CN111733839A - A method for strengthening the receiving end of the water-rich sand layer of the shield deep-buried close to the excavation foundation pit - Google Patents

Abstract

The invention discloses a method for reinforcing a receiving end head of a deep-buried shield water-rich sand layer close to an excavated foundation pit, which comprises the following construction steps: step 1: designing an end reinforcement combination form and related parameters according to a traditional end reinforcement method and by combining the condition of a reinforcement area, and designing into an internal MJS construction method pile, an external U-shaped plain ground connecting wall and an internal and external dewatering well; step 2: carrying out internal reinforcement construction by adopting special equipment for the piles in the construction method according to the MJS pile position design; and step 3: adopting a trenching machine to carry out MJS reinforcement body peripheral plain ground wall connection construction; and 4, step 4: reinforcing construction is carried out on weak positions of the peripheral plain ground connecting wall by adopting special equipment for the construction method piles; and 5: and adopting a reverse circulation drill to carry out construction of the dewatering well inside and outside the plain ground connecting wall. The invention improves the reinforcement quality on the premise of ensuring synchronous and safe excavation of the near deep foundation pit, and has the advantages of higher construction efficiency, strong adaptability, civilization and environmental protection.

Description

A method for strengthening the receiving end of the water-rich sand layer of the shield buried close to the excavation foundation pit

technical field

The invention relates to the technical field of shield tunnel construction, in particular to a method for reinforcing a receiving end of a shield tunnel with water-rich sand layers that is deeply buried next to an excavation foundation pit.

Background technique

With the rapid development of infrastructure construction in my country, shield construction has been widely used in the construction of urban subways and sewage tunnels due to its safety and efficiency. Shield receiving is one of the most important risk points in the process of shield construction, and the key to controlling this risk is to choose an appropriate reinforcement scheme for the receiving end of the shield.

The traditional end reinforcement methods, such as high-pressure rotary jetting piles, CSM mixing walls, plain connecting walls and dewatering wells used alone or in combination with each other, have their own limitations, that is, it is difficult to ensure the safety of synchronous excavation of foundation pits. It is also difficult to achieve the expected reinforcement effect in the deep water-rich sand layer.

SUMMARY OF THE INVENTION

In order to overcome the technical defects that the traditional end reinforcement method in the prior art is difficult to ensure the safety of synchronous excavation of the foundation pit, and it is difficult to achieve the expected reinforcement effect in the large-depth water-rich sand layer, the present invention provides a method for excavating the foundation pit next to the foundation pit. The reinforcement method of the receiving end of the water-rich sand layer of the deep-buried shield tunnel can be adjusted in time according to the site and shaft conditions, and is especially suitable for the reinforcement of the end under adverse geological conditions such as ultra-deep foundation pits, ultra-thick sand layers, and ultra-high confined water. The construction solves the above technical problems.

The present invention achieves the above object through the following technical solutions, a method for reinforcing the receiving end of the water-rich sand layer of a shield deep buried in close proximity to the excavation foundation pit, comprising the following construction steps:

S1: Design of the end reinforcement combination form and related parameters:

According to the traditional reinforcement method and combined with the situation of the reinforcement area, the end reinforcement combination form and related parameters are designed. The design reinforcement concept is to focus on double-layer water plugging, supplemented by internal and external precipitation, that is, internal MJS construction method piles are used for inner layer plugging. For water, the U-shaped plain-ground connecting wall is used as the outer layer for water blocking, and an internal draining and dewatering well is set in the middle of the internal MJS construction method pile and the U-shaped plain-ground connecting wall, and an external dewatering well is set on the periphery of the U-shaped plain-ground connecting wall. ;

S2: Use special equipment for construction method piles to carry out the construction of internal MJS construction method pile reinforcement:

Adopt hole-guiding machine, MJS construction method host and equipped with cement tank, high pressure pump, clean water pump and excavator to carry out construction method pile construction reasonably according to the internal MJS construction method pile distribution. The construction method pile drill bit is drilled from the casing to the bottom → the casing is pulled back in sections and sprayed to the top of the pile;

S3: Use the slotting machine to construct the peripheral U-shaped plain wall:

The slotting machine is equipped with a mud system, a locking pipe and a conduit to perform the amplitude jumping construction according to the framing conditions of the plain wall;

S4: The reinforcement construction of MJS construction method piles at the joints of the plain wall is carried out on the periphery of the weak part of the U-shaped plain-ground connecting wall:

The MJS construction method piles at the joints of the plain wall outside the U-shaped plain-ground connecting wall are partially reinforced, and the construction steps are the same as those of the internal MJS construction method piles;

S5: Reverse circulation drilling is used for the construction of U-shaped plain ground wall and inner and outer dewatering wells:

According to the geological conditions, the reverse circulation drill with rock penetration ability is used to construct the dewatering well in the reinforcement area.

