Ground segmented descending grouting method for broken andesitic basalt strata

Abstract

The present invention discloses a ground segmented downward grouting method for a broken andesitic basalt stratum, comprising the following steps: constructing a non-grouting section of an S borehole by using a drilling rig, and installing a casing in the non-grouting section of the S borehole; dividing the grouting section of the S borehole into a flower tube grouting section and a bare hole grouting section according to the degree of stratum fragmentation; constructing the flower tube grouting section of the S borehole by using a drilling rig; installing a flower tube in the flower tube grouting section of the S borehole, and filling casing material in the inner and outer spaces of the flower tube; after the casing material solidifies, performing segmented hole sweeping grouting from top to bottom along the flower tube grouting section of the S borehole; constructing the bare hole grouting section of the S borehole by using a drilling rig in segments, and after each bare hole grouting section is constructed, performing segmented grouting from top to bottom along the bare hole grouting section of the S borehole. The present invention can solve the problems that the slip-type grouting plug is easily stuck in the hole during the ground segmented downward grouting process of the broken andesitic basalt stratum and the easy grouting caused by multiple cracks in the surrounding rock of the stratum.

Description

Technical Field

[0001] The invention relates to the technical field of grouting in broken strata, and more particularly to a ground segmented downward grouting method for broken andesitic basalt strata. Background Art

[0002] In order to facilitate the construction and speed up the construction progress during the mine construction, it is usually necessary to construct a vertical shaft. If the rock mass of the stratum through which the vertical shaft is to be constructed is a broken stratum, such as a broken andesitic basalt stratum, this broken stratum usually contains underground aquifers such as bedrock fissure water and dissolution water; if no reinforcement treatment is performed, water gushing and other safety accidents may occur during the vertical shaft construction. At present, for this situation, during the vertical shaft construction, the shaft ground pre-grouting method is usually used to treat the aquifer. When using the wellbore ground pre-grouting method to seal and reinforce the aquifer in the broken stratum, the segmented downward grouting in the andesitic basalt broken stratum becomes a construction difficulty. In addition, since the slip-type grouting plug is often used to stop the grouting during grouting, and the slip-type grouting plug requires the rock at the seat to be intact and high in strength to achieve grouting, and the andesitic basalt stratum is broken and the rock integrity is poor, the grouting plug is frequently stuck in the borehole during the process of lifting and lowering the slip-type grouting plug, which makes it difficult to handle accidents and affects the construction period; therefore, segmented grouting is also a difficulty in the segmented downward grouting construction of the wellbore ground pre-grouting method. In addition, the reinforcement of broken strata in the prior art also adopts the bottom-up segmented perforation grouting process (patent CN111365002A) for reinforcement, but this method requires operations such as loading guns and detonation, has high construction costs, and poor construction safety, especially for broken strata, the perforation injection process produces greater disturbance to the broken strata. Summary of the invention

[0003] To this end, the technical problem to be solved by the present invention is to provide a method for ground-based segmented downward grouting in broken andesitic basalt formations, so as to solve the problems that the perforation grouting process used in the existing broken formation grouting causes great disturbance to the formation and has poor construction safety, as well as the difficulty in constructing the ground-based segmented downward grouting in broken andesitic basalt formations, and the slip-type grouting plug is easily stuck in the hole during the grouting process, and is easy to return to the grouting due to the multiple cracks in the surrounding rock of the formation.

[0004] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0005] The ground segmented descending grouting method for crushing andesitic basalt strata comprises the following steps:

[0006] Step A: construct the non-grouting section of the S borehole using a drilling rig, and install a casing in the non-grouting section of the S borehole;

[0007] Step B: According to the degree of fragmentation of the andesitic basalt stratum, the grouting section of the S borehole is divided into a flower tube grouting section and a bare hole grouting section; the surrounding rock grade of the flower tube grouting section is Class V, and the surrounding rock grade of the bare hole grouting section is less than or equal to Class IV;

[0008] Step C: constructing the floral tube grouting section of the S-bored hole by using a drilling machine; installing the floral tube in the floral tube grouting section of the S-bored hole, and filling the space inside and outside the floral tube with casing material; after the casing material solidifies, performing segmented hole sweeping grouting from top to bottom along the floral tube grouting section of the S-bored hole;

[0009] Step D: Use a drilling rig to construct the open hole grouting section of the S borehole in sections, and after the construction of each open hole grouting section is completed, perform section-wise grouting from top to bottom along the open hole grouting section of the S borehole.

