A construction method for receiving underwater exit of a shield tunnel with a small radius and large slope and ultra-shallow buried

Abstract

The invention relates to a construction method for receiving an underwater exit tunnel of an ultra-shallow buried shield with a small radius and a large slope, which comprises the following steps: reinforcing the end of a receiving well; applying counterweight back pressure to the top of the tunnel, applying back pressure to the receiving site using concrete supports; casting plain walls in a tunnel gate circle and constructing water-soil retaining walls; casting a receiving mortar base in the receiving well; backfilling the receiving well with mud; when the shield enters the receiving range, controlling the excavation of the shield arrival section; when the shield machine excavates into the water tunnel of the receiving well, blocking the tunnel gate circle; after the shield machine excavates to the stop position, the annular pipe segments of the tunnel opening are connected and tightened by a tensioning device when the shield receives, mud and water are cleaned in the receiving well, and then the tunnel gate and the shield tail of the shield are fixed together by an arc steel plate. The method overcomes the engineering difficulties such as the shallow buried depth of the shield receiving section, the large pressure head, the small curve radius, the large slope, and the upper soft and lower hard strata, and ensures the safety of the shield receiving process.

Description

Technical Field

[0001] The invention relates to the technical field of tunnel construction, and in particular to an underwater exit and receiving construction method for an ultra-shallow buried shield machine with a small radius and a large slope. Background Art

[0002] Shield route design often faces some complex situations. For example, when the shield tunnel has the characteristics of small radius, large slope, and ultra-shallow burial, the difficulty of shield starting and receiving is significantly increased. In addition, when building subway tunnels, the route may pass through soft upper and hard lower strata, and often passes under surface roads, railways, water, gas and electricity pipelines, further increasing the difficulty of shield receiving.

[0003] For tunnels with a small radius, it will make it difficult to control the posture of the shield machine and the assembly of the segments; for tunnels with a large slope, when the shield machine receives and exits the tunnel, its top is very close to the shield shaft structural beam. If the shield machine exits the tunnel with a large slope, it is easy to hit the shield shaft structural beam; when the shield receiving end is shallow, if the excavation posture and synchronous grouting are not controlled well, the shield machine head is likely to lift up or sink, and the ground surface will experience excessive settlement or uplift; in the process of receiving soft upper and hard lower strata, the shield machine cuts the soil above and the rock surface below, which will cause uneven force on the shield machine face and easily deviate from the predetermined axis.

[0004] The launching and receiving of shield tunnels greatly disturb the ground surface, causing large structural cracks in surface buildings and even overturning. In order to reduce surface settlement and soil displacement, when the working space of the shield shaft is small, the shield receiving shaft is often filled with water or mud. When the receiving part of the shield is located in the railway section, if the steel sleeve is used, the steel sleeve hoisting operation needs to be reported to the relevant departments, which is cumbersome, delays the construction period, has high rental costs, is inconvenient to transport, and the total cost is significantly higher than the underwater receiving method. Summary of the invention

[0005] The purpose of the present invention is to provide a construction method for receiving underwater exit of a shield machine with a large radius and an ultra-shallow burial. The method can be used for receiving underwater exit of a shield machine with a small radius, a large slope and an ultra-shallow burial under specific working conditions, overcome the engineering difficulties such as the shallow burial depth of the receiving section of the shield machine, a large pressure head, a small curve radius, a large slope, and being located in a soft upper and hard lower stratum, and ensure the safety of the shield machine receiving process.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] A construction method for receiving an underwater exit hole of an ultra-shallow shield with a small radius and a large slope, characterized in that the construction method for receiving an underwater exit hole of an ultra-shallow shield with a small radius and a large slope comprises the following steps:

[0008] Step 1: Reinforce the end of the receiving well;

[0009] Step 2: counterweight the tunnel and use concrete support to counterpressure the receiving area;

[0010] Step 3: Cast the plain wall and water-soil retaining wall inside the tunnel gate circle;

[0011] Step 4: pouring a receiving mortar base in the receiving well;

[0012] Step 5: Backfill the receiving well with mud;

[0013] Step 6: When the shield enters the receiving range, control the excavation of the shield arrival section;

[0014] Step 7: When the shield machine excavates into the water tunnel of the receiving well, the tunnel door ring is sealed;

[0015] Step 8: When the shield machine excavates to the stop position, the ring segments at the tunnel opening are connected and tightened with a tensioning device when the shield receives, the receiving well is cleaned of mud and water, and then the tunnel door and the shield tail of the shield are fixed together with an arc steel plate;

[0016] Step 9. After the above work is completed, the shield will be lifted and dismantled.