The above-mentioned reinforcement method for the receiving end of the shield buried in the water-rich sand layer close to the excavation foundation pit, the pile-forming reinforcement principle of the internal MJS construction method pile is compared with the traditional reinforcement methods such as high-pressure rotary jet piles and CSM mixing walls. The big difference is that the high-pressure jetting pile and the CSM mixing wall are mixed and reinforced by mixing the soil and injecting cement slurry, while the MJS construction method first passes the lead hole to the bottom of the pile, and then sets the casing, and the construction method pile drill bit from the casing. After drilling down to the bottom in the pipe, it is lifted up in sections and sprayed with high-pressure cement slurry to cut the surrounding soil; the forced slurry discharge in the hole and the monitoring of the pressure in the ground are realized. The reasonable control of sludge discharge and pressure in the ground also reduces the possibility of surface deformation during construction and greatly reduces the impact on the environment.

In the above-mentioned method for strengthening the receiving end of the shield buried in the water-rich sand layer of the shield buried close to the excavation foundation pit, the U-shaped plain ground connecting wall is used for joint treatment with a locking pipe, and the pipe wall is closely attached to the groove wall to prevent it. Concrete pour and flow around.

In the above-mentioned method for strengthening the receiving end of a shield buried in a water-rich sand layer close to the excavation foundation pit, the weak joint of the U-shaped plain connecting wall is subjected to secondary reinforcement treatment to improve the water-retaining capacity of the plain wall outside the reinforcement area. , to enhance the reinforcement effect of the peripheral reinforcement.

In the above-mentioned method for strengthening the receiving end of a shielded water-rich sand layer that is deeply buried next to the excavation foundation pit, the dewatering wells are distributed on the inner and outer sides of the U-shaped plain ground connecting wall, and the confined water enters the U-shaped plain ground through the joint. When inside the connecting wall, the external dewatering wells are pumped and drained to lower the local water head elevation at the joints and reduce the amount of groundwater entering the interior of the U-shaped plain-ground connecting wall. The groundwater entering the U-shaped plain wall can be collected and drained in time, thereby improving the overall quality of the reinforcement area.

In the above-mentioned method for strengthening the receiving end of the shield tunnel with water-rich sand layers that are deeply buried in the excavation foundation pit, the design value of the pile diameter of the internal MJS construction method pile is 1.2 m, and the internal MJS construction method pile and the U-shaped plain ground connecting wall bottom mark. The height is more than 3.0m lower than the bottom elevation of the shield tunnel, and the bottom elevation of the dewatering well is the same as the bottom elevation of the shield tunnel.

In general, compared with the prior art, the following beneficial effects can be achieved by the above technical solutions conceived by the present invention:

1. The end reinforcement method of the present invention combines the MJS process with the tunnel end receiving reinforcement for the first time, and further optimizes the combination form of the traditional high-pressure rotary jet pile + plain ground wall + dewatering well, and innovatively proposes the MJS construction method pile +U-shaped plain ground connecting wall + combined end reinforcement method of internal and external dewatering wells, abandoning the traditional single water stop reinforcement concept, and forming a new reinforcement concept based on double-layer water blocking and supplemented by internal and external precipitation;

2. The MJS + plain wall + dewatering well combined reinforcement construction method can get rid of the limitations of traditional reinforcement methods, and can be adjusted in time according to the site and shaft conditions, especially suitable for ultra-deep foundation pits, ultra-thick sand layers, ultra-high confined water End reinforcement construction under adverse geological conditions.

3. The end reinforcement method of the present invention is further deepened on the basis of the simple traditional reinforcement method, which is mainly based on blockage reduction and supplemented by water reduction. The double water-proof wall and MJS reinforcement and combined with the internal and external dewatering wells for dewatering can achieve the effect of good receiving environment. The new technology MJS construction method can adjust the pressure in the ground, and its deep pile diameter and quality are better than high-pressure rotary jet piles.

