Grouting reinforcement and rapid excavation construction method for small-clear-distance tunnel in high-water-level area

Abstract

The invention provides a grouting reinforcement and rapid excavation construction method for a small-clear-distance tunnel in a high-water-level area. The grouting reinforcement and rapid excavation construction method comprises the following steps that (1) an interval tunnel is excavated through a CRD method, and earthwork is excavated in each pilot tunnel according to a benching method; (2) after the whole tunnel face is excavated to the grout stopping wall, the tunnel face is closed in time; (3) grouting is temporarily set as a 20m cycle in the tunneling direction of the tunnel, a 3m water stop disc is formed, full-section grouting and a retreating type grouting process are carried out in the sequence of outside-to-inside spaced jump hole grouting, and grouting of the next cycle is completed; the deformation influence of grouting on a tunnel gap stratum and an adjacent tunnel is reduced, it is ensured that soil bodies of a tunnel face and an arch part are stable when the tunnel is excavated, and therefore tunnel grouting and excavation construction can be efficiently, accurately and safely completed.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnel construction, and particularly to a grouting reinforcement and rapid excavation construction method for small clear distance tunnels in high water level areas. Background Technique

[0002] During the construction of tunnel and other chamber structures, complex geological conditions are often encountered, such as ground fissures, goafs, karst caves and sinkholes. Especially the ground fissures formed and developed based on the development of fault structures and induced by excessive groundwater extraction seriously affect the stability of the tunnel lining structure. Specifically, after the upper and lower plates of the strata on both sides of the ground fissure are displaced relative to each other, the settlement displacements of the tunnel lining structure in the strata and the soil on both sides of the ground fissure are different, which may lead to the separation of the lining structure from the surrounding rock. At the same time, under the action of ground fissure activities, additional stresses and additional deformations will be generated in the tunnel lining structure. Excessive additional deformations may lead to structural cracking or yield failure. In addition, the soil in the deformation zone of the ground fissure has many cracks and poor engineering properties. Local collapses of the foundation pit wall or the tunnel may occur during construction and operation, and concentrated water seepage along the crack zone may also occur, which will cause loess collapsibility deformation and uneven settlement, further exacerbating the damage of the tunnel lining structure; groundwater seeps into the tunnel along the cracks, affecting the normal operation of the tunnel.

[0003] A Chinese patent discloses an asphalt concrete composite lining for ground fissure tunnels. In the affected area of the ground fissure, an initial lining, an asphalt concrete composite lining, and an inner lining are arranged in sequence from the surrounding rock soil to the tunnel axis. The inner lining is provided with deformation joints A at intervals along the tunnel axis. Grouting holes are reserved at the bottom of the inner lining on both sides of the deformation joint A, and displacement monitors are installed outside the asphalt concrete composite lining. The present invention also discloses a support method for the above-mentioned asphalt concrete composite lining of the ground fissure tunnel, which adopts the bench-by-step excavation and the mining construction method. The modified asphalt is melted and mixed with sand and stones to make an asphalt concrete pouring material; the deformation joint A is filled with asphalt mastic material to flexibly connect adjacent two sections of the inner lining, and the construction joints of the inner lining section are waterproofed, etc. However, its support strength is low, and it cannot adapt to deformation, resulting in potential quality and safety hazards. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a grouting reinforcement and rapid excavation construction method for small clear distance tunnels in high water level areas to solve the problems raised in the above background technique.

[0005] The technical problem solved by the present invention is achieved by the following technical solutions: A grouting reinforcement and rapid excavation construction method for small clear distance tunnels in high water level areas includes the following steps:

[0006] Step (1). The interval tunnel is excavated by the "CRD" method, and the soil is excavated by the bench method in each pilot tunnel;

[0007] Step (2). After the entire heading face is excavated to the grouting stop wall, promptly seal the heading face.

[0008] Step (3). The grouting is tentatively set as one cycle every 20 m along the tunnel driving direction to form a 3-m water-stop disk. The full-section grouting is carried out in the order of first outside and then inside, with alternate and skip-hole grouting, using the backward grouting process. After the next cycle of grouting is completed;

[0009] Step (4). Adjust the grouting length in a timely manner according to the actual on-site grouting effect. During the grouting process, strengthen the observation at the heading face and prepare a certain amount of emergency rescue materials. Strengthen the monitoring of the ground surface and buildings during the grouting process to ensure the safety of the underground excavation construction and the ground surface buildings.