[0017] The present invention also comprises the steps of:

[0018] In the step 1, triple-tube jet grouting piles are used as the end reinforcement of the shield receiving well, emergency dewatering wells are set up inside and outside the soil reinforcement area, and emergency dewatering is started in time according to actual conditions. The jet grouting piles are constructed by interval skipping method, and the construction time interval between two adjacent piles is not less than 48 hours.

[0019] In the step one, the construction sequence of the reinforcement body is arranged according to the site conditions, the grouting pile caulking construction is carried out after the main structure of the station is completed, and after the double-tube grouting pile construction is completed, before the reinforcement construction is completed and the shield is started to receive it, the reinforcement effect is tested to ensure that the reinforcement effect meets the requirements of the tunnel construction, and longitudinal horizontal exploration holes with a length not exceeding the reinforcement body range are drilled within the plane range of the tunnel portal, with a number of no less than 9 holes for each tunnel portal range. The quality of the reinforcement body is checked by observing the water seepage of the exploration holes. If water seepage is found, grouting construction measures should be taken immediately to cut off the water seepage channel.

[0020] In the step 2, back pressure is applied to the receiving site using concrete support;

[0021] The counter-pressure counterweight measures are as follows: using steel plates and steel ingots for counterweight inside the shield, on the walking beam of the assembly machine, and at the position of the 2 to 9 ring segments behind the shield tail, and installing a counterweight trolley at the front section of the equipment bridge to increase the deadweight of the segments after they are out of the shield tail;

[0022] In the step 3, after the tunnel portal re-survey is completed, before the shield machine reaches the shield receiving shaft, a plain concrete retaining wall is cast at the tunnel portal, and before the water and soil backfilling, a reinforced concrete blocking wall is cast on the other side of the shield receiving shaft, and the shield cutter cutting area is overlapped with glass fiber reinforcement and ordinary reinforcement;

[0023] The side wall of the receiving shaft is the structural wall of the double shield receiving working shaft, which is cast using a combination of C35 reinforced concrete + frame columns and will not be demolished subsequently.

[0024] In the step 4, the mortar base is poured from the bottom plate to 0.2m above the lower edge of the tunnel portal steel ring to ensure that the mortar base can be cut to form effective support when the shield exits the tunnel.

[0025] In the step 5, after the end of the shield receiving shaft has been fully reinforced, the tunnel retaining wall, the water and soil sealing wall, and the mortar base have been cast and the strength meets the requirements, the mud backfilling operation begins;

[0026] Pour mud made from soil and water transported from the shield machine at the construction site into the shield receiving shaft. Pour the mud until the height reaches the bottom of the structural beam of the shield receiving shaft;

[0027] During the backfilling operation, the earth required for filling must be silty clay or silty clay, and sand must not be used; and the earth must not contain garbage such as stones with a diameter greater than 2 cm; during the backfilling process, a grab machine or a telescopic arm excavator is used to grab the earth and lower it to about 3 meters from the bottom of the working pit to avoid damage to the retaining wall and the tunnel door due to the free fall impact during the backfilling process.

[0028] In step 6, when the shield enters the receiving range, the shield machine penetration posture is corrected according to the designed central axis of the tunnel. The correction should be completed step by step, and the correction of one ring should not exceed 4mm;

[0029] During the first 50 to 100 rings of the shield machine entering the tunnel, each control point is rechecked and measured, and the center line of the tunnel entrance portal is measured and rechecked. The shield machine's posture is adjusted according to the measurement results. During the last 50 rings of advancement, the shield axis is corrected multiple times. The correction principle is "small amounts and multiple times" to control the shield machine's posture within ±15mm horizontally and +20 to +30mm vertically. The shield axis angle change caused by the deviation of the shield plane and elevation is controlled to not exceed 0.4%, ensuring the accuracy of the axis and ensuring the safe entry of the shield machine into the portal circle.

[0030] In the step 7, when the shield machine excavates into the water tunnel, the tunnel gate is sealed with grouting, and the double liquid slurry is injected in the last 10 rings of the tunnel entry section to prevent the pipe segments from sinking and misalignment; the injection position is the third ring position after the shield tail is dragged out; the double liquid slurry is divided into liquid A and liquid B, the material of liquid A is cement slurry or cement mortar, and liquid B is water glass;

[0031] The plugging grouting process is specifically as follows:

[0032] When the shield reaches the designated mileage, it stops excavating and performs secondary supplementary grouting on the four ring segments near the tunnel entrance to seal the tunnel entrance. The secondary grouting uses cement-water glass double liquid slurry as the grouting material, and the slurry ratio is 1:1:1. The secondary reinforcement grouting uses a self-provided double liquid grouting pump. The secondary grouting pressure is 0.3-0.5Mpa, and the grouting volume of a single hole is controlled at 0.8-1m 3 The single ring grouting volume is not more than 6m 3 In general, reinforcement grouting is controlled by pressure, and the grouting holes in the pipe segments are opened to check for water leakage behind the wall to determine the end of grouting.

