is determined by the goaf height and the coal pillar strength, for example, the steel pipe can be taken to be 2m, and in order to ensure the integral stability of the structure after reinforcing, the piles at the outermost side of the steel pipe can be arranged into inclined piles at a small angle.

In some embodiments, the goaf may be initially grouted. In one embodiment, the borehole may be subjected to a water-pressure test prior to the initial grouting to determine the permeability parameters of the formation in which the target tunnel section is located. In one embodiment, the permeation parameter may include, for example, one or more of a unit water absorption or a permeation coefficient value. Subsequently, one or more of a slurry material, a slurry concentration or water-to-solid ratio, a grouting pressure, a grouting speed, and a slurry diffusion range may be determined based on the permeation parameter, and an initial grouting regimen is determined based on one or more of the slurry material, the slurry concentration, the grouting pressure, the grouting speed, and the slurry diffusion range. Finally, an initial grouting scheme may be utilized to perform initial grouting.

In one embodiment, a pressurized water test may be performed on each borehole prior to initial grouting to flush the borehole and formation void (fissure, solution gap or void) channels, facilitating slurry diffusion and cementing with the surrounding rock, and improving grouting performance. The specific water absorption or permeability K value of the formation may then be calculated to understand the permeability of the formation to select the slurry material and its concentration and pressure. Further, the extent of slurry diffusion can be judged and used as a basis for single-hole grouting design and quality evaluation. In one embodiment, the drill holes may be rinsed with clear water for no less than 10 minutes prior to each initial grouting of the holes. In the rock stratum with easily deteriorated water-encountering performance, the flushing of gaps and cracks or the simple water-pressing test can be omitted before grouting.

In one embodiment, the unit water absorption w=q/LS may be calculated using w=q/LS, where formula: w may be the formation unit water absorption (L/min.m), Q may be the press-in flow (L/min), S may be the test pressure head (m), and L may be the pressure section length (m).

In one embodiment, when the water pressure test is carried out, the water level of the water pressure measuring hole and the water level of the adjacent drilling holes can be observed before water pressure, the water level change of the adjacent drilling holes is observed in the water pressure process, and the water levels of the water pressure drilling holes and the adjacent drilling holes (when the water pressure drilling holes are communicated with each other) and the descending speed of the water pressure drilling holes are observed after water pressure, so that the water pressure test process data are obtained, and the construction safety during the water pressure test is ensured.

In one embodiment, after the drilling reaches the designed depth, initial grouting can be performed, inspection can be performed after completion, the filling rate is not less than 70%, and the slurry mixing ratio and grouting pressure can be determined and adjusted according to field tests.

In some embodiments, the water-to-solid ratio of the slurry may employ 7 concentration ratio steps. According to engineering purpose and specific condition of construction site, 3 or 4 concentration ratio stages can be selected. When the goaf is filled with water, 3 or 4 concentration ratio stages with larger concentration can be adopted, and alternatively, the goaf can start from the ratio stage with thinner concentration. The slurry selecting mode fully considers engineering practice, and can adopt targeted slurry aiming at different crushing belts and crushing layers, thereby realizing the balance of treatment effect and engineering economy.

In some embodiments, the goaf crush zone may continue to be dynamically probed within the borehole during the initial grouting process to determine whether there is deviation information associated with the goaf crush zone, wherein the deviation information deviates from information indicative of an adjacent goaf crush zone. Subsequently, upon determining that there is a deviation from the information indicative of the extent of crush of the adjacent goaf, the initial grouting regime may be adjusted. Finally, goaf grouting can be continued based on the adjusted initial grouting scheme. Therefore, the structure in the construction process can be fully utilized, the rock stratum breaking condition can be further ascertained by utilizing the reinforced pile drilling in the construction, the grouting reinforcement scheme can be dynamically adjusted in time, and the reinforcement effect and the construction safety are ensured.

In one embodiment, the steel pipe pile may be constructed using a joint detection and grouting method. That is, the scale condition, the nature of the broken layer and the like of the tunnel bottom can be further ascertained by utilizing the steel pipe pile drilling in construction, and the reinforcing scheme can be timely adjusted when inconsistent with the design is found, so that the construction safety and the reinforcing effect are ensured. The drilling and grouting processes can be recorded in detail so as to comprehensively analyze grouting pressure and grouting speed.