[0010] In the above-mentioned ground segmented downward grouting method for the broken andesitic basalt stratum, the casing material is composed of water, ordinary silicate cement, microsilica powder, sodium silicate and sodium bentonite. In the casing material, ordinary silicate cement is a cementitious material, while the presence of microsilica powder can improve the stability of the casing material, sodium silicate can shorten the initial setting time of the casing material, and sodium bentonite can improve the stability of the casing material and control the compressive strength of the stone body.

[0011] In the above-mentioned ground segmented downward grouting method for the broken andesitic basalt stratum, the mass ratio of water, ordinary Portland cement, microsilica powder, sodium silicate and sodium-based bentonite is 1:0.3:0.02:0.02:0.06; the ordinary Portland cement is P.O42.5 cement; the average particle size of the microsilica powder is less than 0.1um, and the specific surface area is 15-20m 2 / g. When the mass ratio of water, ordinary silicate cement, microsilica powder, sodium silicate and sodium bentonite in the casing material is 1:0.3:0.02:0.02:0.06, the funnel viscosity of the casing material is 59s, the 2h water separation rate is 0, the initial setting time is 4h, and the 3d unconfined compressive strength is 1MPa~2MPa. The mud stone body formed after the casing material solidifies can fix the flower tube in the deep broken basalt formation, and the stone body in the annular space between the flower tube wall and the borehole wall can be split under the grouting pressure greater than 7MPa, realizing the grouting effect of the grouting slurry diffusing into the formation.

[0012] In the above-mentioned ground segmented descending grouting method for the broken andesitic basalt stratum, in step C, the segmented sweeping hole grouting method from top to bottom along the flower tube grouting section of the S borehole is as follows:

[0013] Step (C-1): Divide the floral tube grouting section from top to bottom into two or more floral tube grouting section segments, which are the first floral tube grouting section, the second floral tube grouting section ... the Nth floral tube grouting section from top to bottom, where N is a positive integer, and the segment height of each floral tube grouting section is 25 to 35 m;

[0014] Step (C-2): Sweep the hole to the lowest end of the first flower tube grouting section according to the preset section height, and then lower the slip-type grouting plug for grouting; when the grouting reaches the end standard, fill the first annular space between the flower tube wall and the borehole wall of the first flower tube grouting section with cement slurry with a water-cement ratio of 0.8:1, and maintain until a cement slurry stone body is formed in the first annular space; the cement slurry stone body formed in the first annular space can realize permanent blocking of the first annular space of the first flower tube grouting section, creating better grouting conditions for the second flower tube grouting section;

[0015] Step (C-3): Sweep the hole to the lowermost end of the second flower tube grouting section according to the preset section height, then lower the slip stopper to a position adjacent to the bottom of the first flower tube grouting section, and perform grouting; when the grouting reaches the end standard, fill the second annular space between the flower tube wall and the borehole wall of the second flower tube grouting section with cement slurry having a water-cement ratio of 0.8:1 (that is, the mass ratio of water to ordinary Portland cement is 0.8:1. If the water-cement ratio is greater than 0.8, the cement slurry has a low solidification rate and the annular space is not densely filled; if the water-cement ratio is less than 0.8, the cement slurry will have a high specific gravity and high viscosity, and the cement slurry will not be easy to diffuse), and maintain until a cement slurry stone body is formed in the second annular space; repeat this cycle until the grouting of the Nth flower tube grouting section is completed and a cement slurry stone body is formed in the Nth annular space.