4. The end reinforcement method of the present invention is safe, green and environmentally friendly. The MJS construction method pile in this construction method can control the pressure in the ground by adjusting the amount of forced slurry discharge, effectively controlling the overflow of mud and surface deformation. When the shaft is excavated synchronously, First, the internal MJS construction method piles are constructed to stabilize the stratum at the end, and then the external U-shaped plain wall is constructed to ensure the safety of synchronous excavation of the foundation pit.

Description of drawings

The specific embodiments of the present invention will be described in further detail below in conjunction with the accompanying drawings, wherein:

Fig. 1 is a construction flow chart of a method for reinforcing the receiving end of the water-rich sand layer of a shield tunnel deep buried in close proximity to the excavation foundation pit of the present invention;

2 is a schematic plan view of end head reinforcement in an embodiment of the present invention;

Fig. 3 is the cross-sectional schematic diagram of the end head reinforcement in the embodiment of the present invention;

4 is a schematic diagram of the water-stop effect of end reinforcement in an embodiment of the present invention;

In the picture: 1-Internal MJS construction method pile, 2-MJS construction method pile at the joint of plain wall, 3-U-shaped plain ground connecting wall, 4-Internal drainage and dewatering well, 5-External dewatering well, 6-9# shaft, 7 - Shield Tunnel.

Detailed ways

As shown in Figure 1, it is a construction flow chart of a method for reinforcing the receiving end of the water-rich sand layer of a shield that is deeply buried next to the excavation foundation pit of the present invention, and the end reinforcing method comprises the following construction steps:

Step 1: Design of the end reinforcement combination form and related parameters:

According to the traditional reinforcement method and combined with the situation of the reinforcement area, the end reinforcement combination form and related parameters are designed. The design reinforcement concept is to focus on double-layer water blocking, supplemented by internal and external precipitation, that is, using A1200@1000mm internal MJS construction method pile 1 For inner layer water plugging, the 800mm U-shaped plain ground connecting wall 3 is used as the outer layer water plugging, and an internal draining and dewatering well 4 is set in the middle position between the internal MJS construction method pile 1 and the U-shaped plain ground connecting wall 3, and the U-shaped plain ground connecting wall 3 An external dewatering well 5 is arranged on the periphery of the wall 3, as shown in Figures 2 and 3, which are a schematic plan view and a schematic cross-sectional view of the end reinforcement.

Step 2: Use the special equipment for construction method piles to carry out the construction of the internal MJS construction method pile 1 reinforcement:

Adopt hole-guiding machine, MJS construction method host and equipped with cement tank, high-pressure pump, clean water pump and excavator to reasonably carry out construction method pile construction according to the distribution of internal MJS construction method pile 1. The construction steps are mainly: drilling down the pilot bit to form a hole → casing placement →The drill bit of the construction method is drilled from the casing to the bottom →the casing is pulled back in sections and sprayed to the top of the pile.

Step 3: Use the slotting machine to construct the peripheral U-shaped plain wall 3:

The slotting machine is equipped with a mud system, a locking pipe and a conduit to perform amplitude jumping construction according to the sizing of the plain wall. The construction steps are mainly: guide wall production → mud configuration → slotting machine forming a slot → locking pipe hanging → concrete pouring → Pull out the locking tube.

Step 4: Carry out the reinforcement construction of the MJS method pile 2 at the joint of the plain wall at the periphery of the weak part of the U-shaped plain wall 3:

Perform local reinforcement treatment on the MJS construction method pile 2 at the joint of the plain wall outside the joint position of the U-shaped plain-ground connecting wall 3, especially the connection between the U-shaped plain-ground connecting wall 3 and the 9# shaft 6 crown beam. The construction steps are the same as the internal MJS Construction method pile 1 is the same.

Step 5: Use reverse circulation drilling to construct the inner and outer dewatering wells of U-shaped plain connecting wall 3:

According to the geological conditions, the reverse circulation drill with rock-penetrating ability is used to construct the dewatering well in the reinforced area. The main construction steps are: drilling into the hole → filling the filter material in the downhole pipe → water stop and sealing the hole and washing the well → pumping down the water.

The end reinforcement method of the present invention is further deepened on the basis of the simple traditional reinforcement method, which is mainly based on blocking reduction and supplemented by reduction, and further deepens into a reinforcement method based on double-layer water blocking and supplemented by internal and external precipitation. The peripheral U-shaped plain ground The double water barrier of connecting wall 3 and MJS reinforcement and combined with the internal and external dewatering wells for dewatering can achieve the effect of good receiving environment. The new technology MJS construction method can adjust the pressure in the ground, and its deep pile diameter and quality are better than high-pressure rotary jet piles , as shown in FIG. 4 , which is a schematic diagram of the water-stop effect of the end reinforcement of the present invention.

