CN104963334B - Reinforced with slip casting freezing pipe and freeze the construction method that service channel suppresses frozen swell and melt settlement - Google Patents

Abstract

The invention relates to a construction method for strengthening the freezing communication channel with a grouting freezing pipe to suppress frost heaving and thawing. By using the freezing pipe as a grouting pipe, it is characterized in that the grouting freezing pipe consists of a grouting pipe I and a liquid supply pipe. The grouting pipe Ⅰ is composed of 3~6 sections, the first section is equipped with a drill bit Ⅲ, and a check valve Ⅳ is arranged on both sides of the pipe body; the liquid supply pipe Ⅱ is made by cross-welding two steel pipes. Adding a certain amount of cement slurry into the soil improves the physical and mechanical properties of the soil, and can inhibit the impact of frost heaving and thawing on the surrounding strata and buildings (structures) when the communication channel is frozen and strengthened. The construction steps are construction preparation → positioning and opening → grouting → installation of liquid supply pipe → installation of refrigeration system → maintenance and completion of starting and freezing. The advantage of this construction method is that the cement-soil reinforcement further strengthens the strength of the soil, enhances the anti-seepage and self-stability of the soil, and the water-tightness of the contact channel strata, effectively controls the seepage of groundwater, and improves the safety of later excavation and construction.

Description

The Construction Method of Reinforcing the Frozen Communication Channel with Grouting and Frozen Pipes to Restrain Frost Heave and Thaw Settlement

technical field

The invention relates to a construction method for using a grouting freezing pipe to reinforce a freezing communication channel and suppress frost heaving and thawing. This method improves the physical and mechanical properties of the soil by adding a certain amount of cement slurry into the soil by using the frozen pipe as the grouting pipe, which can inhibit the impact of frost heaving and thawing on the surrounding strata and buildings (structures) when the connecting channel is frozen and reinforced. impact on buildings.

Background technique

Ningbo, Shanghai, Nanjing and other areas near the river and sea have a wide range of soft soil layers with low soil strength and high water content. In the process of underground engineering construction, many problems such as subsidence and water gushing need to be taken into account, among which the reinforcement of communication channels is the key. Both the artificial freezing method and the cement-soil reinforcement method are commonly used in engineering, and each has advantages and disadvantages.

The freezing method uses artificial freezing and refrigeration technology to freeze the water in the formation, turn the natural rock and soil into frozen soil, increase its strength and stability, and isolate the connection between groundwater and underground engineering, so that under the protection of the frozen wall, Underground engineering excavation and masonry construction. It has the advantages of being able to form frozen soil walls under extremely complex engineering geology and hydrogeology conditions, not being limited by the scope and depth of support, and having strict waterproof and non-pollution properties.

However, after the construction of artificial freezing method, frost heave and thawing phenomenon will occur in the surrounding strata, which will adversely affect the engineering properties of the soil and adjacent buildings for the surrounding environment, such as causing foundation instability and causing adjacent buildings to tilt , cracks, serious accidents such as building collapse, or damage to underground pipelines and other adverse consequences.

After the frozen construction of the contact channel is completed, the ground subsidence is generally controlled by tracking the grouting and filling the soil during the thawing period. It is difficult to completely control the post-construction melt settlement of the soft soil stratum; due to the long influence period of melt settlement, insufficient grouting in the early stage often leads to uneven settlement of the up and down lines during the operation of the subway, causing serious safety hazards.

At present, the methods of forming cement-soil consolidated body in soil use grouting method, deep mixing pile and high-pressure rotary spraying method. This construction method adopts the grouting method.

The grouting method is a construction method in which the cementing material is prepared into a slurry and injected into loose sandy or water-bearing formations, rock formations containing cracks, caves, and broken zones to solidify. After the grout solidifies and hardens, it plays the role of cementation and blockage, which stabilizes the ground and cuts off the water source to ensure smooth construction.

In actual underground engineering, in order to improve the effectiveness of foundation reinforcement, sometimes the comprehensive artificial freezing method and cement-soil reinforcement method are carried out at the same time. For example, during the excavation of a subway tunnel, problems often arise in the construction of the starting, receiving and connecting channels at the end of the shield due to the failure of cement and soil reinforcement. At this time, the freezing method can be used for supplementary reinforcement; When the ground conditions are complex or the surrounding buildings (structures) require very little settlement, first use the cement-soil reinforcement method for foundation treatment, and then carry out artificial freezing method construction on the formed cement-soil foundation.