In one embodiment, the grouting operation may be ended when the grouting pressure reaches a design final pressure value and is stable for 10min without grouting. In another embodiment, the grouting effect can be checked 28 days after the construction of the steel pipe pile is finished, methods such as drilling sampling, a water pressure test, a transient electromagnetic method, comprehensive well logging and the like are selected according to the field condition, and the grouting effect is good if the checking results all meet the specified requirements, so that the grouting design requirements are met.

In one embodiment, the goaf can be secondarily lined after the primary support deformation is stabilized, the secondary lining can be made of a reinforced concrete structure, the reinforced concrete structure can be configured to increase reserved deformation amount and lining inner contour, deformation joints of the reinforced concrete structure are encrypted, and the reinforced concrete structure can be made of a track structure, so that the structure can better cope with the deformation problem, and monitoring measurement frequency can be improved in secondary lining construction, so that deformation is always controlled in a safe range.

An exemplary specific engineering example of the scheme according to the present invention will be described below with reference to fig. 2 to 5. Wherein fig. 2 is a plan view of a goaf substrate reinforcement grouting hole in the engineering example according to an exemplary embodiment of the present invention, fig. 3 is a middle goaf substrate reinforcement grouting cross-sectional view of the engineering example according to an exemplary embodiment of the present invention, fig. 4 is a grouting cross-circle schematic diagram in the engineering example according to an exemplary embodiment of the present invention, and fig. 5 is a steel pipe construction diagram in the engineering example according to an exemplary embodiment of the present invention.

The engineering example belongs to a single-hole double-line mountain tunnel built in a certain city, a tunnel body YCK14+425-YCK14+855 section passes through a certain coal mine goaf, a +150m horizontal tunnel can exist in a protection range below a tunnel line, and the maximum height difference between the tunnel bottom and the goaf bottom plate is about 45m. After the goaf influence section is excavated and initially supported by a site construction unit, the goaf influence section is subjected to corresponding substrate detection work, and an old coal kiln roadway with the height of about 2m and filled with fine sand is accurately positioned near the elevation +260 of the goaf influence section, so that an area (YDK14+760-YDK14+780) needing grouting support in the target tunnel section is defined. After reasonable steel pipe arrangement and grouting scheme are designed according to detection conditions, grouting reinforcement is completed by a construction unit according to the sequence of steps of the construction method. And then drilling and sampling, and testing and checking by a pressurized water test, so that the filling effect is good, and the follow-up tunnel bottom settlement monitoring can also meet the goaf reinforcement safety requirement.

In the engineering example, specifically, the tunnel can be constructed by selecting a cross intermediate wall method, blasting excavation is controlled, a short advance rule is adopted for excavation, and the advance rule is 1.2m per cycle. The diameter of the cartridge is phi 32mm, and the apertures of the cut hole, the auxiliary hole, the bottom plate hole and the peripheral hole are all phi 40mm. The length of each circulation is 1.2m, and the depth of each hole is 1.5m.

In this embodiment, the number of the blast holes may be chosen to be 4 because of the low rock firmness factor. The spacing between the peripheral holes should be smaller than the common hole pitch, and is usually 500mm-700mm, for example, 500mm can be used. Wedge-shaped cutting is adopted, and the depth of the cutting hole can be 1.7m; the auxiliary eye spacing may be 0.6m to 0.8m, the resistance line may be 0.6m to 0.65m, and the hole depth may be 1.5m. The spacing between the peripheral eyelets can be 0.5m, the resistance line can be 0.6m, the hole depth can be 1.5m, and the peripheral eyelets are blasted; the cyclic footage of the construction drilling and blasting design can be 1.2m. The construction process can adopt pipe shed advanced support, and the primary support can adopt full-ring steel frame.

In this embodiment, after the primary support is completed, a borehole may be drilled at the bottom of the tunnel for substrate detection. The specific conditions of the goaf, including the position, depth, range, surrounding rock conditions and the like, are ascertained by comprehensive means such as drilling, comprehensive logging, in-hole television, cross-hole CT, sampling test and the like.

For the transient electromagnetic method, except for special regulations of geological profession, a measuring line is respectively arranged at the center line and the left and right 6m positions of the tunnel, and the maximum detection depth is 50m below the tunnel bottom plate. And (5) making original records of the detection line, the detection direction and the like, and drawing a multi-channel section view and a apparent resistivity section view of each detection line. The actually measured induced potential is subjected to data preprocessing, then the preprocessed data is subjected to inversion processing, finally, a contour map of a section of apparent resistivity is obtained, and the position of a cavity to be grouting is judged.