[0010] Furthermore, the grouting hole layout is included in the step (3). Before grouting, it is necessary to first carry out the work of measuring and setting out the lines, outline the area to be reinforced, mark the specific position of each hole according to the grouting design drawing, and mark it with red paint.

[0011] Furthermore, the grouting hole layout includes the setting of the grouting hole spacing. The grouting reinforcement range is 2.0 m outside the initial support contour line of the tunnel. The diameter of the grouting hole is Φ42 mm. The circumferential and radial spacing of the grouting holes in the advanced tunnel is 1.0 - 1.5 m. Considering that the grouting pressure of the subsequent tunnel must be reduced, the circumferential and radial spacing of the grouting holes in the subsequent tunnel is encrypted to 0.8 m.

[0012] Furthermore, the grouting hole layout includes the setting of the grouting hole angle. In the grouting stage of the advanced tunnel, a large angle is used to inject into the rock mass between the tunnels to carry out full-coverage pre-reinforcement of the strata between the tunnels; for the grouting of the subsequent tunnel, a relatively vertical angle is used for injection, and only the soil on the extension line of the tunnel needs to be treated for water-stop reinforcement.

[0013] Furthermore, there are three types of grouting slurries in the step (3), namely liquid A (sodium silicate), liquid B (phosphoric acid), and C (cement slurry). Liquid A is successively mixed with liquid B and liquid C through the slurry mixer at the end of the double tube to fully mix and synthesize AB liquid (sodium silicate and phosphoric acid mixture) and AC liquid (sodium silicate and cement slurry mixture) respectively.

[0014] Furthermore, the cement selected is PO42.5 ordinary Portland cement. The cement slurry is 1:1 cement slurry. The concentration of sodium silicate is 37 Baumé. The volume ratio of sodium silicate to phosphoric acid is 50:1. The volume ratio of cement slurry to sodium silicate is 1:0.5 - 1:1. The setting time is adjusted according to the on-site needs by adjusting the ratio of AB and AC liquids.

[0015] Furthermore, the estimation formula for the grouting volume in the step (3) is carried out according to the following formula: Q = Anα(1 + β); where: Q ---- total grouting volume, m 3 ; A ---- grouting range volume, m 3; n ---- The porosity of silty clay is taken as 40.4%, and the porosity of old loess is taken as 41.7%; α ---- The slurry filling coefficient (0.8); β ---- The loss coefficient of grouting material (0.1 - 0.3), taking 0.1; After calculation, the theoretical filling rate is 0.37.

[0016] Further, in the step (3), the grouting pressure: P = KH, where: P - the designed grouting pressure (final pressure value) (Mpa), H - the depth of the grouting location (m). K - the pressure coefficient determined by the grouting depth.

[0017] Further, the face plugging adopts I20 steel I-beams with a transverse spacing of 1.0 m, double-layer φ8 steel bar meshes are hung, the steel I-beams are connected by C22 connecting bars with a spacing of 1.0 m, and 30 cm thick C25 concrete is sprayed for closing.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention combines indoor geotechnical tests, on-site grouting tests and numerical simulation results, compares the excavation sequences of each pilot tunnel, the step distance between pilot tunnels, the excavation cycle length, etc. of the mined tunnel, optimizes the construction parameters such as the grouting pressure, the spacing of grouting holes, the incident angle of grouting holes, the grouting sequence, etc. of the left and right lines of the tunnel, formulates a grouting reinforcement and rapid excavation construction plan for the small clear distance mined tunnel in the high water level area, and ensures the stability of the face and the soil mass in the arch part during tunnel excavation. During the on-site mined tunneling process, the construction parameters are adjusted in a timely manner according to the intelligent monitoring data, and at the same time, measures such as reducing the spacing of steel grids, changing the temporary inverted arch grids to steel profiles, and appropriately expanding the excavation contour are implemented according to the on-site ground settlement and the deformation of the prior tunnel, improving the stiffness of the tunnel support structure, reducing the deformation influence of grouting on the tunnel gap stratum and the adjacent tunnel, ensuring the stability of the face and the soil mass in the arch part during tunnel excavation, and thus efficiently, accurately and safely completing the tunnel grouting and excavation construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic plan view of the grouting hole layout of the present invention.