Contents of the invention

Using the artificial freezing method and the cement-soil reinforcement method to strengthen the foundation at the same time has advantages that cannot be ignored: the cement-soil improves the physical and mechanical properties of the foundation, and when the artificial freezing method is used for construction on this basis, the resulting freeze-thaw damage is suppressed. It avoids problems such as uneven settlement and cracking of the soft soil stratum connection channel and tunnel structure during the operation period caused by insufficient grouting and untimely grouting due to unacceptable conditions in the later period.

The object of the present invention is to provide a construction method for reinforcing the freezing communication channel with the grouting freezing pipe and suppressing the frost heaving and thawing settlement. By using this construction method, the subsidence of the ground can be controlled at 5mm, and the influence range of melting settlement can be controlled at about 24m.

The purpose of the present invention is achieved through the following technical solutions:

A grouting freezing pipe, characterized in that the grouting freezing pipe is composed of a grouting pipe I and a liquid supply pipe II, wherein the grouting pipe I consists of 3 to 6 sections, the end of the first section is equipped with a drill bit III, and the pipe A one-way valve IV is arranged on each side of the body; the liquid supply pipe II is made by cross-welding two steel pipes.

The grouting freezing pipe is characterized in that the grouting pipe I is a Φ89×8mm, 20# low-carbon seamless steel pipe, the length of the first section is 1m, and the length of each subsequent section is 1.5m.

The grouting freezing pipe is characterized in that the liquid supply pipe II is Φ45×3mm, 20# low-carbon seamless steel pipe, one of which is 2-8m in length, and the other is 0.5m in length, welded on On one side of the front end of the 2-8m steel pipe.

The construction method of using the described grouting freezing pipe to strengthen the freezing communication channel and inhibit the frost heaving and thawing settlement is characterized in that the construction steps are as follows:

a. Construction preparation, clearing obstacles in the tunnel, building a construction work platform; connecting power supply lines to meet the needs of drilling construction, freezing system in the tunnel and excavation construction power supply; laying pipelines to the construction work surface of the communication channel for hole positions Drilling and freezing operation for water supply and sewage discharge; check the quality of cement, the working performance of drilling rigs and the integrity of measuring equipment;

b. Positioning and opening, adopt the secondary opening process, according to the position, deflection and depth of the hole position; the drilling rig is in place, choose the MD-60 drilling rig, control the torque 2KN/m, and the thrust 17KN to drill the hole position;

c. After opening the hole, drill the pre-grouting hole into the grouting pipe for grouting. The grouting pipe is Φ89×8mm, 20# low-carbon seamless steel pipe. The length of the first section of the grouting pipe is 1m. The grouting pipe takes 1.5m as a section, and the first section of the grouting pipe is installed with a one-way valve for grouting on the pipe end and the pipe body. The opening pressure of the one-way valve is between 0.3 and 0.5MPa, and the grouting is performed section by section according to the design depth;

d. Grouting parameters. For soft ground, the proportion of cement slurry is 10%. For communication channels with normal buried depth (buried depth ≤ 20m), the grouting pressure is controlled at 0.4-0.5MPa during the grouting process. If the communication channel is buried When the depth is relatively deep (20m<burial depth≤40m), increase the grouting pressure to 0.8-1.0Mpa to ensure uniform grouting, and control the grouting radius at 1.8m-2.0m; the grouting amount is controlled according to the void ratio of the undisturbed soil and The amount of water and soil loss during the drilling process, it is more appropriate for the grout to finally fill 50% to 60% of the undisturbed soil voids;

e. Rotate the grouting pipe to ensure that the cement slurry and soil are fully mixed evenly. After the grouting is completed, press the grouting pipe to remove excess grout, and then install the liquid supply pipe in the grouting pipe as a subsequent freezing pipe, and use a sponge or hair Foam plastic seals the orifice to prevent slurry leakage;

f. Move the drilling rig to the next hole position, the hole position drilling adopts the interval drilling method, and repeat steps b-e until all the grouting holes are grouted;

g. Drilling sequence, the bottom hole of the communication channel should be drilled first, then the hole at the top of the communication channel, and finally the holes on both sides of the communication channel, and the drilling of the holes on both sides of the communication channel can be carried out at the same time;

h. Directly lay out freezing pipes without making holes for grouting. The construction sequence is: positioning openings and installation of orifice pipes → installation of orifice sealing devices → drilling → measurement → closing the bottom of the hole → pressure test.

i. Install a freezing and refrigeration system, arrange temperature measuring holes and pressure relief holes, connect pipelines, install heat preservation equipment, test instruments, dissolve calcium chloride, and fill fluorine and refuel the unit;

j. After the last hole grouting is completed, cure for 14 days, start freezing construction, and keep the lowest salt water temperature at -28～-30°C until the design freezing area is reinforced.