[0016] In the above-mentioned ground segmented downward grouting method for the broken andesitic basalt formation, in step A, the specification of the casing is Φ177.80mm×8.05mm; in step C, the borehole diameter of the flower tube grouting section is 152.4mm, and the specification of the flower tube is Φ139.70mm×6.20mm; the solidification time of the casing material is 70-75h; and the curing time for forming the cement slurry stone body in the first annular space, the second annular space...the Nth annular space is 70-75h.

[0017] In the above-mentioned ground segmented descending grouting method for the broken andesitic basalt formation, in step D, the method of performing segmented grouting from top to bottom along the open hole grouting section of the S borehole is:

[0018] Step (D-1): Divide the open hole grouting section into two or more open hole grouting sections from top to bottom, which are the first open hole grouting section, the second open hole grouting section ... the Mth open hole grouting section from top to bottom, where M is a positive integer and the height of each open hole grouting section is 25 to 35 m;

[0019] Step (D-2): constructing the first open hole grouting section using a drilling rig, then placing a slip-type grouting plug at the bottom of the adjacent flower pipe section and performing grouting;

[0020] Step (D-3): Use a drilling rig to construct the second open hole grouting section, lower the slip stopper to the bottom of the adjacent first open hole grouting section, and perform grouting; repeat this cycle until the grouting of the Mth open hole grouting section is completed.

[0021] In the above-mentioned ground segmented downward grouting method for the broken andesitic basalt formation, the borehole diameter of the open hole grouting section is 117.5 mm.

[0022] In the above-mentioned ground segmented downward grouting method for broken andesitic basalt formation, in steps C and D, the grouting slurry used in the flower tube grouting section is mixed with water and ordinary Portland cement in a mass ratio of 0.8 to 1.5:1; the ordinary Portland cement is P.O42.5 cement.

[0023] In the above-mentioned ground segmented downward grouting method for the broken andesitic basalt formation, in step D, when grouting the open hole grouting section, first construct a Φ117.5mm grouting borehole, and lower a Φ115mm slip-type grouting plug to stop the grouting; if the grouting cannot be stopped, then expand the hole to Φ133mm, and lower a Φ125mm slip-type grouting plug for testing; if the grouting still cannot be stopped, then expand the hole to Φ152.4mm, and lower a Φ140mm grouting plug for testing; when the grouting test fails, first inject a single-liquid cement slurry to solidify for 50 to 70 minutes, then lift the grouting plug out of the hole, and after solidification for 72 hours, lower the grouting plug again for the grouting test.

[0024] In the above-mentioned ground segmented downward grouting method for the broken andesitic basalt formation, the single-liquid cement slurry is mixed with water and ordinary Portland cement in a mass ratio of 0.8 to 1.5:1; the ordinary Portland cement is P.O42.5 cement.

[0025] The technical solution of the present invention achieves the following beneficial technical effects:

[0026] According to the fragmentation of andesitic basalt strata, the present invention divides the grouting section into a flower tube grouting section and an open hole grouting section, wherein the grouting section with a lower degree of fragmentation adopts open hole grouting, and the grouting section with a higher degree of fragmentation adopts the method of installing flower tubes and filling casing materials for hole sweeping grouting; this grouting method can save the construction amount to the greatest extent, and the present invention adopts a top-down segmented downward grouting method, which can effectively prevent the stuck drill hole phenomenon caused by the large degree of stratum fragmentation during the process of raising and lowering the stop plug, thereby improving the grouting construction efficiency. In addition, the segmented downward grouting method for crushing andesitic basalt strata on the ground of the present invention can effectively avoid the problems of large stratum disturbance, high construction cost and poor construction safety in the segmented perforation grouting process.

[0027] At the end of the segmented downward grouting of the flower tube grouting section, the present invention forms a cement slurry stone body by leaving cement slurry with a water-cement ratio of 0.8:1 in the annular space between the flower tube wall and the borehole wall of each flower tube grouting section. The cement slurry stone body in the annular space can effectively prevent the slurry of the next flower tube grouting section from returning, thereby creating a slurry stopping condition for the next flower tube grouting section. At the same time, a slurry stopping plug can also be installed in the flower tube, which can effectively avoid the difficulty of slurry stopping by the slip-type slurry stopping plug due to the high degree of stratum fragmentation and poor stability of the hole wall, and at the same time avoid the problem of easy slurry return due to multiple cracks in the surrounding rock of the stratum.

