A shield end shaft reinforcement structure capable of absorbing extrusion deformation and a construction method thereof

Abstract

The present invention provides a shield end shaft reinforcement structure capable of absorbing extrusion deformation and a construction method thereof, the reinforcement structure comprising a first vertical reinforcement layer, a second vertical reinforcement layer coated outside the first vertical reinforcement layer, and a rotary jet pile reinforcement layer filled between the first vertical reinforcement layer, the second vertical reinforcement layer and the end shaft side wall; the first vertical reinforcement layer covers the tunnel construction area and the edges on all sides extend outward beyond the tunnel construction area. The reinforcement structure provided by the present invention is formed by a first vertical reinforcement layer of solidified soil mixed with foam having extremely strong impermeability and deformation absorption performance, and a second vertical reinforcement layer of cement solidified soil having excellent impermeability and whole plate performance. Compared with the traditional single cement soil reinforcement structure, it has a good ability to absorb extrusion deformation, avoids the generation of a large number of through cracks in the reinforcement area when the shield passes, reduces the occurrence of water and sand gushing in the starting and receiving stages of the shield, and greatly improves the construction safety.

Description

Technical Field

[0001] The invention relates to the technical field of civil engineering materials and construction, and in particular to a shield end shaft reinforcement structure capable of absorbing extrusion deformation and a construction method thereof. Background Art

[0002] During the shield construction process, the shield machine's starting stage (the shield body completely enters the soil from the starting well and is pushed forward by the reaction frame) and the receiving stage (the shield body is completely pushed out of the soil and enters the receiving well) are two construction stages with major safety risks. One of the main safety risk factors is that the shield body is in the middle of the tunnel portal, and the tunnel portal is not closed. Groundwater and quicksand can easily flow into (or pour into) the starting well and the receiving well through the gap between the shield body and the tunnel portal, causing the soil outside the side wall of the end well to become unstable, leading to collapse and pipe burst safety accidents. In order to reduce safety risks, the outer wall reinforcement technology of the starting and receiving end end wells is often used, and the commonly used reinforcement method is cement-cured soil waterstop wall.

[0003] Engineering applications have shown that cement-solidified soil water-stop walls effectively reduce the safety risks of shield starting and receiving. However, since cement soil exhibits extremely brittle failure characteristics after solidification and has a weak ability to absorb deformation under compression, the soil in the reinforced area is often squeezed and rapidly cracked when the shield passes through, resulting in through cracks extending to the unreinforced area, providing an original channel for the flow of groundwater and quicksand to the working face, greatly reducing the water-stopping effect of the reinforced area. The resulting rescue work in the starting and receiving stages frequently occurred, becoming an unavoidable technical problem in shield construction at the time. Summary of the invention

[0004] The purpose of the present invention is to solve the above-mentioned deficiencies and provide a shield end shaft reinforcement structure capable of absorbing extrusion deformation and a construction method thereof.

[0005] To achieve the above object, according to one aspect of the present invention, there is provided a shield end well reinforcement structure capable of absorbing extrusion deformation, which is arranged at a position close to the end well and comprises a first vertical reinforcement layer, a second vertical reinforcement layer covering the first vertical reinforcement layer, and a jet grouting pile reinforcement layer filled between the first vertical reinforcement layer, the second vertical reinforcement layer and the end well side wall;

[0006] The first vertical reinforcement layer is made of solidified soil mixed with foam, and the second vertical reinforcement layer is made of cement solidified soil. The first vertical reinforcement layer covers the tunnel construction area and its edges extend outward beyond the tunnel construction area.

[0007] Furthermore, the axial distribution area of ​​the first vertical reinforcement layer is from 0.65m away from the side wall of the end well to 10-15m along the tunnel direction, and the circumferential distribution area of ​​the first vertical reinforcement layer is from the center of the tunnel construction area to 1m outside the tunnel contour line. This design is convenient for workers to carry out construction, and it has been verified that the reinforcement effect is reliable.

[0008] Furthermore, the axial distribution area of ​​the second vertical reinforcement layer is from 0.65m away from the side wall of the end well to 10-15m along the tunnel direction, and the circumferential distribution area of ​​the second vertical reinforcement layer is from 1m outside the tunnel contour line to 3-5m outside the tunnel contour line. This design is convenient for workers to carry out construction, and it has been verified that the reinforcement effect is reliable.