Beneficial effect

Compared with the existing construction method, this construction method of strengthening the freezing communication channel with grouting freezing pipes to suppress frost heaving and thawing has the following beneficial effects:

1. All the existing construction machinery is used, and the operability is strong;

2. The artificial freezing method further strengthens the strength of the soil on the basis of the cement-soil reinforcement method, so that the soil is reinforced, and the anti-seepage and self-stability capabilities are enhanced;

3. The water-tightness of the formation of the communication channel is enhanced, which can effectively control the seepage of groundwater, reduce the impact of high water head pressure, and increase the safety of later excavation and construction;

4. The reinforcement of the cement soil layer can effectively restrain the melting of the surrounding frozen strata and its impact on surrounding buildings and structures;

5. Improvement of cement and soil in advance avoids problems such as incomplete and untimely grouting due to unfavorable conditions in the later period, which will cause uneven settlement and cracking of the soft soil stratum connection channel and tunnel structure during operation, and strengthen the supplementary grouting in the later period. The controllability of the grout and the reduction of the grouting cycle in the later stage can save the amount of cement used, reduce the construction time and the cost of manpower and machinery.

Description of drawings

Figure 1 is a schematic diagram of a grouting freezing tube,

Figure 2 is a schematic diagram of the cement-soil reinforcement sequence and reinforcement area of the communication channel.

Reference signs: Ⅰ—grouting pipe Ⅱ—liquid supply pipe Ⅲ—drill bit Ⅳ—one-way valve Ⅴ—outer boundary of communication channel Ⅵ—freezing hole position (43～54) Ⅶ—grouting freezing hole position (1～42) Ⅷ—Drilling sequence number (1~54).

detailed description

Embodiment 1: A kind of grouting freezing pipe

A subway connection channel in Ningbo, where the geology is from top to bottom, consists of plain fill, silt layer, and silty clay layer. The stratum that the shield tunnels through is mainly silty clay layer. The burial depth of the communication channel is 27.6m, and the reinforcement project adopts the joint reinforcement of cement and soil reinforcement + horizontal freezing method. According to the design requirements, the reinforcement depth of the communication channel is 8.5m.

1. A grouting freezing pipe with a length of 8.5m, characterized in that the grouting freezing pipe is composed of a grouting pipe I and a liquid supply pipe II, wherein the grouting pipe I consists of 6 sections, and the end of the first section is installed There is a drill bit III, and a one-way valve IV is arranged on both sides of the pipe body; the liquid supply pipe II is made by cross-welding two steel pipes.

2. The aforementioned grouting freezing pipe is characterized in that the grouting pipe I is Φ89×8mm, 20# low carbon seamless steel pipe, the length of the first section is 1m, and the length of each subsequent section is 1.5m.

3. The above-mentioned one kind of grouting freezing pipe is characterized in that the liquid supply pipe II is Φ45×3mm, 20# low-carbon seamless steel pipe, one of which is 8.0m in length, and the other is 0.5m in length, welded On one side of the front end of the 8m steel pipe.

Embodiment 2: A kind of grouting freezing pipe

A connecting channel of Suzhou Metro Line 3, the geology of the site is plain fill from top to bottom, silty clay layer, silt-sand interlayer, and silt-fine sand. The stratum traversed by shield tunneling is mainly silt fine sand layer. The communication channel is buried at a depth of 15.2m, and the reinforcement project adopts cement-soil reinforcement + horizontal freezing method for joint reinforcement. According to the design requirements, the reinforcement depth of the communication channel is 4m.

A grouting freezing pipe with a length of 4m, which is characterized in that the grouting freezing pipe is composed of a grouting pipe I and a liquid supply pipe II, wherein the grouting pipe I is composed of three sections, and the end of the first section is equipped with a drill bit Ⅲ, a one-way valve Ⅳ is arranged on both sides of the pipe body; the liquid supply pipe Ⅱ is made by cross-welding two steel pipes.