[0033] In the step eight, after the shield machine excavates to the parking position, in order to prevent the gap between the pipe segments from increasing after the jacking force is released, causing the ring gap to leak, the 1-10 rings of the pipe segments at the tunnel opening are connected and tightened with a tensioning device when the shield machine receives the pipe segments;

[0034] After the tensioning device is installed, water and soil cleaning work is carried out. Pumping water and clearing mud requires the cooperation of 3 high-power water pumps and grab buckets. When the water level in the shield receiving well is pumped to a certain level, the earth on the top of the shield machine is grabbed to the ground with a grab bucket. The soil around the shield machine is manually excavated. When clearing mud, the slope is cleared. First, the soil at the tunnel entrance is cleared to ensure the timely welding of the arc steel plate and the shield tail;

[0035] As the mud and water are being cleaned, arc-shaped steel plates are used to weld the steel plates at the end of the tunnel ring with the steel plates of the shield tail shell to form an effective seal. Six grouting ball valves are pre-installed on the ring plate of the tunnel ring and evenly arranged along the tunnel ring. After welding, the six ball valves are used to grout the tunnel. The tunnel is completely sealed, and the shield machine is dismantled and hoisted out. After thawing, holes are opened on the pipe segments to check the grouting sealing. If the grouting is not dense, continue to add double liquid slurry until multiple holes are opened to check for water leakage.

[0036] Compared with the existing technology, the beneficial effects of the present invention are embodied in: the technical method disclosed in the patent can effectively solve the construction problems under small radius, large slope and ultra-shallow burial conditions; the new shield underwater receiving method adopted is suitable for railway sections, and the cost is significantly lower than conventional receiving or steel sleeve receiving; the use of counter-pressure counterweights to perform counter-pressure on the top of the tunnel, and the use of concrete supports to perform counter-pressure within the receiving site can effectively prevent the shield head from floating up, and can effectively reduce the settlement or uplift of the surrounding surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is the plan view of the shield receiving shaft.

[0038] Figure 2 This is a side section view of the shield receiving shaft.

[0039] Figure 3 Reinforcement plan for the receiving end of the shield machine.

[0040] Figure 4 This is the structural diagram of the shield machine entering and exiting the tunnel.

[0041] Figure 5 Side cutaway view of the receiving end plugging arrangement.

[0042] In the figure: 1. Portal retaining wall; 2. Receiving shaft side wall; 3. Water and soil sealing wall; 4. Shield tunnel; 5. Shield receiving shaft; 6. Shield lifting hole; 7. Shield shaft structure beam; 8. Mortar base; 9. Portal ring; 10. Retaining structure; 11. Soil reinforcement area; 12. Shield tail; 13. Arc steel plate; 14. Mud; 15. Dewatering well; 16. Jet jet piles. DETAILED DESCRIPTION

[0043] Combination Figures 1 to 5 As shown, the present invention is further described:

[0044] In order to overcome the technical defects of the prior art underwater receiving method of shield, which has a large disturbance amplitude on the surface under small radius, large slope and ultra-shallow burial conditions, the present invention provides a new underwater receiving method of shield, which can effectively overcome the engineering difficulties such as shallow burial depth of the shield receiving section, large pressure head, small curve radius, large slope, and being located in soft upper and hard lower strata, thereby ensuring the safety of the shield receiving process.

[0045] The novel shield underwater receiving method described in the present invention comprises the following steps: soil reinforcement at the receiving end → tunnel circle layout → plain wall casting in the tunnel gate circle and water-soil retaining wall construction → mortar casting for the base → horizontal exploration hole → acceptance of arrival conditions → removal of tunnel gate concrete → backfilling of water and soil in the well and arrival of the shield → grouting and filling of the tunnel entrance section → cleaning and excavation in the well → arc steel plate welding of the tunnel ring for sealing.

[0046] The specific steps include:

[0047] Step 1: Reinforcement of the receiving well head

[0048] Triple-tube jet grouting piles 16 are used as the end reinforcement of the shield receiving shaft 5. At the same time, emergency dewatering wells 15 are set inside and outside the soil reinforcement area 11, and emergency dewatering is started in time according to the actual situation. The jet grouting pile construction adopts the method of 1, 3, 2, 5, 4, 7..., and the construction time interval between two adjacent piles should be no less than 48 hours.

