CN114855874A

CN114855874A - Open excavation and freezing underground excavation combined construction method for underground communication passage access close to existing structure through pipe gallery

Info

Publication number: CN114855874A
Application number: CN202210547579.8A
Authority: CN
Inventors: 杨平; 韩琳亮; 冯俊青; 陈潋; 杨宁; 张婷; 何文龙
Original assignee: Huadong Construction Co ltd Of China Railway No3 Engineering Group Co ltd; Nanjing Forestry University
Current assignee: Huadong Construction Co ltd Of China Railway No3 Engineering Group Co ltd; Nanjing Forestry University
Priority date: 2022-04-29
Filing date: 2022-04-29
Publication date: 2022-08-05

Abstract

The invention discloses an open excavation and freezing underground excavation combined construction method of an underground communication passage access close to an existing structure underground pipe gallery, which specifically comprises open excavation section construction connected with an existing subway access and underground excavation section construction of the existing underground pipe gallery. The construction method effectively reduces the stratum disturbance in the construction process of the underground communicating channel, avoids the influence on the existing construction, and ensures safe and reliable construction of the underground communicating channel access close to the pipe gallery under the existing structure by forming the frozen cement soil with high strength and water stop performance at the underground excavation section.

Description

Open excavation and freezing underground excavation combined construction method for underground communication passage access close to existing structure through pipe gallery

Technical Field

The invention belongs to the technical field of underground engineering construction, and relates to a combined construction method of open excavation and freezing underground excavation of an underground communication passage access close to an existing structure lower pipe gallery.

Background

With the development of urban underground space, in order to realize better building functions, an underground communication channel is often built between peripheral buildings or subway station entrances and exits, and the like, so that the problems of deformation, cracking, water seepage and the like of the existing buildings are easily caused by the situation that the existing buildings nearby are sensitive to excavation and are easily disturbed, the safe use of the existing buildings is influenced, and the construction safety and risk prevention and control of the underground communication channel are difficult.

The underground communication passageway access & exit of wearing piping lane under present generally includes open cut section and undercut section passageway, and wherein the undercut section is the most critical part in whole work progress, handles improperly, can cause the destruction of upper portion piping lane. Traditional undercut section reinforcement method mostly adopts slip casting method, all-round injection slip casting or freezing method etc. nevertheless adopts a reinforcement method alone, often because strengthen body intensity and quality not enough, or because of arousing peripheral great frost heaving melt and sink deformation, is difficult to satisfy the construction demand, and the concrete expression is: 1) when the grouting method is used for reinforcement, construction is simple, operation is convenient, but the grouting pressure in the grouting process is too high, so that the existing pipe gallery is easy to bulge, the grouting pressure is low, the grouting effect is poor, soil body collapse is easy to occur in the excavation process, so that settlement displacement is caused, the safety of the existing structure is influenced, and the water cut-off property in an underground water-bearing layer is difficult to guarantee; 2) when the freezing method is used, the problem of frost heaving and thaw collapse can be caused in the freezing process, so that the upper soil body is raised or settled, and the structure is influenced; 3) when the omnibearing spraying grouting is used, the underground pressure can be strictly controlled, the influence on the existing upper building is reduced, but the reinforcing uniformity and the water stopping performance are not easy to control, and the danger of water inrush and the like can be caused in the excavation process.

Disclosure of Invention

The technical problem to be solved is as follows: in order to overcome the defects of the prior art, reduce the disturbance to the adjacent structure while reinforcing and stopping water, strictly control the deformation of the upper pipe gallery and reduce the risk of underground excavation construction, the invention provides a combined construction method of open excavation and freezing underground excavation of an underground communication passage access opening which is adjacent to the existing structure and penetrates through the pipe gallery.

The technical scheme is as follows: a method for open excavation and freezing underground excavation combined construction of an underground communication passage access close to an existing structure through a pipe gallery comprises the following steps:

s1, determining the construction positions of the open excavation section where the underground communication passage access is connected with the existing subway access and the underground excavation section where the pipe gallery is penetrated, firstly reinforcing the foundation of the open excavation section and constructing the enclosure structure, and applying a crown beam and a concrete support.

S2, excavating the open cut sections in layers, erecting horizontal inner supports, constructing an open cut section channel structure after excavating to the designed depth, reserving soil holes in the open cut section on one side close to the channel of the open cut section, constructing a temporary retaining wall above the top plate of the soil holes, and backfilling the earthwork on the top plate of the open cut section.