2. The aforementioned grouting freezing pipe is characterized in that the grouting pipe I is a Φ89×8mm, 20# low-carbon seamless steel pipe, the length of the first section is 1m, and the length of each subsequent section is 1.5m.

3. The above-mentioned one kind of grouting freezing pipe is characterized in that the liquid supply pipe II is Φ45×3mm, 20# low-carbon seamless steel pipe, one of which is 3.5m in length, and the other is 0.5m in length, welded On one side of the front end of the 3.5m steel pipe.

Embodiment 3: A kind of grouting freezing pipe

The geology of a communication channel in Ningbo Metro is plain fill, silty clay layer, and silty fine sand layer from top to bottom. The stratum traversed by shield tunneling is mainly silt fine sand layer. The communication channel is buried at a depth of 21.8m, and the reinforcement project adopts cement-soil reinforcement + horizontal freezing method for joint reinforcement. According to the design requirements, the reinforcement depth of the communication channel is 7m.

A grouting freezing pipe with a length of 7m, which is characterized in that the grouting freezing pipe is composed of a grouting pipe I and a liquid supply pipe II, wherein the grouting pipe I is composed of 5 sections, and the end of the first section is equipped with a drill bit Ⅲ, a one-way valve Ⅳ is arranged on both sides of the pipe body; the liquid supply pipe Ⅱ is made by cross-welding two steel pipes.

2. The aforementioned grouting freezing pipe is characterized in that the grouting pipe I is Φ89×8mm, 20# low carbon seamless steel pipe, the length of the first section is 1m, and the length of each subsequent section is 1.5m.

3. The above-mentioned one kind of grouting freezing pipe is characterized in that the liquid supply pipe II is Φ45×3mm, 20# low-carbon seamless steel pipe, one of which is 6.5m in length, and the other is 0.5m in length, welded On one side of the front end of the 6.5m steel pipe.

Example 4: A construction method of using grouting frozen pipes to reinforce the frozen communication channel and suppress frost heaving and thawing

A subway connection channel in Ningbo, where the geology is from top to bottom, consists of plain fill, silt layer, and silty clay layer. The stratum that the shield tunnels through is mainly silty clay layer. The burial depth of the communication channel is 27.6m, and the reinforcement project adopts the joint reinforcement of cement and soil reinforcement + horizontal freezing method. According to the design requirements, the reinforcement depth of the communication channel is 8.5m.

A construction method using grouting freezing pipes to reinforce the freezing communication channel to suppress frost heave and thawing settlement, the construction steps are as follows:

1. Construction preparation, clearing obstacles in the tunnel, building a construction work platform; connecting power supply lines to meet the needs of drilling construction, freezing system in the tunnel and excavation construction power supply; laying pipelines to the construction work surface of the communication channel for hole positions Drilling and freezing operation for water supply and sewage discharge; check the quality of cement, the working performance of drilling rigs and the integrity of measuring equipment;

2. Locate the opening, use theodolite and compass to determine the inclination and azimuth angle of the opening, accurately determine the position and direction of the opening, and arrange points on the two sides of the tunnel, adopt the secondary opening process, and use the wire drawing method to verify and control the hole Position direction; the drilling rig is in place, select the MD-60 drilling rig, adjust the drilling rig position, control the torque 2KN/m, and thrust 17KN to drill the No. 1 hole;

3. Drill the No. 1 hole into the grouting pipe for grouting. The grouting pipe is Φ89×8mm, 20# low-carbon seamless steel pipe. The length of the first section of the grouting pipe is 1m, and a one-way valve is installed at the end of the pipe , the opening pressure of the one-way valve is between 0.3-0.5MPa, according to the design depth of 8.5m, the length of the subsequent grouting pipes is 1.5m, and the grouting is performed section by section;

4. The proportion of cement slurry is 10%. During the grouting process, the grouting pressure is controlled at 0.8-1.0MPa, the grouting radius is controlled at 2.0m, and the amount of grouting is controlled according to the void ratio of the undisturbed soil and the amount of water and soil loss during the drilling process. Fill 50% to 60% of the voids in the undisturbed soil;

5. Rotate the grouting pipe to ensure that the cement slurry and the soil are fully mixed evenly. After the grouting is completed, install the liquid supply pipe in the grouting pipe as a subsequent freezing pipe. The liquid supply pipe is made of Φ45×3mm, 20# low-carbon seamless steel pipe. Sponge or foam plastic to seal the orifice to prevent slurry leakage;