[0049] The construction sequence of the reinforcement body is arranged according to the site conditions, but the caulking construction of the triple-tube rotary jet pile 16 must be carried out after the completion of the main structure of the station and after the construction of the double-tube rotary jet pile 16 is completed. Before the reinforcement construction is completed and the shield is started to receive, the reinforcement effect should be tested to ensure that the reinforcement effect meets the requirements for tunnel construction. Longitudinal horizontal exploration holes with a length not exceeding the range of the reinforcement body are drilled within the plane range of the tunnel portal, and the number of holes for each tunnel portal is not less than 9. The quality of the reinforcement body is checked by observing the water seepage of the exploration holes. If water seepage is found, grouting construction measures should be taken immediately to cut off the water seepage channel.

[0050] In the specific example, the receiving end is reinforced with φ800@600 / 500 triple-tube jet-jet piles 16 outside the retaining structure 10, and a row of φ800@500 triple-tube jet-jet piles 16 is used for reinforcement on the outside of the retaining structure 10 (800mm thick interlocking piles), with a reinforcement length of 1m below the shield tunnel portal; φ800@600 triple-tube jet-jet piles 16 are used for reinforcement on the outside of the first row, overlapping the first row by 300mm, and the reinforcement length is from the ground to the rock surface. The reinforcement range of the receiving end is: longitudinally 3m outside the retaining structure 10 in the tunnel direction, and horizontally 3m outside the tunnel portal structure.

[0051] Step 2: Set the counter-pressure weight.

[0052] Counterweight is applied to the top of the tunnel, and concrete support is used to apply counter pressure within the receiving site.

[0053] The counter-pressure counterweight measures are as follows: using steel plates and steel ingots for counterweight inside the shield, on the walking beam of the assembly machine, and at the position of the 2 to 9 ring segments behind the shield tail, and installing a counterweight trolley at the front section of the equipment bridge to increase the deadweight of the segments after they are out of the shield tail;

[0054] Step 3: Casting of plain walls and construction of water and soil retaining walls within the tunnel gate circle.

[0055] After the portal resurvey is completed, before the shield machine reaches the shield receiving shaft 5, a plain concrete retaining wall 1 is cast at the portal, and before backfilling with soil and water, a reinforced concrete blocking wall 3 is cast on the other side of the shield receiving shaft 5. Glass fiber reinforcement and ordinary steel bars are overlapped in the shield cutter cutting area.

[0056] The receiving shaft side wall 2 described in this patent is the structural wall of the double shield receiving working shaft, which is cast using a combination of C35 reinforced concrete + frame columns and will not be demolished later.

[0057] In the specific example, a 30cm portal retaining wall 1 is cast with C35 concrete within the portal range, and the reinforced concrete blocking wall 3 set on the other side of the shield receiving shaft 5 is made of C35 concrete. The vertical steel bars are φ25@150 close to the portal side and φ22@150 on the other side. The horizontal bars are φ20@150, and the hooks are made of φ10 round steel, arranged in a plum blossom shape.

[0058] Step 4: Pour the receiving mortar base.

[0059] The mortar base 8 is poured from the bottom plate to about 0.2m above the lower edge of the tunnel gate steel ring to ensure that the mortar base 8 can be cut to form an effective support when the shield machine exits the tunnel. First, the center line of the receiving base is determined according to the design axis line of the shield machine here, and the shield machine adopts a straight line receiving method. The mortar mix ratio is determined before pouring, and the receiving mortar base 8 should meet the strength requirements before the shield machine enters the shield receiving shaft 5.

[0060] In the specific example, an M5 base mortar foundation 8 is provided, with dimensions of 15x5x1.5m, and the foundation is cast from the bottom plate to about 0.5m above the lower edge of the portal steel ring.

[0061] Step 5: Mud backfill.

[0062] After the end of the shield receiving shaft 5 has been fully reinforced, the tunnel retaining wall 1, the water and soil sealing wall 2, and the mortar base 8 have been cast and the strength meets the requirements, the mud backfilling operation begins. The mud 14 made of the slag transported by the shield machine at the construction site and mixed with water is poured into the shield receiving shaft 5. The mud 14 is poured until the height reaches the bottom of the structural beam 7 of the shield receiving shaft 5.

[0063] The following points should be noted for the backfilling operation: (1) The earthwork required for backfilling must be silty clay or silty clay. Sand must not be used. In addition, the earthwork must not contain stones or other garbage with a diameter greater than 2 cm. (2) During the backfilling process, a grabber or telescopic excavator should be used to grab the earthwork and place it about 3 meters from the bottom of the working pit to avoid damage to the retaining wall and the tunnel door due to the free fall impact during the backfilling process.

[0064] When the shield machine enters the receiving range, the shield machine's penetration posture correction is carried out according to the tunnel design central axis. The correction should be completed step by step, and the correction of one ring should not exceed 4mm.