For the drilling method, after the primary support is finished, drilling and coring can be performed at the bottom of the tunnel, the drilling is strictly performed according to related operation rules and specifications, the drilling method can adopt a full-hole coring rotary drilling process, and the drill bit can adopt a diamond drill bit or a hard alloy drill bit; a common single-layer core tube drill bit can be adopted for the complete stratum; a double-layer core tube drill bit can be adopted for the soft and hard interbedding and the broken loose layer; and for the key positions of the characteristic layers of the overburden rock damage type of the goaf to be identified, double-layer core tubes can be adopted for continuous coring, and drilling is used for subsequent detection.

For the comprehensive logging method, in order to ensure the construction requirement, a host, a winch controller, a winch, a probe tube and the like are tested and checked before comprehensive logging according to the specification, so that the performance of the instrument meets the working requirement. And (3) carrying out comprehensive logging work on each drilling hole immediately after the drilling hole is finished according to the construction design requirement. The whole hole is used for measuring parameter curves such as potential resistivity, natural gamma, density, sound velocity and the like, measuring well diameter and well deviation, and the sampling interval can be 0.05m.

For the in-hole television method, in order to ensure good detection effect, hole washing work is carried out before the probe is put down, so that the wall of the hole is ensured to be clean. If water in the holes needs to be kept clear, if the water is turbid, a proper amount of alum can be added to clarify the water or the water in the holes can be pumped out. And (3) putting a probe into the hole, checking the image in the hole through a ground monitor, and observing the contents such as the change of formation lithology, the rock structure condition, the fracture shape, the filler property and the like.

For the cross-hole CT method, a transmitter and a receiver can be respectively placed in two holes, and the observation is performed by adopting a fixed-point emission mode, namely, the transmitter is fixed at a certain depth in the hole, and the receiver is moved in the other hole for measurement. And converting the differential distribution of electromagnetic wave energy caused by different lithology into a two-dimensional medium distribution image by using a tomography inversion algorithm, so as to infer the underground structural condition.

In this embodiment, as shown in fig. 2, 3 and 4, the steel pipe piles may be arranged by grouting the middle 76 steel pipe base, the grouting interval may be, for example, 1.5×1.5 plum blossom-shaped (see fig. 2 and 4), and the outermost 4 rows of piles may be arranged into inclined piles (see fig. 3) at 1 °, 3 °, 5 ° and 10 °, with the grouting depth not less than 1m below the pit bottom elevation of +260 roadway. As the steel pipe material, for example, hot rolled seamless steel pipe having a thickness of 76mm and a wall thickness of 4.5mm can be used. As shown in FIG. 5, grouting holes can be drilled on the pipe wall, the hole diameter can be 8-10 mm, the hole spacing can be 10-20 cm, and the pipe wall is arranged in a quincuncial shape. The front end of the steel pipe pile can be processed into a cone shape to form a cone head, and the tail length is not less than 150cm and is used as a reserved grout stop section without drilling.

In this embodiment, in the initial grouting of the goaf, a water-pressing test can be preferably performed on each drilling hole, and the purpose of the water-pressing test is to flush the drilling holes and the rock stratum gap (fissure, solution gap or gap) channels, so that slurry diffusion and cementing with surrounding rock are facilitated, and grouting effect is improved. The specific water absorption or permeability K value of the formation may then be calculated to understand the permeability of the formation to select the slurry material and its concentration and pressure. Further, the extent of slurry diffusion can be judged and used as a basis for single-hole grouting design and quality evaluation. And before grouting of each hole, the drilled holes can be washed by clean water, and the washing time is not less than 10min. In the rock stratum with easily deteriorated water-encountering performance, the flushing of gaps and cracks or a simple water-pressing test can be omitted before grouting.

In this embodiment, grouting can be performed after drilling reaches a designed depth, and after completion, the filling rate is checked to be not less than 70%, and the slurry mixing ratio and grouting pressure are determined according to field tests. The water-to-solid ratio of the slurry may be, for example, 7 concentration ratio stages of 5:1, 3:1, 2:1, 1:1, 0.8:1, 0.7:1, 0.6:1, etc. Specifically, 3 or 4 concentration ratio stages can be selected according to engineering purposes and specific conditions of construction sites. When the goaf is filled with water, 3 or 4 concentration ratio stages with larger concentration can be adopted, and conversely, the goaf starts from the ratio stage with thinner concentration.