S3, reinforcing and constructing the underground excavation section MJS: adopting a total station instrument to measure and place the pile position, and rechecking a measuring reference point, a leveling point and a building datum line before measuring and placing the pile position; installing an orifice sealing and spray stopping device, conducting hole construction, drilling a designed depth on a bentonite slurry retaining wall, and measuring the deviation condition of a drilled hole by using a high-precision inclinometer; injecting grouting, closely paying attention to the in-ground pressure and the mud discharge condition in the injecting grouting process, and simultaneously monitoring the deformation of the existing upper building structure: and (5) hole sealing and maintaining, and repeating the steps until the MJS reinforcement body is completely constructed.

S4, reinforcing construction of the underground excavation section by a horizontal freezing method: leveling a field and entering a material field; constructing a freezing pipe; freezing installation and freezing system installation; actively freezing; and monitoring the development of the freezing system and the freezing curtain.

And S5, excavating the underground excavation section until the underground excavation section reaches the receiving well, and finishing the hole entering.

Preferably, the open cut section foundation reinforcement adopts triaxial mixing piles with the diameter of 800mm and the interval of 600mm, the cement mixing amount above the excavation surface of the foundation pit is 7 percent, the cement mixing amount below the bottom of the foundation pit is 18 percent, and the open cut section enclosure structure consists of single-row drilling secant piles with the diameter of 1000mm and the interval of 1200 mm.

Preferably, the soil body between the triaxial mixing pile and the enclosure pile is reinforced by adopting a jet grouting pile, and the dosage of P42.5 ordinary portland cement and cement is 370 kg/m.

Preferably, the triaxial mixing pile and the jet grouting pile are tested by drilling and coring, open-cut section foundation pit excavation can be performed after the design strength reaches 80%, the curing age of the mixing pile is not less than 28 days, the lateral-line-free compressive strength of the cement soil is not less than 1.0MPa, and the permeability coefficient is not more than 1E-8 cm/s.

Preferably, in the injection grouting process, the underground pressure is controlled to be 1.3-1.6 times of the pressure of the original stratum, the water cement ratio is 1.1, the cement doping is more than 45%, the cement slurry pressure is 38-42 MP, the cement slurry flow is 90-130L/min, the step distance stroke is 25mm, and the step distance lifting time is 60 s.

Preferably, the MJS reinforcing bodies are semicircular piles with the diameter of 2600mm, two rows are arranged at the bottom of an excavation area of the underground excavation communicating channel, the pile spacing is 1700mm, the row spacing is 700mm, one row is arranged at the top and two sides, the pile spacing is 700mm, the pile length is not less than the length of the underground excavation channel, and the levelness of the MJS pile is not more than 1/150.

Preferably, the horizontal freezing method reinforcement construction is performed after the MJS reinforcement maintenance 28 in step S3, and the horizontal freezing range is within the MJS reinforcement.

Preferably, according to the excavation pilot tunnel subregion, freezing the pipe and taking the form of "field" font and arranging: two rows of freezing pipes are arranged at the bottom and distributed in a quincunx shape, the rest freezing pipes are arranged in a single row, the freezing pipes are seamless steel pipes with the outer diameter of 89mm and the wall thickness of 10mm, the distance is not more than 900mm, temperature measuring holes are arranged in the freezing reinforcement range, and pressure relief holes are arranged in the freezing area.

Preferably, the temperature of the saline water is reduced to below-18 ℃ after being actively frozen for 7 days, the temperature of the saline water is reduced to below-24 ℃ after being actively frozen for 15 days, the temperature of the saline water is reduced to below-28 ℃ before excavation, and the temperature difference of the saline water in the removing and returning circuits is not more than 2 ℃.

Preferably, the thickness of the frozen curtain is not less than 2m, the average temperature of the frozen curtain is not more than-10 ℃, and the excavation section excavation can be carried out when the average temperature of the interface of the frozen curtain and the enclosure structure is not more than-5 ℃.