[0009] Furthermore, the axial distribution area of ​​the jet grouting reinforcement layer is within the range of 0.65m from the side wall of the end well to the extension along the tunnel direction, and the circumferential distribution area of ​​the jet grouting reinforcement layer is within the range of 5m from the center of the tunnel construction area to the tunnel contour line. This design is convenient for workers to carry out construction, and it has been verified that the reinforcement effect is reliable.

[0010] Furthermore, the solidified soil mixed with foam is prepared by mixing foam, a solidifying agent and in-situ soil, and the foam is added by volume, with a ratio of 10% to 15% of the volume of the in-situ soil. With this design, the volume of foam added is small, which is based on reducing the volume expansion of the soil caused by the foam. A large number of tests have shown that the volume expansion of the soil caused by the above amount of foam added is extremely small.

[0011] Furthermore, the characteristics of the stabilized soil mixed with foam at 28 days are as follows: the unconfined compressive strength is not less than 1.2 MPa, the permeability coefficient is not greater than 1.0×10 -7 cm / s, wet density not more than 1300kg / m 3 This design ensures that the first vertical reinforcement layer has a stable structure and has the ability to quickly absorb the extrusion deformation of the shield body. It has a simple structure and is stable and reliable.

[0012] Furthermore, the foam is made by mechanical foaming of anionic foaming agent, the foam diameter is 30-400 μm, the foam half-life is not less than 30 min, and the foam wet density is not more than 19 kg / m 3 With this design, the foam sealing holes stably and evenly distributed in the solidified soil mixed with foam have the ability to absorb the extrusion deformation of the shield machine. The low amount of foam makes the solidified soil have higher mechanical strength at the same time, meeting the structural bearing requirements.

[0013] Furthermore, the curing agent is selected from one of cement, inorganic soil curing agent and composite soil curing agent. This design ensures the curing performance, thereby ensuring the structural stability of the first vertical reinforcement layer.

[0014] Furthermore, the cement-solidified soil used in the second vertical reinforcement layer is prepared by mixing cement slurry and in-situ soil, and the water-cement ratio of the cement slurry is 0.8 to 1.5. In this way, the strength of the second vertical reinforcement layer is improved by designing a suitable ratio.

[0015] Furthermore, the characteristics of the cement-solidified soil at 28 days of age are as follows: the unconfined compressive strength is not less than 1.0 MPa, the permeability coefficient is not greater than 1.0×10 -7 This design ensures the structural stability of the second vertical reinforcement layer and the water-stopping effect, reduces the occurrence of water and sand gushing during the shield starting and receiving stages, and greatly improves the construction safety during the shield starting and receiving stages.

[0016] Furthermore, the characteristics of the jet grouting pile reinforcement layer at 28 days after hardening are as follows: the unconfined compressive strength is not less than 2.5 MPa, the permeability coefficient is not greater than 1.0×10 -7 cm / s. This design ensures the performance of the jet grouting piles and improves the stability of the structure.

[0017] According to another aspect of the present invention, a construction method for a shield end shaft reinforcement structure capable of absorbing extrusion deformation is also provided, comprising the following steps:

[0018] First, the end well side wall is constructed, then the first vertical reinforcement layer and the second vertical reinforcement layer are constructed at the outer end of the end well side wall, and finally the rotary jet pile reinforcement layer is constructed. Each area is constructed from bottom to top;

[0019] When constructing the first vertical reinforcement layer and the second vertical reinforcement layer, first construct the lower part of the second vertical reinforcement layer, then construct the first vertical reinforcement layer to the designed elevation, and finally construct the upper part of the second vertical reinforcement layer.

[0020] The main technical principles of the present invention are:

[0021] (1) The present invention adopts a structure in which the second vertical reinforcement layer wraps the first vertical reinforcement layer. The second vertical reinforcement layer is formed by cement-solidified soil with excellent impermeability and whole plate performance, and the first vertical reinforcement layer is formed by solidified soil mixed with foam with extremely strong impermeability and deformation absorption performance, forming a composite reinforcement structure of the shield end well in which a solidified soil water-stopping layer wraps a foam solidified soil extrusion deformation absorption layer. When the shield machine passes through the reinforced structure, the extrusion deformation of the shield machine is absorbed by the first vertical reinforcement layer without generating a large number of through cracks, thereby ensuring the stability of the second vertical reinforcement layer and exerting an excellent water-stopping effect. The solidified soil mixed with foam and the cement-solidified soil used in the composite structure have similar material performances, good compatibility, no obvious transition interface between the structures, no weak links inside the structure, and good integrity;