In this embodiment, the steel pipe pile is constructed by adopting the method of combining the exploratory grouting and the grouting as described above, that is, the scale condition, the property and the like of the broken layer of the tunnel bottom should be further ascertained by drilling the steel pipe pile in the construction, and when the broken layer is found to be inconsistent with the design, the broken layer should be timely lifted for treatment, so that the safety is ensured, the drilling and grouting processes are all required to be recorded in detail, and the grouting pressure and the grouting speed are comprehensively analyzed. Grouting ending conditions: and when the grouting pressure reaches the design final pressure value and is stable for 10min without grouting, grouting can be finished.

Finally, the grouting effect can be checked. And (3) checking the grouting effect after the grouting is ended and finally set, and selecting methods such as drilling sampling, a pressurized water test, a transient electromagnetic method, comprehensive logging and the like according to the field condition, wherein the grouting effect can be considered to be good only when the checking results meet the specified requirements.

In the embodiment, when a transient electromagnetic method is adopted, according to a survey line arrangement scheme before grouting, a survey line is respectively arranged at the center line of a tunnel and the positions left and right close to the wall of the tunnel, a contour map of a apparent resistivity section is obtained, and the contour map is compared with the previous detection result to judge whether the cavity crack meets the filling requirement.

In the embodiment, when a drilling sampling method is adopted, grouting effect is checked 28 days after construction of the steel pipe pile is completed, drilling coring is performed at intervals of 5.0m to check whether grouting is full, and an unconfined compressive strength test is performed on a rock core, so that the bearing capacity of the composite foundation after grouting reinforcement is required to meet reinforcement requirements.

In this example, when the water pressure test method is adopted, the water pressure test can be performed through the inspection hole, ensuring that the water inflow is not more than 2L/min at a pressure of 1.0 MPa.

In this embodiment, when the comprehensive logging method is adopted, each parameter curve in the hole can be detected according to the measurement scheme before grouting, and the slurry filling effect can be judged.

And finally, carrying out secondary lining on the section tunnel to be reinforced. The secondary lining of the goaf can be poured after the primary support deformation is stable, the secondary lining adopts a reinforced concrete structure, the reserved deformation and the inner contour of the lining are increased, deformation joints are arranged in an encrypted mode, a track structure which can adapt to certain deformation is adopted, and monitoring and measuring frequency is increased during construction.

Therefore, the scheme of reinforcing the mountain tunnel crossing the coal mine goaf is utilized to realize the reinforcement treatment of the urban single-hole double-line mountain tunnel.

In conclusion, according to the embodiment of the invention, the position, depth, range and surrounding rock condition of the goaf can be explored through geological forecast and monitoring, and grouting reinforcement is performed on the tunnel bottom from the inverted arch filling face downwards after the arrangement position of the reinforcement piles and the grouting proportion are adjusted according to engineering conditions. According to the scheme, the goaf surrounding rock structure is reinforced and strengthened more efficiently and fully, the goaf surrounding rock structure is filled with the mining overburden fracture zone and the bending zone rock mass separation layer and cracks, so that a rock plate structure with high rigidity and good integrity is formed, upward development of goaf collapse is effectively resisted, and tunnel operation safety is guaranteed. In addition, the scheme can fully utilize the structure in the construction process, adopts the means of combining the exploratory grouting, further utilizes the reinforced pile drilling to ascertain the rock stratum breaking condition in the construction, dynamically adjusts the grouting reinforcement scheme in time, and ensures the reinforcement effect and the construction safety; on the premise of fully disclosing the geological condition of the goaf, the reinforcement pile can penetrate through the goaf crushing range for grouting, the penetration depth can be adjusted according to the detected parameters, and the stability of the lower part of the goaf after filling is ensured; the pressurized water test can wash the drilled holes and the stratum gap (fissure, solution gap or gap) channels, is favorable for slurry diffusion and cementing with surrounding rock, and improves grouting effect.

While several specific implementation details are included in the above discussion, these should not be construed as limiting the scope of the invention. Certain features that are described in the context of separate embodiments can also be implemented in combination in a single implementation. Conversely, various features that are described in the context of a single implementation can also be implemented in multiple implementations separately or in any suitable subcombination.