6. Move the drilling rig to the No. 2 hole, and the hole is drilled using the interval drilling method (see Figure 2 for the detailed drilling and grouting sequence), and repeat steps 2-6 until the construction of the cement-soil reinforcement area is completed;

7. Drilling sequence: Drill the holes at the bottom of the communication channel first (hole number 1 to hole number 17), then to the top holes of the communication channel (hole number 18 to hole number 34), and finally to the holes on both sides of the communication channel (hole number 35~hole number 42), the drilling of the holes on both sides of the communication channel can be carried out at the same time;

8. Arrange the freezing pipes. According to the design of the freezing curtain, the number of freezing holes is 54. The distance between the holes in the upper and lower parts of the communication channel is 0.7m, and the distance between the holes on the left and right sides is 0.6m; no grouting is required for hole numbers 43 to 54 For hole use, directly install the freezing pipe; the construction sequence is: positioning opening and orifice pipe installation→orifice sealing device installation→drilling→measurement→closing the bottom of the hole→pressure test.

9. Install a freezing refrigeration system, which can be installed synchronously during the drilling and grouting process to save time; the equipment in the freezing station mainly includes 2 YSLGF300Ⅱ screw units (one spare), the maximum cooling capacity is about 87500kcal/h, The total motor power of the refrigerating unit is 110kw; 2 sets of IS150-125-250 brine circulating pumps (1 spare), the flow rate is 200m3/h, the head is 30m, and the total motor power is 30kw; 1 set of IS150-125-250 cooling water circulating pump, the flow rate is 200m3/h h, head 30m, total motor power 30kw; 2 cooling towers, total motor power 6kw; one brine tank, volume 6m3; after that, connect pipelines, install heat preservation equipment and test instruments, and use Φ159× for brine dry pipes and collection and distribution pipes 5mm seamless steel pipe, Φ1.5" high-pressure rubber hose is used for the connection between the collection and distribution pipes and horns; the Φ5" welded pipe is used for the cooling water pipe; the Φ1.5" pipe is used for the freezing plate; , Install pressure and temperature sensors and control valves on the brine pipe of the loop, install a flow meter at the outlet of the brine pipe, and install a liquid level sensor in the brine tank; install two valves between the liquid distribution ring and the freezer to control the brine flow of the freezer ;Install an air release valve at the height of the brine pipeline; install a one-way valve on the outgoing brine main pipe; The unit is filled with fluorine and refueled, and the specific gravity of brine is 1.26-1.27;

10. After the last grouting hole is cured for 14 days, start freezing construction. The active freezing time is 40 days. The temperature is around -28°C until the construction of the main structure of the communication channel is completed.

Example 5: A construction method of using grouting frozen pipes to reinforce the frozen communication channel and suppress frost heaving and thawing

A connecting channel of Suzhou Metro Line 3, the geology of the site is plain fill from top to bottom, silty clay layer, silt-sand interlayer, and silt-fine sand. The stratum traversed by shield tunneling is mainly silt fine sand layer. The communication channel is buried at a depth of 15.2m, and the reinforcement project adopts cement-soil reinforcement + horizontal freezing method for joint reinforcement. According to the design requirements, the reinforcement depth of the communication channel is 4.0m.

A construction method using grouting freezing pipes to reinforce the freezing communication channel to suppress frost heave and thawing settlement, the construction steps are as follows:

1. Construction preparation, clearing obstacles in the tunnel, building a construction work platform; connecting power supply lines to meet the needs of drilling construction, freezing system in the tunnel and excavation construction power supply; laying pipelines to the construction work surface of the communication channel for hole positions Drilling and freezing operation for water supply and sewage discharge; check the quality of cement, the working performance of drilling rigs and the integrity of measuring equipment;

2. Locate the opening, use theodolite and compass to determine the inclination and azimuth angle of the opening, accurately determine the position and direction of the opening, and arrange points on the two sides of the tunnel, adopt the secondary opening process, and use the wire drawing method to verify and control the hole Position direction; the drilling rig is in place, select the MD-60 drilling rig, adjust the drilling rig position, control the torque 2KN/m, and thrust 17KN to drill the No. 1 hole;