[0020] Figure 2 It is a schematic longitudinal sectional view of the grouting hole layout of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] In order to make the implementation means, creative features, achieved purposes and effects of the present invention easy to understand, the present invention will be further described below with reference to specific drawings. In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "installation", "connection", "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection. It can be a mechanical connection or an electrical connection. It can be directly connected, or indirectly connected through an intermediate medium, and can be the internal communication of two components.

[0022] As Figure 1 , Figure 2 shown, a construction method for grouting reinforcement and rapid excavation of a small clear - distance tunnel in a high - water - level area includes the following steps:

[0023] Step (1). The interval tunnel is excavated by the "CRD" method, and the soil is excavated by the bench method in each pilot tunnel.

[0024] Step (2). After the entire heading face is excavated to the grout - stopping wall, the heading face is promptly sealed.

[0025] Step (3). The grouting is tentatively set as one cycle every 20m along the tunnel driving direction to form a 3m water - stopping disk. The full - section grouting is carried out in the order of first outside and then inside, and grouting holes are skipped at intervals, using the backward grouting process. After the next cycle of grouting is completed;

[0026] Step (4). Adjust the grouting length in a timely manner according to the actual grouting effect on - site. During the grouting process, strengthen the observation at the heading face, and prepare a certain amount of emergency rescue materials. Strengthen the monitoring of the ground surface and buildings during the grouting process to ensure the safety of the underground excavation construction and the ground buildings.

[0027] In the said step (3), it includes the layout of grouting holes. Before grouting, it is necessary to first carry out the work of surveying and setting out lines, draw the area to be reinforced, mark the specific position of each hole according to the grouting design drawing, and mark it with red paint.

[0028] The layout of the grouting holes includes the setting of the grouting hole spacing. The grouting reinforcement range is 2.0m outside the primary support contour line of the tunnel. The diameter of the grouting hole is Φ42mm. The circumferential and radial spacing of the grouting holes in the advanced tunnel is 1.0 - 1.5m. Considering that the grouting pressure of the subsequent tunnel must be reduced, the circumferential and radial spacing of the grouting holes in the subsequent tunnel is encrypted to 0.8m.

[0029] The layout of the grouting holes includes the setting of the grouting hole angle. In the grouting stage of the advanced tunnel, a large - angle incidence is used to the rock mass between the tunnels to carry out full - coverage pre - reinforcement of the strata between the tunnels; for the grouting of the subsequent tunnel, a relatively vertical angle of incidence is used, and only the soil on the extension line of the tunnel needs to be treated for water - stopping reinforcement.

[0030] There are three kinds of grouting slurries in the said step (3), namely liquid A (sodium silicate), liquid B (phosphoric acid), and C (cement slurry). Liquid A is successively and fully mixed with liquid B and liquid C through the slurry mixer at the end of the double - pipe to respectively synthesize AB liquid (sodium silicate and phosphoric acid mixed liquid) and AC liquid (sodium silicate and cement slurry mixed liquid).

[0031] The cement selected is PO42.5 ordinary Portland cement. The cement slurry is 1:1 cement slurry. The concentration of sodium silicate is 37 Baume degrees. The volume ratio of sodium silicate to phosphoric acid is 50:1. The volume ratio of cement slurry to sodium silicate is 1:0.5 to 1:1. The setting time is adjusted according to the on-site needs by adjusting the ratio of liquid AB and liquid AC.

[0032] The double-fluid grouting method is adopted for the material ratio, and the specific material ratio is based on the following ratio scheme; this mixing ratio is applicable to soft cohesive soil layers, and the setting time is more than 60s.

[0033]

[0034]

[0035] Note: Liquid A: Liquid B = 1:1 (volume ratio). The above is the mixing ratio of the two mixed liquids in unit volume. This mixing ratio should be adjusted according to the actual test results on-site to meet the design requirements.

[0036] The estimation formula for the grouting volume in step (3) is as follows: Q = Anα(1 + β)

[0037] In the formula: Q ---- total grouting volume, m 3 ; A ---- grouting range volume, m 3 ; n ---- for silty clay, the porosity is taken as 40.4%, and for old loess, the porosity is taken as 41.7%; α ---- slurry filling coefficient (0.8); β ---- grouting material loss coefficient (0.1 - 0.3), take 0.1; after calculation, the theoretical filling rate is 0.37.