[0028] The present invention controls the ratio of the components in the casing material, and controls the setting time and stone body strength of the casing material, so that the stone body formed after the casing material sets can be split by the grouting slurry in the present invention under a certain pressure during grouting, and can also provide a certain supporting force along the drilling direction, thereby effectively controlling the grouting section height. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A design diagram of the ground pre-grouting drilling trajectory of the vertical shaft in the embodiment of the present invention;

[0030] Figure 2 A picture of andesitic basalt core in the stratum traversed by the vertical shaft in the embodiment of the present invention;

[0031] Figure 3 Schematic diagram of the slurry return process in the embodiment of the present invention;

[0032] Figure 4 Schematic diagram of downward-type segmented grouting in an embodiment of the present invention;

[0033] Figure 5 A schematic structural diagram of the flower tube used in an embodiment of the present invention. DETAILED DESCRIPTION

[0034] This embodiment further illustrates the grouting method of the present invention by taking the construction of a vertical shaft during the construction of the Xianglushan Tunnel of the Dianzhong Water Diversion Project as an engineering test.

[0035] 1. Project Overview

[0036] The Dianzhong Water Diversion Project consists of two parts: the water source project and the water delivery project. The water source project is located in Shigu Town, Yulong County; the water delivery project starts from Wangchengpo, Shigu Town, Lijiang, passes through Lijiang City, Dali Prefecture, Chuxiong Prefecture, Kunming City, Yuxi City, and ends at Xinpobei, Honghe Prefecture. The Xianglu Mountain Tunnel is the controlling project of the Dianzhong Water Diversion Project, and the Dali Section I Construction No. 2 is the key section for the full connection of the Xianglu Mountain Tunnel. Among them, the 4# and 5# construction branch tunnels and the main tunnel drilling and blasting section and TBMa-2 section they control are the key lines in the key section. Due to the influence of various factors, the construction period of the 4# and 5# construction branch tunnels has been delayed. In the construction of the tunnel project, adding tunnel headings and realizing long tunnel short-distance driving are effective measures to catch up with the construction period, so the design change added a vertical shaft between the pile numbers of the 4# and 5# construction branch tunnels.

[0037] 2. Shaft geology and hydrogeology

[0038] The vertical shaft passes through the strata from top to bottom, including Quaternary residual slope soil with broken rocks, the upper section of the Beiya Formation of the Middle Triassic (T 2 b 2 ) Gray, light gray limestone, dolomite limestone, dolomite and Tertiary intrusive rocks (Nβ) gray interbedded with dark purple and gray-brown andesitic basalt.

[0039] (1) In the upper part of the well body (K0~K0+174), the surface vegetation is sparse, the terrain slope is 10°~25°, and the surface is a gentle platform. The surface layer is distributed with Quaternary residual slope silty clay mixed with broken stones, with a thickness of 8m~12m and a loose structure. The underlying bedrock is (T 2 b 2 ) Strongly eroded and weathered limestone and dolomite limestone, affected by faults, are mostly breccia and granular rock belts. Due to the influence of erosion, weathering and structural compression, the rock mass has poor integrity and developed cracks; the surrounding rock is Class V and Class IV. The shaft pile number K0+000~K0+074 section is located above the groundwater level; the groundwater is mainly bedrock fissure water~dissolution water, and the maximum water level of the pile number K0+074~K0+174 section is 100m deep. According to the estimation of the water inflow of the shaft, the water inflow is about 240~2682m 3 / d, is the water inrush level.