[0065] 50 to 100 rings before the shield machine enters the tunnel, each control point is rechecked and measured, and the center line of the tunnel entrance is measured and rechecked at the same time. The shield machine posture is adjusted according to the measurement results. During the last 50 rings of advancement, the shield axis is corrected multiple times. The correction principle is "small amount and multiple times" to control the shield machine posture within ±15mm in the horizontal direction and +20 to +30mm in the vertical direction. The shield axis angle change caused by the deviation of the shield plane and elevation is controlled not to exceed 0.4%, ensuring the accuracy of the axis and ensuring the safe entry of the shield machine into the tunnel entrance circle 9.

[0066] The following points should be noted when controlling the excavation of the receiving section of the shield machine: (1) before the shield machine enters the tunnel, an earth pressure gauge is installed on the retaining wall to observe the impact of the shield machine's advancement on the retaining wall. When the alarm value is reached, the advancement is stopped; (2) during the advancement of the shield machine, the screw machine is used to carry out appropriate excavation to avoid excessive excavation that causes the fill to sink. (3) During the excavation process, maintain low speed and low thrust to avoid soil erosion caused by backfill in the water tunnel due to excessive excavation, and reduce the impact on the interface between the cutter and the rock and soil to maintain the stability of the shield posture; (4) Before the shield is received, check whether the soil reinforcement and water blocking conditions of the end well meet the requirements; (5) Increase the frequency of surface settlement monitoring and adjust the shield posture in time according to the settlement monitoring results; (6) Use the over-excavation cutter to over-excavate the lower rock layer, and use the articulated jack to control the axis of the shield machine. The allowable deviation of the axis of the shield machine is controlled within ±50mm in the plane and ±50mm in the elevation; (7) Ensure the sealing of the shield tail while grouting, and do not allow the slurry to leak out from between the shield machine and the pipe segment; (8) According to the size of the tool rolling angle, adjust the cutter head direction (left or right) in time to prevent the shield body from twisting; (9) Control the propulsion oil pressure of the upper and lower jacks to maintain the correct excavation route; (10) Use heavy rock breaking tools in soft upper and hard lower strata.

[0067] When double-line shield machines are entering tunnels under conditions of small spacing, large slopes, and ultra-shallow burials, if the minimum line spacing is less than the shield diameter, it is necessary to adopt the approach of excavating the first shield machine first and then the second tunnel. One shield machine will first excavate 100m and exit the tunnel at the end of shield receiving shaft 5, and the second shield machine will exit the tunnel later.

[0068] To prevent the tunnel segments from loosening, the segments at the locations with close spacing should be further reinforced. The last 10-15 rings of the shield tunnel segments should be longitudinally tightened by multi-point steel welding;

[0069] The segment tensioning device is longitudinally arranged within the small spacing range of the shield, and is fixed to the segment with bolts in 6 circumferential directions (one for each segment, at the same row of bolts). First, holes are drilled in the channel steel, and the holed channel steel is placed on the bolts, and then tightened with washers and nuts to prevent the segment from deformation.

[0070] For underwater reception of shield under conditions of small spacing, large slope and ultra-shallow burial, the stratum loss rate should be controlled to be ≤3‰, and the uneven settlement of nearby buildings should not exceed 1.5‰L (L is the center distance of adjacent column foundations); the uneven settlement of nearby bridge and culvert foundations should not exceed 2‰; the safety verification of the shield structure should consider the impact within 50m outside the outer edge of the shield structure.

[0071] In the specific example, the start time of shield receiving is defined as the entire construction process from 50m before the shield machine arrives at the next station receiving shaft to the shield machine passing through the shield tunnel 4 and entering the shield receiving shaft 5 and being pushed onto the shield receiving base. During the underwater receiving operation, the original operating speed of the surface railway is 105km / h, and the speed limit during construction is 45km / h.

[0072] In the specific example, the weight of the shield machine used is 574t, the maximum thrust is 4255T, the friction coefficient between steel and soil is 0.3, and the friction coefficient between wheels and rails is 0.15; for soil-rock combined strata, low speed and low penetration are maintained during excavation, the grouting pressure is controlled at 0.7-1.2bar, and the grouting volume per ring is controlled at 4.9m 3 For full-section rock formations, high rotation speed and low penetration rate are maintained during excavation, grouting pressure is controlled at 1-1.5 bar, and grouting volume per ring is controlled at more than 4.9 cubic meters.