[0038] The grouting pressure in step (3): P = KH, where: P ---- design grouting pressure (final pressure value) (Mpa), H ---- depth of the grouting location (m). K ---- pressure coefficient determined by the grouting depth.

[0039] The value of the pressure coefficient K:

[0040]

[0041] According to the formation permeability and the amount of slurry injected, the grouting pressure is generally selected as 0.5 - 1 Mpa.

[0042] The face plugging adopts I20 steel I-beams with a transverse spacing of 1.0 m, double-layer φ8 steel bar meshes are hung, the steel I-beams are connected by C22 connecting bars with a spacing of 1.0 m, and 30 cm thick C25 concrete is sprayed for sealing.

[0043] Construction monitoring of the mined-out section

[0044] Purpose of monitoring and measurement

[0045] Monitoring and measurement to ensure tunnel stability are important components of construction. By monitoring, the dynamics of surrounding rock, support structures, the ground surface and buildings are grasped, timely prediction and feedback are carried out, and the design is adjusted with the results and construction is guided.

[0046] (1) Monitor the stress and deformation of the surrounding rock, verify the design effect of the support lining, and ensure the stability of the surrounding rock and construction safety.

[0047] (2) Through the analysis and processing of measurement data, master the changing laws of stratum stability, foresee accidents and dangers, use it as the basis for adjusting and modifying the support design and construction methods, and provide information on the ultimate stability of the soil layer and support lining.

[0048] (3) Accumulate measurement data to provide a basis for engineering analogy for future underground building design and construction.

[0049] Principles for Layout of Measuring Points

[0050] (1) The determination of the type and quantity of observation points is comprehensively considered in combination with factors such as the nature of this project, geological conditions, design requirements, construction characteristics, etc., and can comprehensively reflect the working state of the monitored object;

[0051] (2) The measuring points set to verify the design data are arranged at the most unfavorable positions and cross-sections in the design, and the measuring points set in combination with construction are arranged at the first constructed parts under the same working conditions to timely feedback information and guide construction;

[0052] (3) The positions of the surface deformation measuring points should not only consider reflecting the deformation characteristics of the monitored object, but also be convenient for observing with instruments, and also be conducive to the protection of the measuring points;

[0053] (4) The embedded measuring points cannot affect or hinder the normal stress of the structure, and cannot weaken the stiffness and strength of the structure;

[0054] (5) When the measuring points are damaged during the construction process, measuring points should be supplemented as soon as possible at the original position or as close as possible to the original position to ensure the continuity of the observation data of this point;

[0055] (6) The surface measuring points are arranged corresponding to the crown and convergence measuring points; the in-tunnel convergence and crown settlement measuring points should be arranged as close as possible to the excavation face, and the initial readings should be recorded within 24 hours after excavation.

[0056] Monitoring and measurement during the concealed excavation of tunnels are a crucial part in ensuring the safety of tunnel construction. By monitoring the changes in data, the stress and deformation of surrounding rocks can be grasped at all times, ensuring the stability of tunnel surrounding rocks, facilitating the judgment of the effectiveness of the support structure, providing reference for the adjustment of support parameters and the application time of the secondary lining, and the monitoring data can provide certain reference for the tunnel design and construction under similar hydrogeological conditions in the future. During the concealed excavation of tunnels, the layout of monitoring item points shall be carried out strictly in accordance with the design drawings, and the monitoring contents include: in-tunnel observation and on-site surrounding inspection, crown settlement monitoring of tunnel surrounding rocks, tunnel clearance convergence monitoring, ground settlement monitoring, vertical displacement monitoring of the floor, etc.

[0057] The above has shown and described the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of the present invention claimed is defined by the appended claims and their equivalents.

Claims

1. A grouting reinforcement and rapid excavation construction method for small clear - distance tunnels in high - water - level areas, characterized in that: It includes the following steps: Step (1). The interval tunnel is excavated by the "CRD" method, and the earthwork is excavated by the bench method in each pilot tunnel. Step (2). After the entire heading face is excavated to the grout stop wall, the heading face shall be sealed in time. Step (3). The grouting is tentatively set as one cycle every 20 m along the tunnel driving direction to form a 3-m water stop disk. The full-section grouting is carried out in the order of first outside then inside and interval skip-hole grouting, adopting the backward grouting process. After the next cycle of grouting is completed; Step (4). Adjust the grouting length in time according to the actual grouting effect on site. During the grouting process, strengthen the observation of the heading face, and prepare a certain amount of emergency rescue materials. Strengthen the monitoring of the ground surface and buildings during the grouting process to ensure the safety of the underground excavation construction and the ground buildings.