3. Drill the No. 1 hole into the grouting pipe for grouting. The grouting pipe is Φ89×8mm, 20# low-carbon seamless steel pipe. The length of the first section of the grouting pipe is 1m, and a one-way valve is installed at the end of the pipe , the opening pressure of the one-way valve is between 0.3-0.5MPa, according to the design depth of 4.0m, the length of the subsequent grouting pipes is 1.5m, and the grouting is performed section by section;

4. The proportion of cement slurry is 10%. During the grouting process, the grouting pressure is controlled to be 0.4-0.5MPa, the grouting radius is controlled to be 1.8m, and the amount of grouting is controlled according to the void ratio of the undisturbed soil and the amount of water and soil loss during the drilling process. Fill 50% to 60% of the voids in the undisturbed soil;

5. Rotate the grouting pipe to ensure that the cement slurry and the soil are fully mixed evenly. After the grouting is completed, install the liquid supply pipe in the grouting pipe as a subsequent freezing pipe. The liquid supply pipe is made of Φ45×3mm, 20# low-carbon seamless steel pipe. Sponge or foam plastic to seal the orifice to prevent slurry leakage;

6. Move the drilling rig to the No. 2 hole, and the hole is drilled using the interval drilling method (see Figure 2 for the detailed drilling and grouting sequence), and repeat steps 2-6 until the construction of the cement-soil reinforcement area is completed;

7. Drilling sequence: Drill the holes at the bottom of the communication channel first (hole number 1 to hole number 17), then to the top holes of the communication channel (hole number 18 to hole number 34), and finally to the holes on both sides of the communication channel (hole number 35~hole number 42), the drilling of the holes on both sides of the communication channel can be carried out at the same time;

8. Arrange the freezing pipes. According to the design of the freezing curtain, the number of freezing holes is 54. The distance between the holes in the upper and lower parts of the communication channel is 0.7m, and the distance between the holes on the left and right sides is 0.6m; no grouting is required for hole numbers 43 to 54 For hole use, directly install the freezing pipe; the construction sequence is: positioning opening and orifice pipe installation→orifice sealing device installation→drilling→measurement→closing the bottom of the hole→pressure test.

9. Install a freezing refrigeration system, which can be installed synchronously during the drilling and grouting process, saving time; the equipment in the freezing station mainly includes 2 YSLGF300Ⅱ screw units (one spare), the maximum cooling capacity is about 84500kcal/h, The total motor power of the refrigerating unit is 110kw; 2 sets of IS150-125-250 brine circulating pumps (1 spare), the flow rate is 200m3/h, the head is 30m, and the total motor power is 30kw; 1 set of IS150-125-250 cooling water circulating pump, the flow rate is 200m3/h h, head 30m, motor total power 30kw; 2 cooling towers, motor total power 8kw; one brine tank, volume 6m3; after connecting pipelines, installing heat preservation equipment and test instruments, brine dry pipes and collection and distribution pipes are all made of Φ159× 5mm seamless steel pipe, Φ1.5" high-pressure rubber hose is used for the connection between the collection and distribution pipes and horns; the Φ5" welded pipe is used for the cooling water pipe; the Φ1.5" pipe is used for the freezing plate; , Install pressure and temperature sensors and control valves on the brine pipe of the loop, install a flow meter at the outlet of the brine pipe, and install a liquid level sensor in the brine tank; install two valves between the liquid distribution ring and the freezer to control the brine flow of the freezer ;Install an air release valve at the height of the brine pipeline; install a one-way valve on the outgoing brine main pipe; The unit is filled with fluorine and refueled, using N46 refrigeration oil, R22 refrigerant, and the specific gravity of the brine solution is 1.27;

10. After the last grouting hole is cured for 14 days, start freezing construction. The active freezing time is 40 days. The temperature is around -28°C until the construction of the main structure of the communication channel is completed.

Example 6: A construction method of using grouting frozen pipes to reinforce the frozen communication channel and suppress frost heaving and thawing

The geology of a communication channel in Ningbo Metro is plain fill, silty clay layer, and silty fine sand layer from top to bottom. The stratum traversed by shield tunneling is mainly silt fine sand layer. The communication channel is buried at a depth of 21.8m, and the reinforcement project adopts cement-soil reinforcement + horizontal freezing method for joint reinforcement. According to the design requirements, the reinforcement depth of the communication channel is 7m.