Has the advantages that:

(1) according to the open excavation and freezing underground excavation combined construction method for the underground communication passage access close to the existing structure through the pipe gallery, the open excavation section adopts the drilled secant pile and the steel pipe inner support, the triaxial mixing pile is used for reinforcing the interior of the foundation pit, and the early deformation in the excavation process and the influence on the existing structure in the excavation process can be effectively reduced. (2) The underground excavation part is reinforced by adopting an MJS + horizontal freezing method, the MJS cement soil effectively inhibits the frost heaving and thawing sinking phenomenon generated by the freezing method, the frozen cement soil with strong deformation resistance is formed, and the reinforcing effect is reliable. (3) The influence on the surrounding environment is small, and the safe operation of surrounding sensitive building structures is effectively protected.

Drawings

FIG. 1 is a plan view of the port passage structure in example 1

FIG. 2 is a plan view showing the reinforcement of the doorway channel in example 1

FIG. 3 is a floor plan view of the reinforcement of the undercut segment MJS in example 1

FIG. 4 is a plan view of a freezing pipe of a subsurface excavated segment in example 1

In the figure: 1. the method comprises the following steps of open excavation, 2, underground excavation, 3, comprehensive pipe gallery, 4, existing subway entrance and exit, 5, stairs, 6, drilling secant pile, 7, three-shaft stirring pile, 8, rotary spraying pile, 9, MJS + freezing method reinforcing area, 10, underground excavation channel lining, 11, MJS reinforcing body, 12, freezing pipe, 13, temperature measuring hole, 14 and pressure relief hole.

Detailed Description

In the description of the present invention, the directional relationships indicated by "upper", "lower", "top", "bottom", "inner", "outer", etc., are the directional relationships shown in the drawings, and are used for convenience in description of the present invention, rather than to indicate or imply a specific direction of orientation. The specific features in the implementation steps are detailed description of the technical scheme, and are not limiting on the technical scheme of the application. I.e. the technical features in the implementation steps may be combined with each other without conflict. In order to make the technical means, the creation characteristics, the achievement purposes and the effects of the invention easy to understand, the technical scheme is further explained by combining the drawings and the specific implementation modes of the specification. In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to the accompanying drawings.

In order to make the present invention easier to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

In order to realize better building function and effect, an underground communication channel is built between the Zhengrong G64 land and the access of the station of the existing subway station No. S3. As shown in fig. 1, an entrance and an exit of a newly-built underground communication channel are divided into two sections, an open cut section 1 is connected with an entrance and an exit 4 of an existing station with a line of No. S3, and the depth of a foundation pit is 9.997-17.73 m; the existing comprehensive pipe gallery 3 is penetrated under the underground excavation section 2, and the underground excavation burial depth is 15.03 m.

The land form of a project site is relatively flat and belongs to a Yangtze river flood landform unit, and the site of an access of an underground communication channel sequentially comprises miscellaneous filling, silt clay (1), silt clay (2), silt clay-silt soil-sandwiched silt clay (1), silt sand (1) and strongly weathered muddy siltstone from top to bottom. After the underground communication passage is excavated, silt silty clay and silty soil are filled in the basement of the underground communication passage, the basement is soft flow plastic, and the engineering geological performance is poor.

The important engineering difficulty is as follows: 1) the soil quality is poor, the geological condition is poor, the excavated section is large, collapse, roof fall and water gushing are easy to occur, and the safety risk is extremely high; 2) the distance is short, the clear distance between the existing comprehensive pipe gallery 3 and the underground excavation section 2 is 1.642m, the clear distance between the existing comprehensive pipe gallery 3 and the open excavation section 1 is 2.991m, and the influence on the comprehensive pipe gallery 3 during construction is large; 3) the standard is high, and utility tunnel 3 and internal pipeline deformation control standard are high, need study safe and reliable's protection scheme, guarantee the normal operating of internal pipeline during the intercommunication says the construction.

In order to ensure the safe construction of the engineering and not to influence the normal operation of the existing comprehensive pipe gallery 3 in the construction process, the construction method is adopted to construct the access of the underground communication passage, and the specific construction process is as follows:

1. determining the construction positions of an open excavation section 1 connected with an underground passage access 4 and an underground excavation section 2 of a lower through pipe gallery 3 of the underground communication passage according to a design drawing, firstly reinforcing soil in a foundation pit by adopting triaxial mixing piles 7 with the diameter of 800mm and the interval of 600mm, reinforcing the soil above the excavation surface of the foundation pit by 7 percent and reinforcing the soil below the foundation pit by 18 percent, constructing single-row drilling secant piles 6 with the diameter of 1000mm and the interval of 1200mm around the open excavation section, and reinforcing the soil between the drilling secant piles 6 and the triaxial mixing piles 7 by using triple-pipe rotary spraying piles 8 to construct crown beams and concrete supports.