2. The grouting reinforcement and rapid excavation construction method for small clear distance tunnels in high water level areas according to claim 1, characterized in that: The grouting hole layout is included in Step (3). Before grouting, it is necessary to first carry out the work of surveying and setting out, outline the area to be reinforced, mark the specific position of each hole according to the grouting design drawing, and mark it with red paint.

3. A grouting reinforcement and rapid excavation construction method for small clear distance tunnels in high water level areas according to claim 1, characterized in that: The grouting hole layout includes the setting of the grouting hole spacing. The grouting reinforcement range is 2.0 m outside the initial support contour line of the tunnel. The diameter of the grouting hole is Φ42 mm. The circumferential and radial spacing of the grouting holes in the advanced tunnel is 1.0 - 1.5 m. Considering that the grouting pressure of the subsequent tunnel must be reduced, the circumferential and radial spacing of the grouting holes in the subsequent tunnel is encrypted to 0.8 m.

4. A grouting reinforcement and rapid excavation construction method for small clear distance tunnels in high water level areas according to claim 1, characterized in that: The grouting hole layout includes the setting of the grouting hole angle. In the grouting stage of the advanced tunnel, a large angle is used to inject into the rock mass between the tunnels to conduct full-coverage pre-reinforcement of the strata between the tunnels; for the grouting of the subsequent tunnel, a relatively vertical angle is used for injection, and only the water-stop reinforcement treatment of the soil mass on the extension line of the tunnel is required.

5. A grouting reinforcement and rapid excavation construction method for small clear - distance tunnels in high - water - level areas according to claim 1, characterized in that: There are three types of grouting slurries in Step (3), namely liquid A (sodium silicate), liquid B (phosphoric acid), and C (cement slurry). Liquid A is fully mixed with liquid B and liquid C respectively through the slurry mixer at the end of the double tube to synthesize AB liquid (sodium silicate and phosphoric acid mixture) and AC liquid (sodium silicate and cement slurry mixture).

6. The grouting reinforcement and rapid excavation construction method for a small clear distance tunnel in a high water level area according to claim 5, characterized in that: The cement selected is PO42.5 ordinary Portland cement. The cement slurry is 1:1 cement slurry. The concentration of sodium silicate is 37 Baume degrees. The volume ratio of sodium silicate to phosphoric acid is 50:

1. The volume ratio of cement slurry to sodium silicate is 1:0.5 - 1:

1. The setting time is adjusted according to the on-site needs by adjusting the ratio of AB and AC liquids.

7. A grouting reinforcement and rapid excavation construction method for small clear - distance tunnels in high - water - level areas according to claim 1, characterized in that: In the step (3), the estimation formula for the grouting volume is as follows: Q = Anα(1 + β); where: Q ---- total grouting volume, m 3 ; A ---- volume of the grouting range, m 3 ; n ---- for silty clay, the porosity is taken as 40.4%, and for old loess, the porosity is 41.7%; α ---- slurry filling coefficient (0.8); β ---- grouting material loss coefficient (0.1 - 0.3), take 0.1; after calculation, the theoretical filling rate is 0.

37.

8. A grouting reinforcement and rapid excavation construction method for small clear - distance tunnels in high - water - level areas according to claim 1, characterized in that: The grouting pressure in Step (3): P = KH, where: P - the designed grouting pressure (final pressure value) (Mpa), H - the depth of the grouting location (m); K - the pressure coefficient determined by the grouting depth.

9. A grouting reinforcement and rapid excavation construction method for small clear distance tunnels in high water level areas according to claim 1, characterized in that: The heading face is sealed with I20 steel beams, with a transverse spacing of 1.0 m, double-layer φ8 steel bar meshes are hung, the steel beams are connected with C22 connecting bars, with a spacing of 1.0 m, and 30-cm-thick C25 concrete is sprayed for sealing.

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