[0040] (2) The middle section of the wellbore (K0+174~K0+350), with a burial depth of 174~350m, is surrounded by weakly eroded and weathered limestone and dolomitic limestone. Some sections are significantly affected by fault structures and are fault breccia and granular rock. They are mainly eroded and weathered along the fissures and some fault fracture zones. The rock mass is generally relatively intact to relatively broken. The surrounding rock is mainly Class IV, with Class III. The groundwater is mainly bedrock fissure water and karst water. The maximum water level drop in this section is 276m. According to the estimation of the water inflow of the vertical shaft, the water inflow is about 2167~6482m 3 / d, is the water inrush level.

[0041] (3) The rear section of the wellbore (K0+350~K0+565.25), with a burial depth of 350~565.25m, is surrounded by andesitic basalt. Fault breccia and crushed silt are seen in some sections. It is mainly soft rock to medium hard rock. The rock mass is broken and the surrounding rock is Class V with Class IV. The groundwater is mainly bedrock fissure water. The maximum water level drop is about 492m. According to the estimation of the water inflow of the vertical shaft, the water inflow is about 2778~5516m 3 / d, is the water inrush level.

[0042] In this embodiment, the classification of surrounding rock is carried out according to the classification standard in the Technical Specification for Rock and Soil Anchor and Shotcrete Support Engineering GB50086-2015.

[0043] 3. Design of pre-grouting on the ground of vertical shaft

[0044] In order to ensure the safe and rapid excavation of the vertical shaft, the ground pre-grouting method is used to block the gushing water and reinforce the stratum. The starting and ending depths of the ground pre-grouting are 70m to 580m. The ground pre-grouting design of straight hole + S hole is adopted. The S hole grouting construction process is parallel to the upper well drilling, which can speed up the construction of the vertical shaft. The starting and ending depths of the straight hole grouting are 70m to 360m, and the strata to be treated are limestone, dolomite limestone and boundary strata; the starting and ending depths of the S hole grouting are 360m to 580m, and the strata to be treated are boundary strata and andesitic basalt. The ground segmented downward grouting method for crushing andesitic basalt strata in this embodiment includes the following steps:

[0045] Step A: Divide the S borehole into a non-grouting section and a grouting section, use a drilling rig to construct the non-grouting section of the S borehole, and install casing in the non-grouting section of the S borehole; the installation depth of the Φ177.80mm×8.05mm casing of the S hole is 360m (0~360m is the non-grouting section of the S hole), see Figure 1 ;

[0046] Step B: According to the degree of formation fragmentation, the grouting section of the S borehole is divided into a flower tube grouting section and a bare hole grouting section; the surrounding rock grade of the flower tube grouting section is Class V (360-450m), and the surrounding rock grade of the bare hole grouting section is Class IV (450-580m);

[0047] Step C: constructing the floral tube grouting section of the S-bored hole by using a drilling machine; installing the floral tube in the floral tube grouting section of the S-bored hole, and filling the space inside and outside the floral tube with casing material; after the casing material solidifies, performing segmented hole sweeping grouting from top to bottom along the floral tube grouting section of the S-bored hole;

[0048] Step D: Use a drilling rig to construct the open hole grouting section of the S borehole in sections, and after the construction of each open hole grouting section is completed, perform section-wise grouting from top to bottom along the open hole grouting section of the S borehole.

[0049] 4. Analysis of problems in S-hole grouting

[0050] The commonly used grouting stopper for ground pre-grouting is the slip-type grouting stopper. The slip-type grouting stopper requires the rock at the seat to be intact and high in strength. However, the andesitic basalt stratum is broken, such as Figure 2 As shown in the figure, segmented grouting becomes the main problem of S-hole grouting.

[0051] 5. S-hole segmented downward grouting method

[0052] 5.1 Downward grouting method for Class IV surrounding rock (open hole grouting section)

[0053] The rock integrity of the stratum in the 450m-580m section is relatively high, and it is Class IV surrounding rock, and its grouting condition is slightly better; the construction method of the open hole grouting section in the 450m-580m section is: construct a Φ117.5mm drill hole, and carry out open hole segmented downward grouting construction, such as Figure 4 (Ⅳ) as shown; first drill to 480m, then lower the slip stop plug at about 450m, then carry out grouting from 450m to 480m, and after reaching the grouting end standard; continue drilling to 510m, lower the slip stop plug at about 480m, then carry out grouting from 480m to 510m, and repeat this cycle until the segmented downward grouting construction of the bare hole section is completed; the grouting slurry in this section is a mixture of water and ordinary Portland cement in a mass ratio of 1:1 to 0.8:1; the ordinary Portland cement is P.O42.5 cement.