[0073] In the specific example, the strata involved in shield tunnel 4 include silt, strongly weathered sandy mudstone, and moderately weathered sandy mudstone. The top of the receiving end shield is 3.6m away from the ground surface, the shield curve radius is 300m, the shield outer diameter is 6.2m, the inner diameter is 5.5m, the ring width is 1.2m, the excavation direction error is controlled not to exceed ±50mm, and the surface allowable uplift value is +10 / -30mm; the main structure of the shield is lined with prefabricated reinforced concrete segments. There are 6 segments in each ring. The segments are assembled with staggered joints, and the longitudinal joint contact surface is provided with tongue and groove, with a thickness of 0.35m and a width of 1.2m. The concrete is C50 impermeability grade P10, and the segments are connected with 8.8-grade M30 bent bolts. The width of the cracks in the segment concrete is controlled not to exceed 0.2mm.

[0074] In the specific example, the total thrust of the receiving end shield is controlled below 800T, the torque is controlled within 2000KN.m, the cutter head speed is controlled within 0.8~1r / min, the centerline deviation is controlled within ±2cm, the penetration is within 10mm / r, the foam content is 3% / 20-40L, and the bentonite content is 1:11 / 9~12m³ / ring. The excavation speed during the pile grinding process is controlled at 3-5mm / min, and the excavation speed through the receiving end soil reinforcement area 11 is controlled at 10~20mm / min.

[0075] In a specific example, the shield machine exits the tunnel at a large slope of 35‰. The segment tensioning device uses M36 bolts to fix the 14b channel steel to the segment. First, a 4cm hole is made in the 14b channel steel, and then the channel steel with the hole is put on the bolt and tightened with washers and nuts to prevent the segment from deformation.

[0076] Step 7: Sealing the tunnel door ring;

[0077] When the shield machine excavates into the water tunnel (when the shield tail has not separated from the pre-buried steel ring of the tunnel portal), the tunnel portal plugging grouting construction is carried out, and the double liquid slurry is injected in the last 10 rings of the tunnel entry section to prevent the pipe segments from sinking and misalignment. The injection position is the third ring position after the shield tail is dragged out. The double liquid slurry is divided into A liquid and B liquid. The material of A liquid is cement slurry or cement mortar, and B liquid is water glass.

[0078] In the specific example, the water-cement ratio of the two-liquid slurry used is 1:1, the volume ratio of liquid A to liquid B is 1:1, and the slurry density is set at 1.44 g / cm 3 , coagulation time 40~60s.

[0079] The plugging grouting process is specifically as follows:

[0080] When the shield reaches the designated mileage, it stops excavating and performs secondary supplementary grouting on the 4 rings (0-3 rings) of segments near the tunnel entrance to seal the tunnel entrance. The secondary grouting uses cement-water glass double liquid slurry as the grouting material, and the slurry ratio is 1:1:1. The secondary reinforcement grouting uses a self-provided double liquid grouting pump. The secondary grouting pressure is 0.3-0.5Mpa, and the grouting volume of a single hole is controlled at 0.8-1m 3 The single ring grouting volume is not more than 6m 3 In general, reinforcement grouting is controlled by pressure, and the grouting holes in the pipe segments are opened to check for water leakage behind the wall to determine the end of grouting.

[0081] In order to ensure the shield machine's safe entry into the tunnel, the soil at the tunnel entrance must have good self-sustainability and compactness. In order to ensure that the soil does not collapse and groundwater does not gush out when the shield machine enters the tunnel, and to complete the start smoothly, the tunnel gate must be blocked. After the +11 ring is installed, the excavation is stopped and the double liquid slurry is used to block the tunnel gate through the secondary grouting measures. When the +11 ring is advanced, 4m³ bentonite is injected into the shield tail through the synchronous grouting system to prevent the double liquid slurry from wrapping the shield tail. After the advancement is completed, the tunnel gate is blocked by secondary supplementary grouting of the 4 rings (0-3 rings) of the pipe segments near the tunnel gate. The leakage behind the wall is checked through the opening of the grouting hole of the pipe segment (open the ball valve above the steel sleeve) to determine the end of grouting.

[0082] Step 8: Mud and water cleaning, tensioning device, and arc steel plate welding.

[0083] After the shield machine excavates to the parking position, in order to prevent the gap between the segment rings from increasing due to the release of the jacking force, causing annular leakage, 1 to 10 rings of segments at the tunnel entrance are connected and tightened with a tensioning device when the shield machine is receiving it.

[0084] After the tensioning device is installed, water and soil cleaning work is carried out. Pumping water and clearing mud requires the cooperation of 3 high-power water pumps and grab buckets. When the water level in the shield receiving shaft 5 is pumped to a certain level, the earth on the top of the shield machine is grabbed to the ground by a grab bucket. The soil around the shield machine is manually excavated. When clearing mud, the slope is cleared. First, the soil at the tunnel entrance is cleared to ensure the timely welding of the arc steel plate 13 and the shield tail 12.