A construction method using grouting freezing pipes to reinforce the freezing communication channel to suppress frost heave and thawing settlement, the construction steps are as follows:

1. Construction preparation, clearing obstacles in the tunnel, building a construction work platform; connecting power supply lines to meet the needs of drilling construction, freezing system in the tunnel and excavation construction power supply; laying pipelines to the construction work surface of the communication channel for hole positions Drilling and freezing operation for water supply and sewage discharge; check the quality of cement, the working performance of drilling rigs and the integrity of measuring equipment;

2. Locate the opening, use theodolite and compass to determine the inclination and azimuth angle of the opening, accurately determine the position and direction of the opening, and arrange points on the two sides of the tunnel, adopt the secondary opening process, and use the wire drawing method to verify and control the hole Position direction; the drilling rig is in place, select the MD-60 drilling rig, adjust the drilling rig position, control the torque 2KN/m, and thrust 17KN to drill the No. 1 hole;

3. Drill the No. 1 hole into the grouting pipe for grouting. The grouting pipe is Φ89×8mm, 20# low-carbon seamless steel pipe. The length of the first section of the grouting pipe is 1m, and a one-way valve is installed at the end of the pipe , the opening pressure of the one-way valve is between 0.3-0.5MPa, according to the design depth of 7.0m, the length of the subsequent grouting pipes is 1.5m, and the grouting is performed section by section;

4. The proportion of cement slurry is 10%. During the grouting process, the grouting pressure is controlled to be 0.8-0.9MPa, the grouting radius is controlled to be 1.9m, and the amount of grouting is controlled according to the void ratio of the undisturbed soil and the amount of water and soil loss during the drilling process. Fill 50% to 60% of the voids in the undisturbed soil;

5. Rotate the grouting pipe to ensure that the cement slurry and the soil are fully mixed evenly. After the grouting is completed, install the liquid supply pipe in the grouting pipe as a subsequent freezing pipe. The liquid supply pipe is made of Φ45×3mm, 20# low-carbon seamless steel pipe. Sponge or foam plastic to seal the orifice to prevent slurry leakage;

6. Move the drilling rig to the No. 2 hole, and the hole is drilled using the interval drilling method (see Figure 2 for the detailed drilling and grouting sequence), and repeat steps 2-6 until the construction of the cement-soil reinforcement area is completed;

7. Drilling sequence: Drill the holes at the bottom of the communication channel first (hole number 1 to hole number 17), then to the top holes of the communication channel (hole number 18 to hole number 34), and finally to the holes on both sides of the communication channel (hole number 35~hole number 42), the drilling of the holes on both sides of the communication channel can be carried out at the same time;

8. Arrange the freezing pipes. According to the design of the freezing curtain, the number of freezing holes is 54. The distance between the holes in the upper and lower parts of the communication channel is 0.7m, and the distance between the holes on the left and right sides is 0.6m; no grouting is required for hole numbers 43 to 54 For hole use, directly install the freezing pipe; the construction sequence is: positioning opening and orifice pipe installation→orifice sealing device installation→drilling→measurement→closing the bottom of the hole→pressure test.

9. Install the freezing refrigeration system, which can be installed synchronously during the drilling and grouting process to save time; the equipment in the freezing station mainly includes 2 YSLGF300Ⅱ screw units (one spare), the maximum cooling capacity is about 84500kcal/h, The total motor power of the refrigerating unit is 110kw; 2 sets of IS150-125-250 brine circulation pumps (1 spare), the flow rate is 200m3/h, the head is 30m, and the total power of the motor is 30kw; 1 set of IS150-125-250 cooling water circulation pump, the flow rate is 200m3/h h, head 30m, motor total power 30kw; 2 cooling towers, motor total power 8kw; one brine tank, volume 6m3; after connecting pipelines, installing heat preservation equipment and test instruments, brine dry pipes and collection and distribution pipes are all made of Φ159× 5mm seamless steel pipe, Φ1.5" high-pressure rubber hose for the connection between the collection and liquid distribution pipes and horns; Φ5" welded pipes for cooling water pipes; Φ1.5" pipes for freezing plates; , Install pressure and temperature sensors and control valves on the brine pipe of the circuit, install a flow meter at the outlet of the brine pipe, and install a liquid level sensor in the brine tank; install two valves between the liquid distribution ring and the freezer to control the brine flow of the freezer ;Install an air release valve at the height of the brine pipeline; install a one-way valve on the outgoing brine main pipe; The unit is filled with fluorine and refueled, using N46 refrigeration oil, R22 refrigerant, and the specific gravity of the brine solution is 1.27;

10. After the last grouting hole is cured for 14 days, start freezing construction. The active freezing time is 40 days. The temperature is around -28°C until the construction of the main structure of the communication channel is completed.