[0054] (1) The driller should record the drilling speed in detail and analyze the hardness of different layers. In high-strength formations, directional drilling should be avoided as much as possible to keep the borehole in a true circular state. During normal drilling, the drilling speed should be low to avoid excessive speed that would enlarge the hole wall.

[0055] (2) First, construct a Φ117.5mm grouting hole, and lower a Φ115mm slip-type grouting plug to stop the grouting. If the grouting cannot be stopped, expand the hole to Φ133mm, and lower a Φ125mm slip-type grouting plug for testing. If the grouting cannot be stopped, expand the hole to Φ152.4mm, and lower a Φ140mm grouting plug for testing to increase the probability of effective grouting.

[0056] (3) In some cases, the slurry flows through the cracks to the upper part of the stop plug and then flows back. Figure 3 In the case of grouting, inject single-liquid cement slurry (single-liquid cement slurry is a mixture of water and ordinary Portland cement in a mass ratio of 1:1; ordinary Portland cement is P.O42.5 cement) for about 1 hour, and then promptly remove the grouting plug from the hole to reinforce the formation. After 72 hours of setting, lower the grouting plug again to stop the grouting.

[0057] (4) After the stop plug is sealed, the stop effect is usually tested by water pressure. In the case of a small amount of return slurry, it is mostly caused by the water flowing through the micro cracks. Figure 3 As shown, the water pressure test for stopping grouting effect can be changed to clay slurry pressure test.

[0058] (5) When the grouting slurry is clay cement slurry, the grouting can be continued for about 8 hours if the amount of return slurry is small. The stop plug can still be released normally and safely removed from the hole.

[0059] 5.2 Downward grouting method for Class V surrounding rock (flower tube grouting section)

[0060] For highly broken strata, the above measures cannot effectively stop the grouting, so the method of installing a flower pipe in the broken strata is used to perform segmented downward grouting. In this embodiment, the strata in the 360m to 450m section of the borehole are severely broken, the hole wall stability is poor, and it is difficult to stop the grouting. Therefore, the flower pipe is first installed to fill the casing material and then the segmented sweeping hole grouting is performed from top to bottom.

[0061] The specific method is: first construct a Φ152.4mm drill hole to 450m, such as Figure 4 (I); Install Φ139.70mm×6.20mm flower tube in the section of 360m~450m, such as Figure 4 (Ⅱ); Flower tube structure such as Figure 5 As shown in the figure, the shell material is used (water, ordinary Portland cement, microsilica powder, sodium silicate, sodium bentonite are mixed in a mass ratio of 1:0.3:0.02:0.02:0.06; the ordinary Portland cement is P.O42.5 cement; the average particle size of the microsilica powder is less than 0.1um, and the specific surface area is 15-20m 2 / g; the funnel viscosity of the shell material is 59s, the 2h water separation rate is 0, the initial setting time is 4h, and the 3d unconfined compressive strength is 1MPa~2MPa. The stone body formed after the shell material solidifies can fix the flower tube in the deep broken basalt formation, and the stone body in the annular space between the flower tube wall and the borehole wall can be split under the grouting pressure greater than 7MPa, achieving the effect of grouting slurry diffusion into the formation); fill the inner and outer spaces of the Φ139.70mm flower tube, and after solidification for about 72h, carry out hole sweeping grouting. According to the 30m section height, downward grouting construction is carried out: first, the hole is swept to 390m, and the slip-type grouting plug is lowered to grout the 360m-390m section. The grouting slurry is a mixture of water and ordinary Portland cement in a mass ratio of 1:1 to 0.8:1; ordinary Portland cement is P.O42.5 cement; the grouting slurry will crush the solidified casing material in the annular space between the flower tube wall and the borehole wall and enter the formation. When the grouting reaches the end standard, the water-cement ratio of the grouting slurry is controlled to 0.8:1, that is, The annular space between the wall of the flower tube and the wall of the borehole in the flower tube grouting section is filled with cement slurry with a water-cement ratio of 0.8:1, and cured for 72 hours until a cement slurry stone body is formed in the annular space; the cement slurry stone body in the annular space can prevent the slurry from returning to the borehole when the slurry is stopped at the 390m position; then the hole is swept to 420m, and the slurry is sealed at about 390m using a slip-type slurry stop plug to carry out grouting in the 390m-420m section, and then the same method is used to carry out the hole sweeping grouting in the 420m-450m section.