[0022] (2) The present invention specifies that the foam is added by volume, and the proportion is 10% to 15% of the original soil volume. The small volume of foam added is based on reducing the volume expansion of the soil caused by the foam. A large number of tests have shown that the foam added in the above amount causes very little volume expansion of the soil, which can be ignored in engineering. The foam sealing holes stably and evenly distributed in the solidified soil mixed with the foam have the ability to absorb the extrusion deformation of the shield machine. The low amount of foam added makes the solidified soil have a higher mechanical strength and meet the structural bearing requirements.

[0023] (3) The diameter of the foam after physical foaming of the anionic foaming agent used in the present invention is 30 to 400 μm, which is a small diameter foam. The fine foam is evenly and stably dispersed in the solidified soil mixed with foam. After the solidified soil hardens, a closed honeycomb space is formed. Each air bag exists independently without forming original through cracks. The solidified soil mixed with foam exhibits good mechanical strength and excellent anti-seepage performance, meeting the triple functional requirements of bearing, absorbing extrusion deformation and water stopping.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The present invention combines the reinforcement material and the reinforcement structure innovatively, adopts the structure of the second vertical reinforcement layer wrapping the first vertical reinforcement layer, the second vertical reinforcement layer is formed by cement-solidified soil with excellent impermeability and whole plate performance, and the first vertical reinforcement layer is formed by solidified soil mixed with foam with extremely strong impermeability and deformation absorption performance. When the shield body passes through, the first vertical reinforcement layer has the ability to quickly absorb the extrusion deformation of the shield body without forming through cracks, and the second vertical reinforcement layer has a good water-stopping effect, which reduces the occurrence of water and sand gushing in the shield starting and receiving stages, and greatly improves the construction safety of the shield starting and receiving stages;

[0026] (2) The new structure provided by the present invention does not require any new or complex construction equipment. A composite reinforced new structure that absorbs extrusion deformation can be constructed according to normal construction technology. The construction technology of the new structure is simple, mature, and highly practical.

[0027] (3) The new composite reinforcement structure for absorbing extrusion deformation provided by the present invention is suitable for reinforcing the end of geological shields in water-rich silt, clay and fine sand layers. It has a wide range of geological applications, and can be used in particular to solve the technical problems of water and sand gushing from the tunnel gate during the starting and receiving stages of shields in water-rich strata, thereby ensuring the safety of shield construction in water-rich strata. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of a top view of the structure of an embodiment of the present invention.

[0029] Figure 2 It is a schematic diagram of a side cross-sectional structure of an embodiment of the present invention.

[0030] In the figure: 1. Tunnel outline; 2. First vertical reinforcement layer; 3. Second vertical reinforcement layer; 4. Jet-grouting pile reinforcement layer; 5. Side wall of end well; L1 - outward extension along the tunnel direction; L2 - outward extension length of tunnel outline. DETAILED DESCRIPTION

[0031] The present invention is further described below in conjunction with examples. The implementation methods of the following examples, unless otherwise specified, are all conventional reagents and conventional methods known in the art.

[0032] like Figure 1 and Figure 2 shown.

[0033] The shield end well reinforcement structure capable of absorbing extrusion deformation of the present invention is arranged at a position close to the end well, and comprises a first vertical reinforcement layer 2, a second vertical reinforcement layer 3 coated outside the first vertical reinforcement layer 2, and a jet-jet pile reinforcement layer 4 filled between the first vertical reinforcement layer 2, the second vertical reinforcement layer 3 and the end well side wall 5;

[0034] The first vertical reinforcement layer 2 is made of solidified soil mixed with foam, and the second vertical reinforcement layer 3 is made of cement solidified soil. The first vertical reinforcement layer 2 covers the tunnel construction area and its edges extend outward beyond the tunnel construction area.

[0035] The axial distribution area of ​​the first vertical reinforcement layer 2 is from 0.65m away from the side wall of the end shaft to 10-15m along the tunnel direction, and the circumferential distribution area of ​​the first vertical reinforcement layer 2 is from the center of the tunnel construction area to the range of 1m outward from the tunnel contour line 1.