2. The curing age of the triaxial mixing pile 7 is not less than 28 days, the lateral-line-free compressive strength of cement soil is not lower than 1.0MPa, the permeability coefficient is not more than 1E-8cm/s, the triaxial mixing pile 7 and the jet grouting pile 6 are tested by drilling and coring, pit excavation is carried out after the design strength reaches 80%, the open excavation section 1 is excavated in a layered mode, a horizontal inner support is erected, after excavation is carried out to the design depth, a bottom cushion layer and a waterproof layer are constructed, a bottom plate, a side wall and a top plate structure are poured, an upper support is dismantled, 5500mm multiplied by 5500mm soil outlet holes are reserved in the open excavation section on one side close to the underground excavation channel, a temporary retaining wall is constructed above the soil outlet hole top plate, the thickness of the temporary retaining wall is 300mm, and the upper earthwork of the top plate of the open excavation section is backfilled.

3. Constructing MJS reinforcement around an excavation area of the underground excavation section: the total station measures and puts the pile position, should recheck and measure datum point, level point and building the structure datum line before the pile position is measured and put; installing an orifice sealing and spray stopping device, conducting hole leading construction, adopting bentonite slurry to protect the wall of a hole for drilling in order to prevent the hole wall from collapsing and burying the hole, and adopting a high-precision inclinometer to measure the deflection condition of the hole; injecting grouting, wherein the underground pressure and the mud discharge condition are closely concerned in the injecting grouting process; hole sealing maintenance, namely repeating the steps until the MJS reinforcement body 11 is completely constructed; the horizontal MJS reinforcement body 11 is a semicircle with the diameter of 2600mm, two rows are arranged at the bottom of an excavation area of an underground excavation communication channel, the pile spacing is 1700mm, the row spacing is 700mm, one row is arranged at the top and two sides, the pile spacing at two sides is 700mm, the plane arrangement of the MJS reinforcement body 11 is shown in figure 3, and the specific MJS construction parameters are shown in Table 1.

TABLE 1 MJS construction parameters

4. And (3) performing freezing construction after the MJS reinforcement body 11 is maintained for 28 days: leveling a field and entering a material field; drilling construction; freezing installation and freezing system installation; actively freezing; totally arranging 65 freezing pipes 12 around the excavated pilot tunnel, selecting seamless steel pipes with the outer diameter of 89mm and the wall thickness of 10mm to be arranged along the full length of the underground excavation section, arranging a maximum allowable deflection value of the freezing pipes of 150mm, arranging temperature measuring holes 13 in a freezing reinforcement range, and arranging pressure relief holes 14 in a freezing area for measuring unfrozen soil: the specific plan layout of the freezing tubes 12 is shown in fig. 4.

5. Monitoring the temperature of brine in a freezing system and a loop, the flow of a circulating brine pipeline, a freezing curtain temperature field, the pressure of a pressure relief hole 14 and the like during freezing, actively freezing the brine for 7 days until the temperature is reduced to below 18 ℃ below zero, actively freezing the brine for 15 days until the temperature is reduced to below 24 ℃ below zero, reducing the temperature of the brine before excavation to below 28 ℃ below zero, ensuring that the temperature difference of the brine in the freezing system and the loop is not more than 2 ℃, the thickness of the freezing curtain is not less than 2m, the average temperature of the freezing curtain is not more than 10 ℃ below zero, ensuring that the average temperature of the interface between the freezing curtain and the enclosure structure is not more than 5 ℃ below zero, and excavating an underground excavation section.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims

1. A combined construction method of open excavation and freezing underground excavation of an underground communication passage access close to an existing structure through a pipe gallery is characterized by comprising the following steps:

S2, excavating the open cut sections in layers, erecting horizontal inner supports, constructing an open cut section channel structure after excavating to the designed depth, reserving soil holes in the open cut section on one side close to the underground cut channel, constructing a temporary retaining wall above a soil hole top plate, and backfilling the earthwork on the top plate of the open cut section.

S3, reinforcing and constructing the underground excavation section MJS: adopting a total station instrument to measure and place the pile position, and rechecking the measuring datum point, the level point and the building datum line before measuring and placing the pile position; installing an orifice sealing and spray stopping device, conducting hole construction, drilling a designed depth on a bentonite slurry retaining wall, and measuring the deviation condition of a drilled hole by using a high-precision inclinometer; injecting grouting, wherein the in-ground pressure and the mud discharge condition are closely concerned in the injecting grouting process, and the deformation of the existing upper building is monitored; and (5) hole sealing and maintaining, and repeating the steps until the MJS reinforcement body is completely constructed.