[0062] 6. Methods to avoid accidents caused by grout plugging in grouting holes

[0063] In this embodiment, the andesitic basalt formation is broken and the rock integrity is poor. During the process of raising and lowering the slip-type grouting plug, the grouting plug is frequently stuck in the borehole, which makes it difficult to handle the accident and affects the construction period for a long time. The slip-type grouting plug tests the grouting position in the borehole. During each grouting process, the three slips of the grouting plug expand outward and squeeze the formation. After the grouting test fails, the grouting plug needs to be smashed down and the grouting position needs to be found again. During this process, some rock chips will fall on the upper part of the grouting plug, which will jam the grouting plug or the grouting plug can only move down but not up. In response to this situation, technical means have been developed to avoid accidents of grouting plugs in the hole.

[0064] (1) Select the optimal slip-type grout plug for different borehole diameters; check the integrity of each component of the grout plug before lowering it each time.

[0065] (2) Before lowering the stop plug each time, mix the drilling mud to ensure the performance of the mud in the borehole and maintain the stability of the hole wall.

[0066] (3) Test the stop plug position in the open hole. After each stop test, connect the mud pump to circulate the drilling mud and carry the rock cuttings out of the hole until no more rock cuttings appear on the vibrating screen that filters the mud. Then conduct the next stop test.

[0067] During the grouting construction of the S-holes on the ground of the Xianglushan Tunnel vertical shaft, the above-mentioned grouting method was used to reduce the occurrence of accidents in the hole, improve construction efficiency, and ensure the smooth construction of the project.

Claims

1. A ground-level segmented downward grouting method for crushing andesitic basalt strata, characterized in that: The steps include: Step A: construct the non-grouting section of the S borehole using a drilling rig, and install a casing in the non-grouting section of the S borehole; Step B: According to the degree of fragmentation of the andesitic basalt stratum, the grouting section of the S borehole is divided into a flower tube grouting section and a bare hole grouting section; the surrounding rock grade of the flower tube grouting section is Class V, and the surrounding rock grade of the bare hole grouting section is less than or equal to Class IV; Step C: constructing the floral tube grouting section of the S-bored hole by using a drilling machine; installing the floral tube in the floral tube grouting section of the S-bored hole, and filling the space inside and outside the floral tube with casing material; after the casing material solidifies, performing segmented hole sweeping grouting from top to bottom along the floral tube grouting section of the S-bored hole; Step D: Use a drilling rig to construct the open hole grouting section of the S borehole in sections, and after the construction of each open hole grouting section is completed, perform section-wise grouting from top to bottom along the open hole grouting section of the S borehole; The casing material is composed of water, ordinary Portland cement, microsilica fume, sodium silicate and sodium bentonite; the mass ratio of water, ordinary Portland cement, microsilica fume, sodium silicate and sodium bentonite is 1:0.3:0.02:0.02:0.06; ordinary Portland cement is P.O42.5 cement; the average particle size of microsilica fume is less than 0.1um, and the specific surface area is 15-20m 2 / g; the mud stone body formed after the casing material solidifies fixes the flower tube in the deep broken basalt formation, and the stone body in the annular space between the flower tube wall and the borehole wall is split under the grouting pressure greater than 7MPa, achieving the grouting effect of the grouting slurry diffusing into the formation; In step C, the segmented hole sweeping grouting method from top to bottom along the flower tube grouting section of the S borehole is: Step (C-1): Divide the floral tube grouting section from top to bottom into two or more floral tube grouting section segments, which are the first floral tube grouting section, the second floral tube grouting section, ... the Nth floral tube grouting section, N is a positive integer, and the height of each floral tube grouting section is 25 to 35 m; Step (C-2): Sweep the hole to the lowest end of the first flower tube grouting section according to the preset section height, and then lower the slip-type grouting plug to perform grouting; when the grouting reaches the end standard, fill the first annular space between the flower tube wall and the borehole wall of the first flower tube grouting section with cement slurry having a water-cement ratio of 0.8:1, and maintain until a cement slurry stone body is formed in the first annular space; Step (C-3): sweep the hole to the lowermost end of the second flower tube grouting section according to the preset section height, then lower the slip stopper to a position adjacent to the bottom of the first flower tube grouting section, and perform grouting; when the grouting reaches the end standard, fill the second annular space between the flower tube wall and the borehole wall of the second flower tube grouting section with cement slurry having a water-cement ratio of 0.8:1, and maintain until a cement slurry stone body is formed in the second annular space; repeat this cycle until the grouting of the Nth flower tube grouting section is completed, and a cement slurry stone body is formed in the Nth annular space; The specification of the casing is Φ177.80mm×8.05mm; in step C, the borehole diameter of the flower tube grouting section is 152.4mm, and the specification of the flower tube is Φ139.70mm×6.20mm; the solidification time of the casing material is 70 to 75h; the curing time for forming the cement slurry stone body in the first annular space, the second annular space...the Nth annular space is 70 to 75h.