The foregoing description of embodiments of the invention has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the various embodiments described. The terminology used herein was chosen in order to best explain the principles of the embodiments, the practical application, or the technical improvements in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.

Claims (8)

1. A method for reinforcing a mountain tunnel crossing a goaf of a coal mine, the method comprising:

determining a target tunnel section to be reinforced along the tunnel, wherein the target tunnel section at least partially spans the goaf;

detecting the goaf at the bottom of the target tunnel section based on one or more detection strategies in a preset detection strategy set to obtain parameter information associated with the goaf, wherein the parameter information comprises information indicating a breaking range of the goaf adjacent to the goaf;

determining a reinforcement pile layout scheme for reinforcing the target tunnel section based on at least the parameter information, in which a plurality of reinforcement piles are arranged in a plurality of boreholes, and performing initial grouting based on the reinforcement pile layout scheme, at least a part of the reinforcement piles passing through the goaf crushing range and the passing depth being adjustable according to the detected parameter information;

continuing to dynamically detect the goaf crushing scope within the borehole during the initial grouting process to determine whether deviation information associated with the goaf crushing scope exists, wherein the deviation information is information that deviates from information indicating an adjacent goaf crushing scope;

upon determining that there is a deviation from the information indicative of the extent of goaf fragmentation adjacent the goaf, adjusting an initial grouting regime; and

continuing grouting the goaf based on the adjusted initial grouting scheme, and ending grouting process when grouting pressure reaches a design final pressure value and is stable for 10 minutes without grouting;

wherein determining a reinforcement pile layout scheme for reinforcing the target tunnel section based on at least the parameter information and performing initial grouting based on the reinforcement pile layout scheme includes:

performing a water-pressure test on each of the boreholes prior to the initial grouting to determine a permeability parameter of the formation in which the target tunnel section is located, the permeability parameter comprising one or more of a specific water absorption or a permeability coefficient value;

determining one or more of slurry material, slurry concentration or water-to-solid ratio, grouting pressure, grouting speed, and slurry diffusion range based on the permeation parameter;

determining the initial grouting scheme based on one or more of the slurry material, the slurry concentration, the grouting pressure, the grouting speed, and the slurry diffusion range; and

the initial grouting is performed using the initial grouting scheme.

2. The method according to claim 1, wherein the method further comprises:

the target tunnel interval is obtained by excavating by adopting a cross intermediate wall method, and blasting short footage excavation is controlled in the excavating process; and

and adopting a pipe shed for advanced support, and adopting a full-ring steel frame for primary support of the target tunnel section.

3. The method of claim 1, wherein the set of predetermined detection strategies comprises at least a transient electromagnetic method, a drilling method, a comprehensive well logging method, a television in-hole method, a cross-hole CT method, and a sampling test method; and/or

The parameter information also comprises the position, depth, range and surrounding rock conditions of the goaf; and/or

The reinforcing piles comprise one or more of steel flower pipes or sleeve valve steel pipes.

4. The method of claim 1, wherein the performing a pressurized water test on each of the boreholes prior to the initial grouting comprises:

before water pressing, observing the water level of a pressure measuring water hole and an adjacent drilling hole;

observing water level change of adjacent drilling holes in the water pressing process; and

after water is pressurized, the water levels of the pressurized water drilling holes and the adjacent drilling holes and the descending speed of the pressurized water drilling holes and the adjacent drilling holes are observed.

5. The method according to claim 1, wherein the unit water absorption is obtained based on the following equation W = Q/LS, wherein: w is the water absorption of the rock stratum unit, Q is the pressing flow, S is the test pressure head, and L is the length of the pressurized water section.

6. The method according to any one of claims 1 to 5, further comprising:

and (3) after the grouting process is finished, checking the grouting effect by using one or more methods of drilling sampling, a pressurized water test, a transient electromagnetic method and comprehensive logging until the checking result reaches the design requirement.

7. The method of claim 6, wherein the method further comprises:

and carrying out secondary lining on the goaf after the primary support deformation is stable, wherein the secondary lining adopts a reinforced concrete structure, the reinforced concrete structure is configured to increase the reserved deformation and lining inner contour, and the deformation joint is encrypted, and the reinforced concrete structure is also configured to adopt a track structure, and the monitoring measurement frequency is improved in secondary lining construction.

8. The method of claim 1, wherein performing an initial grouting based on the reinforcement pile layout scheme comprises:

and cleaning each drilling gap or crack by using clear water for not less than a preset time.

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