MJS construction method piles can control the pressure in the ground by adjusting the amount of forced slurry discharge, effectively controlling the mud overflow and surface deformation. When the 9# shaft 6 is excavated simultaneously, the internal MJS construction method pile 1 is constructed first to stabilize the stratum at the end, and then the external U-shaped pile is constructed. The ground is connected to the wall 3 to ensure the safety of synchronous excavation of the foundation pit.

Those skilled in the art can easily understand that the above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, etc., All should be included within the protection scope of the present invention.

Claims (4)

1. a method for receiving end reinforcements for the deep buried shield water-rich sand layers of excavated foundation pits is characterized in that, this end reinforcement method comprises the following construction steps: S1: Design of the end reinforcement combination form and related parameters: According to the traditional reinforcement method and combined with the situation of the reinforcement area, the end reinforcement combination form and related parameters are designed. The design reinforcement concept is to focus on double-layer water plugging, supplemented by internal and external precipitation, that is, using internal MJS construction method piles (1). For water blocking in the inner layer, the U-shaped plain-ground connecting wall (3) is used as the outer water-blocking, and an internal drainage and dewatering well (4) is set in the middle of the inner MJS construction method pile (1) and the U-shaped plain-ground connecting wall (3). ), and an external dewatering well (5) is arranged on the periphery of the U-shaped plain connecting wall (3); S2: Use special equipment for construction method piles to carry out the construction of internal MJS construction method piles (1) reinforcement: Adopt hole-guiding machine, MJS construction method host and equipped with cement tank, high-pressure pump, clean water pump and excavator to reasonably carry out construction method pile construction according to the distribution of internal MJS construction method piles (1). Pipe placement → construction method pile drill bit is drilled from the casing to the bottom → the casing is pulled back in sections and sprayed to the top of the pile; S3: The construction of the peripheral U-shaped plain ground wall (3) is carried out by using a slotting machine: The slotting machine is equipped with a mud system, a locking pipe and a conduit to perform the amplitude jumping construction according to the framing conditions of the plain wall; S4: Carry out the reinforcement construction of the MJS method pile (2) at the joint of the plain wall at the periphery of the weak part of the U-shaped plain-ground connecting wall (3): The MJS construction method pile (2) at the joint of the plain wall outside the joint position of the U-shaped plain ground connecting wall (3) is partially reinforced, and the construction steps are the same as the internal MJS construction method pile (1); S5: Use reverse circulation drilling to carry out the construction of U-shaped plain ground connecting walls (3) Construction of internal and external dewatering wells: According to the geological conditions, the reverse circulation drill with rock penetration ability is used to construct the dewatering well in the reinforcement area. 2 . The method for strengthening the receiving end of the water-rich sand layer of a shield deep buried close to the excavation foundation pit according to claim 1 , wherein the pile diameter design of the internal MJS construction method pile ( 1 ) in the step S1 The value is 1.2m, the bottom elevation of the internal MJS construction method pile (1) and U-shaped plain connecting wall (3) is lower than the bottom elevation of the shield tunnel (7) by more than 3.0m, and the internal dewatering well (4) and the external dewatering well ( The bottom elevation of 5) is flush with the bottom elevation of shield tunnel (7). 3. The method for strengthening the receiving end of the water-rich sand layer of a shield deep-buried close to the excavation foundation pit according to claim 1, wherein the construction of the U-shaped plain ground connecting wall (3) in the step S3, The framing position is seamed with a locking pipe, and the pipe wall is closely attached to the groove wall. 4. the method for reinforcing the receiving end of the water-rich sand layer of a shield deep-buried close to the excavation foundation pit according to claim 1, characterized in that, in the dewatering well construction in the step S5, when the confined water is connected by When the joint enters the interior of the U-shaped plain-ground connecting wall (3), the external dewatering well (5) is pumped and drained to lower the local water head elevation at the joint and reduce the amount of groundwater entering the interior of the U-shaped plain-ground connecting wall (3). An internal draining and dewatering well (4) is arranged between the plain-ground connecting wall (3) and the reinforcement of the internal MJS construction method pile (1), so as to collect and drain the groundwater entering the U-shaped plain-ground connecting wall (3) in time, thereby enhancing the reinforcement the overall quality of the district.

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