[0085] As the mud and water are being cleaned, the steel plate at the end of the tunnel ring 9 and the shell steel plate of the shield tail 12 are welded together using the curved steel plate 13 to form an effective seal. Six grouting ball valves are pre-installed on the ring plate of the tunnel ring 9 and are evenly arranged along the tunnel ring 9. After welding, the six ball valves are used to grout the tunnel. The tunnel is completely sealed, and the shield machine is dismantled and hoisted out. After thawing, holes are opened on the pipe segments to check the grouting sealing. If the grouting is not dense, continue to add double liquid slurry until multiple holes are opened to check for water leakage.

[0086] Step 9: Shield lifting and dismantling.

[0087] After the shield machine reaches the shield receiving shaft 5, it begins to be disassembled, and the components are lifted out from the shield lifting hole 6. According to the structural dimensions of each component of the shield machine and the actual conditions on site, the shield machine lifting and disassembly process is as follows:

[0088] Plan approval → Site condition acceptance → Shield machine arrives → Crane enters site for assembly → Shield machine dismantles → Cutterhead is hoisted out → Front and middle shields are separated → Middle shield is hoisted out → Front shield is hoisted out → Track laying → Rear trailer is hoisted out → Crane exits site → Site is restored → Dismantling is completed.

[0089] In the process described above, before the cutter disc is lifted out, the main engine lifting ears and the front and middle shield top moving brackets should be welded, and the pipelines should be removed.

[0090] The specific process of shield dismantling in the process is: push the cutter head out of the tunnel portal, remove the slewing center, weld the lifting lugs and inspect for flaws, tighten the wire rope connected to the cutter head with a crane after the lifting lugs are accepted, remove the cutter head connection bolts with special tools, and after the dismantling is completed, lift the cutter head out of the well with a crane.

[0091] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0092] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A small radius and large slope ultra-shallow buried shield underwater exit receiving construction method, characterized by: The steps include: Step 1: Reinforce the end of the receiving well; Step 2: counterweight the tunnel and use concrete support to counterpressure the receiving area; Step 3: Cast the plain wall and water-soil retaining wall inside the tunnel gate circle; Step 4: pouring a receiving mortar base in the receiving well; Step 5: Backfill the receiving well with mud; Step 6: When the shield enters the receiving range, control the excavation of the shield arrival section; Step 7: When the shield machine excavates into the water tunnel of the receiving well, the tunnel door ring is sealed; Step 8: When the shield machine excavates to the stop position, the ring segments at the tunnel opening are connected and tightened with a tensioning device when the shield receives, the receiving well is cleaned of mud and water, and then the tunnel door and the shield tail of the shield are fixed together with an arc steel plate; Step 9: After the above work is completed, the shield is hoisted and dismantled; Wherein, in the step 2, a concrete support is used to perform back pressure within the receiving site; The counter-pressure counterweight measures are as follows: using steel plates and steel ingots for counterweight inside the shield, on the walking beam of the assembly machine, and at the position of the 2 to 9 ring segments behind the shield tail, and installing a counterweight trolley at the front section of the equipment bridge to increase the deadweight of the segments after they are out of the shield tail; In the step 3, after the tunnel portal re-survey is completed, before the shield machine reaches the shield receiving shaft, a plain concrete retaining wall is cast at the tunnel portal, and before the water and soil backfilling, a reinforced concrete blocking wall is cast on the other side of the shield receiving shaft, and the shield cutter cutting area is overlapped with glass fiber reinforcement and ordinary reinforcement; The side wall of the receiving shaft is the structural wall of the double shield receiving working shaft, which is cast by a combination of C35 reinforced concrete + frame columns and will not be demolished later; In the step 5, after the end of the shield receiving shaft has been fully reinforced, the tunnel retaining wall, the water and soil sealing wall, and the mortar base have been cast and the strength meets the requirements, the mud backfilling operation begins; Pour slurry made of soil and water transported from the shield machine at the construction site into the shield receiving well; Pour the slurry until the height reaches the bottom of the structural beam of the shield receiving shaft; During the backfilling operation, the earth required for filling must be silty clay or silty clay, and sand must not be used; and the earth must not contain garbage such as stones with a diameter greater than 2 cm; during the backfilling process, a grab machine or a telescopic arm excavator is used to grab the earth and lower it to about 3 meters from the bottom of the working pit to avoid damage to the retaining wall and the tunnel door due to the free fall impact during the backfilling process.

2. The method for receiving underwater exit of an ultra-shallow shield with a small radius and a large slope according to claim 1 is characterized in that: In the step 1, triple-tube jet grouting piles are used as the end reinforcement of the shield receiving well, emergency dewatering wells are set up inside and outside the soil reinforcement area, and emergency dewatering is started in time according to actual conditions. The jet grouting piles are constructed by interval skipping method, and the construction time interval between two adjacent piles is not less than 48 hours.