Claims (1)

1. Freeze the construction method that service channel suppresses frozen swell and melt settlement 1. being reinforced with slip casting freezing pipe, it is characterised in that described slip casting Freezing pipe is by Grouting Pipe（Ⅰ）And feed pipe（Ⅱ）Composition；Described Grouting Pipe（Ⅰ）It is made up of 3 ~ 6 sections, Section 1 pipe end is equipped with brill Head（Ⅲ）, a check valve is respectively arranged in pipe shaft both sides（Ⅳ）, Grouting Pipe（Ⅰ）For 89 × 8mm of Φ, 20# low-carbon seamless steel pipes, the 1st Section length is 1m, and the 2nd ~ 6 section length is 1.5m；Described feed pipe（Ⅱ）For 45 × 3mm of Φ, 20# low-carbon seamless steel pipes, by two Individual steel pipe cross weld is made, 2 ~ 8m of one of steel pipe length, and the long 0.5m of another steel pipe is welded on 2~8m steel pipes front end On one side；Reinforced with slip casting freezing pipe and freeze the construction method that service channel suppresses frozen swell and melt settlement, it is characterised in that construction step It is rapid as follows：

   A, preparation of construction：Barrier in tunnel is cleared up, construction operation platform is built；Connect supply line, with meet drilling construction, Freezing system and excavation construct the demand of power supply in tunnel；Pipeline is laid to Freezing Method for Cross-passage Construction working face, is drilled for hole position And freeze operating water supply and blowdown；Check cement quality, rig service behaviour and the intact degree of measuring equipment；

   B, locating holes are to take secondary hole opening technology, according to hole position position, deflection, depth that rig is in place, are bored from MD-60 Machine, control mode 2KN/m, thrust 17KN carries out hole position and is drilled with；

   After c, perforate are finished, pre-pouring grout hole position is pierced Grouting Pipe carry out slip casting, Grouting Pipe from Φ 89 × 8mm, 20# low-carbons without Steel pipe is stitched, Section 1 slip casting length of tube is 1m, and follow-up Grouting Pipe is using 1.5m as a section, and Section 1 Grouting Pipe pipe end and pipe shaft install single To valve slip casting, check valve opens pressure between 0.3 ~ 0.5MPa, according to projected depth slip casting section by section；

   D, grouting parameter：For soft soil layer, cement grout proportioning selects 10%, for the service channel of normal buried depth, i.e. buried depth ≤ 20m, during slip casting control 0.4 ~ 0.5MPa of grouting pressure, for the service channel that buried depth is deeper, i.e. 20m ＜ buried depths≤ During 40m, grouting pressure is increased to 0.8 ~ 1.0MPa, it is ensured that slurries diffusion is uniform, control slip casting radius is in 1.8m-2.0m；Slip casting Amount control is according to undisturbed soil hole when boring procedure soil erosion amount, until slurries amount finally fills the 50% ~ 60% of undisturbed soil Hole；

   E, rotation Grouting Pipe, it is ensured that cement mortar is sufficiently mixed uniformly with soil, and slip casting is suppressed after finishing to Grouting Pipe, is excluded many Remaining slurry liquid, feed pipe formation slip casting freezing pipe is then disposed in Grouting Pipe and is subsequently being used as freezing pipe, is sealed using sponge Plug-hole mouthful, leaks outside to prevent slurries；

   F, mobile drill are to next hole position, and hole position is drilled with is drilled method, and repeat step b ~ e using interval, until all slip castings Hole slip casting is finished；

   G, drilling sequences：It is preferential that contact channel bottom hole position is drilled with, it is finally connection then to hole position at the top of service channel Network passage both sides hole position, service channel both sides hole position is drilled with to be carried out simultaneously；

   H, do not make grouting hole and directly arrange freezing pipe, sequence of construction is：Locating holes and orifice tube installation → orifice sealing dress Put installation → drilling → measurement → blind hole bottom → bulge test；

   I, installation freeze refrigeration system, and arrangement thermometer hole, relief hole, connecting line install heat-preserving equipment, test instrumentation, dissolving Calcium chloride and unit is filled fluorine oiling；

   J, treat to conserve 14 days after the completion of last hole slip casting, start frozen construction, keep brine temp -28~-30 DEG C, until Design frozen region and reinforce completion.