2. The ground segmented descending grouting method for broken andesitic basalt strata according to claim 1 is characterized in that: In step D, the method of performing top-down segmented grouting along the open hole grouting section of the S borehole is as follows: Step (D-1): Divide the open hole grouting section into two or more open hole grouting sections from top to bottom, which are the first open hole grouting section, the second open hole grouting section ... the Mth open hole grouting section from top to bottom, where M is a positive integer and the height of each open hole grouting section is 25 to 35 m; Step (D-2): construct the first open hole grouting section using a drilling rig, then place the slip-type grouting plug at the bottom of the adjacent flower pipe section and perform grouting; Step (D-3): Use a drilling rig to construct the second open hole grouting section, lower the slip-type grouting plug to the bottom of the adjacent first open hole grouting section, and perform grouting; repeat this cycle until the grouting of the Mth open hole grouting section is completed.

3. The ground segmented descending grouting method for broken andesitic basalt strata according to claim 2 is characterized in that: The borehole diameter of the open hole grouting section is 117.5 mm.

4. The ground segmented descending grouting method for broken andesitic basalt strata according to claim 1 is characterized in that: In steps C and D, the grouting slurry used in the floral pipe grouting section is mixed with water and ordinary Portland cement in a mass ratio of 0.8 to 1.5:1; the ordinary Portland cement is P.O42.5 cement.

5. The ground segmented descending grouting method for broken andesitic basalt strata according to claim 1 is characterized in that: In step D, when grouting the open hole grouting section, first construct a Φ117.5mm grouting drill hole, and lower a Φ115mm slip-type grouting plug to stop the grouting; if the grouting cannot be stopped, then expand the hole to Φ133mm, and lower a Φ125mm slip-type grouting plug for testing; if the grouting still cannot be stopped, then expand the hole to Φ152.4mm, and lower a Φ140mm grouting plug for testing; when the grouting test fails, first inject single-liquid cement slurry to solidify for 50 to 70 minutes, then lift the grouting plug out of the hole, and lower the grouting plug again after solidification for 72 hours to carry out the grouting test.

6. The ground segmented descending grouting method for broken andesitic basalt strata according to claim 5 is characterized in that: The single-liquid cement slurry is prepared by mixing water and ordinary Portland cement in a mass ratio of 0.8 to 1.5:1; the ordinary Portland cement is P.O42.5 cement.

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