S4, reinforcing construction of the underground excavation section by a horizontal freezing method: leveling a field and entering a material field; constructing a freezing pipe; freezing installation and freezing system installation; actively freezing; and monitoring the development conditions of the freezing system and the freezing curtain.

2. The combined construction method of open excavation and freezing underground excavation near an underground communication passage access opening penetrating through a pipe gallery under an existing structure according to claim 1, wherein three-shaft stirring piles with the diameter of 800mm and the interval of 600mm are adopted for foundation reinforcement of the open excavation section, the cement content above the excavation surface of the foundation pit is 7%, the cement content below the bottom of the foundation pit is 18%, and the enclosure structure of the open excavation section consists of single-row drilling meshed piles with the diameter of 1000mm and the interval of 1200 mm.

3. The combined construction method of open excavation and freezing underground excavation of the access opening of the underground communication passage adjacent to the existing structure through the pipe gallery is characterized in that soil between the triaxial mixing pile and the drilling occlusive pile is reinforced by a jet grouting pile, P42.5 ordinary portland cement is added, and the cement dosage is 370 kg/m.

4. The combined construction method of open excavation and freezing underground excavation of the underground communication passage access close to the existing structure underground pipe gallery is characterized in that the triaxial mixing piles and the rotary spraying piles are tested by drilling and coring, open excavation section foundation pit excavation can be performed after the design strength reaches 80%, the mixing piles are maintained for not less than 28 days, the compressive strength of cement soil without side lines is not less than 1.0MPa, and the permeability coefficient is not more than 1E-8 cm/s.

5. The open excavation and freezing underground excavation combined construction method for the underground communication passage access close to the existing structure underpass pipe gallery is characterized in that in the injection grouting process, the underground pressure is controlled to be 1.3-1.6 times of the pressure of an original stratum, the water cement ratio is 1.1, the cement mixing ratio is greater than 45%, the cement slurry pressure is 38-42 MPa, the cement slurry flow is 90-130L/min, the step pitch stroke is 25mm, and the step pitch lifting time is 60 s.

6. The combined open excavation and frozen underground excavation construction method for the underground communication passage access close to the existing structure through the pipe gallery is characterized in that the MJS reinforcement body consists of semicircular piles with the diameter of 2600mm, the bottom of an excavation area of the underground communication passage is provided with two rows, the pile spacing is 1700mm, the row spacing is 700mm, the top and two sides are provided with one row, the pile spacing is 700mm, the pile length is not less than the length of the underground excavation passage, and the levelness of the MJS pile is not more than 1/150.

7. The method of claim 1, wherein the horizontal freezing reinforcement is performed 28 days after the maintenance of the MJS reinforcement at step S3, and the horizontal freezing range is within the MJS reinforcement.

8. The open excavation and freezing underground excavation combined construction method for the underground communication passage access close to the existing structural through-pipe gallery is characterized in that the horizontal freezing method is used for reinforcing the partition according to excavation and guide holes, and the freezing pipes are arranged in a 'field' shape: two rows of freezing pipes are arranged at the bottom and distributed in a quincunx shape, the rest are arranged according to a single row, the freezing pipes are seamless steel pipes with the diameter of phi 89 multiplied by 10mm, the distance is not more than 900mm, temperature measuring holes are arranged in the freezing reinforcement range, and pressure relief holes are arranged in the freezing area.

9. The combined construction method for open excavation and freezing underground excavation of the underground communication passage access opening close to the existing structural underground pipe gallery is characterized in that the temperature of saline water is reduced to below-18 ℃ after being actively frozen for 7 days, the temperature of saline water is reduced to below-24 ℃ after being actively frozen for 15 days, the temperature of saline water is reduced to below-28 ℃ before being excavated, and the temperature difference of saline water in a removing and returning loop is not more than 2 ℃.

10. The method of claim 1, wherein the thickness of the frozen curtain is not less than 2m, the average temperature of the frozen curtain is not more than-10 ℃, and the average temperature at the interface of the frozen curtain and the building envelope is not more than-5 ℃ so that excavation can be carried out in an undercut section.