3. The method for receiving underwater exit of an ultra-shallow shield with a small radius and large slope according to claim 2 is characterized in that: In the step one, the construction sequence of the reinforcement body is arranged according to the site conditions, the grouting pile caulking construction is carried out after the main structure of the station is completed, and after the double-tube grouting pile construction is completed, before the reinforcement construction is completed and the shield is started to receive it, the reinforcement effect is tested to ensure that the reinforcement effect meets the requirements of the tunnel construction, and longitudinal horizontal exploration holes with a length not exceeding the reinforcement body range are drilled within the plane range of the tunnel portal, with a number of no less than 9 holes for each tunnel portal range. The quality of the reinforcement body is checked by observing the water seepage of the exploration holes. If water seepage is found, grouting construction measures are taken to cut off the water seepage channel.

4. The method for underwater exit and receiving construction of a small-radius, large-slope ultra-shallow shield tunnel according to claim 1 is characterized in that: In the step 4, the mortar base is poured from the bottom plate to 0.2m above the lower edge of the tunnel portal steel ring to ensure that the mortar base can be cut to form effective support when the shield exits the tunnel.

5. The method for underwater exit and receiving construction of a small-radius, large-slope ultra-shallow shield tunnel according to claim 1 is characterized in that: In step 6, when the shield enters the receiving range, the shield machine penetration posture is corrected according to the designed central axis of the tunnel. The correction should be completed step by step, and the correction of one ring should not exceed 4mm; During the first 50 to 100 rings of the shield machine entering the tunnel, each control point is rechecked and measured, and the center line of the tunnel entrance portal is measured and rechecked. The shield machine's posture is adjusted according to the measurement results. During the last 50 rings of advancement, the shield axis is corrected multiple times to control the shield machine's posture within ±15mm in the horizontal direction and +20 to +30mm in the vertical direction. The shield axis angle change caused by the deviation of the shield plane and elevation is controlled to not exceed 0.4%, ensuring the accuracy of the axis and ensuring the safe entry of the shield machine into the portal circle.

6. The method for receiving underwater exit of an ultra-shallow shield with a small radius and a large slope according to claim 1 is characterized in that: In the step 7, when the shield machine excavates into the water tunnel, the tunnel gate is sealed with grouting, and the double liquid slurry is injected in the last 10 rings of the tunnel entry section to prevent the pipe segments from sinking and misalignment; the injection position is the third ring position after the shield tail is dragged out; the double liquid slurry is divided into liquid A and liquid B, the material of liquid A is cement slurry or cement mortar, and liquid B is water glass; The plugging grouting process is specifically as follows: When the shield reaches the designated mileage, it stops excavating and performs secondary supplementary grouting on the four ring segments near the tunnel entrance to seal the tunnel entrance. The secondary grouting uses cement and water glass double liquid slurry as the grouting material, and the slurry ratio is 1:1:

1. The secondary reinforcement grouting uses a self-provided double liquid grouting pump. The secondary grouting pressure is 0.3-0.5Mpa, and the grouting volume of a single hole is controlled at 0.8-1m 3 The single ring grouting volume is not more than 6m 3 The reinforcement grouting is controlled by pressure, and the leakage behind the wall is checked through the opening of the grouting holes in the pipe segment to determine the end of the grouting.

7. The method for underwater exit and receiving construction of a small radius and large slope ultra-shallow shield according to claim 1 is characterized in that: In the step eight, after the shield machine excavates to the parking position, in order to prevent the gap between the pipe segments from increasing after the jacking force is released, causing the ring gap to leak, the 1-10 rings of the pipe segments at the tunnel opening are connected and tightened with a tensioning device when the shield machine receives the pipe segments; After the tensioning device is installed, water and soil cleaning work is carried out. Pumping water and clearing mud requires the cooperation of 3 high-power water pumps and grab buckets. When the water level in the shield receiving well is pumped to a certain level, the earth on the top of the shield machine is grabbed to the ground by a grab bucket, and the soil around the shield machine is manually excavated. When clearing mud, the slope is cleared and the soil at the tunnel entrance is cleared first to ensure timely welding of the arc steel plate and the shield tail; As the mud and water are cleared, curved steel plates are used to weld the steel plates on the end faces of the tunnel gate ring and the steel plates on the shield tail shell to form an effective seal. Six grouting ball valves are pre-installed on the ring plate of the tunnel gate ring and evenly arranged along the tunnel gate ring. After welding, six ball valves are used to grout the tunnel gate to completely seal the tunnel gate. The shield machine is dismantled and hoisted out. After thawing, holes are opened on the pipe segments to check the grouting sealing condition. If the grouting is not dense, continue to add double liquid slurry until multiple holes are opened to check for water leakage.

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