[0036] The axial distribution area of ​​the second vertical reinforcement layer 3 is from 0.65m away from the side wall of the end shaft to 10-15m extending along the tunnel direction, and the circumferential distribution area of ​​the second vertical reinforcement layer 3 is from 1m outside the tunnel contour line 1 to 3-5m outside the tunnel contour line 1.

[0037] The axial distribution area of ​​the jet grouting reinforcement layer 4 is within a range of 0.65 m from the end shaft side wall 5 to the tunnel direction, and the circumferential distribution area of ​​the jet grouting reinforcement layer 4 is within a range of 5 m from the center of the tunnel construction area to the tunnel contour line 1.

[0038] The construction method of the shield end shaft reinforcement structure capable of absorbing extrusion deformation of the present invention comprises the following steps:

[0039] First, the end well side wall 5 is constructed, then the first vertical reinforcement layer 2 and the second vertical reinforcement layer 3 are constructed at the outer end of the end well side wall 5, and finally the rotary jet pile reinforcement layer 4 is constructed. Each area is constructed from bottom to top;

[0040] When constructing the first vertical reinforcement layer 2 and the second vertical reinforcement layer 3 at the outer end, first construct the lower part of the second vertical reinforcement layer 3, then construct the first vertical reinforcement layer 2 to the designed elevation, and finally construct the upper part of the second vertical reinforcement layer 3.

[0041] Three embodiments are provided below to illustrate the present invention in detail:

[0042] Example 1

[0043] This embodiment is the reinforcement of the shield starting end well of a certain section of Hangzhou Metro. The strata in the reinforcement area are clay, silty clay, silty clay, silty clay with silty clay, and silty clay with fine sand from top to bottom. Hydrological exploration data show that this area belongs to a water-rich stratum. The reinforcement structure adopts the shield end well reinforcement structure that can absorb extrusion deformation of the present invention:

[0044] Among them, the axial distribution area of ​​the first vertical reinforcement layer 2 is from 0.65m to the side wall of the end shaft to 15m along the tunnel direction, and the circumferential distribution area is from the center of the tunnel construction area to 1m outside the tunnel contour line. The range is solidified soil mixed with foam prepared by a three-axis mixing process.

[0045] The solidified soil mixed with foam is prepared by mixing foam, a solidifying agent and in-situ soil. The foam is added by volume, and the proportion is 10% of the volume of the in-situ soil. The foam is mechanically foamed by an anionic foaming agent (purchased from Wuhan Zhenxuan Chemical Co., Ltd., the same below). The foam diameter is 30 μm, the foam half-life is 35 min, and the foam wet density is 18 kg / m 3 The curing agent is an inorganic soil curing agent (purchased from Zhongke Shenglian (Beijing) Environmental Protection Technology Co., Ltd.).

[0046] The characteristics of the 28-day-old solidified soil mixed with foam in this embodiment are as follows: unconfined compressive strength is 1.3 MPa, permeability coefficient is not greater than 7.2×10 -8 cm / s, wet density is 1250kg / m3 .

[0047] Among them, the axial distribution area of ​​the second vertical reinforcement layer 3 is from 0.65m away from the side wall of the end shaft to 15m along the tunnel direction, and the circumferential distribution area is from 1m outside the tunnel contour line 1 to 3m outside the tunnel contour line 1. The range is cement-solidified soil prepared by the three-axis mixing process.

[0048] The cement-solidified soil is made by mixing cement slurry and in-situ soil, with a cement content of 300kg / m 3 The water-cement ratio of cement paste is 0.8, and the cement is P·O42.5 grade cement.

[0049] The characteristics of the cement-stabilized soil at 28 days of age in this example are as follows: unconfined compressive strength 1.0 MPa, permeability coefficient 8.7×10 -8 cm / s.

[0050] Among them, the axial distribution area of ​​the jet grouting pile reinforcement layer 4 is within the range of 0.65m from the side wall of the end well to the extension along the tunnel direction, and the circumferential distribution area is within the range of 5m from the center of the tunnel construction area to the tunnel contour line 1. The range is the cement slurry jet grouting piles prepared by the high-pressure jet grouting process.

[0051] The characteristics of the jet grouting pile reinforcement layer after hardening for 28 days are as follows: unconfined compressive strength is 2.7 MPa, permeability coefficient is 5.4×10 -8 cm / s.

[0052] Example 2

[0053] This embodiment is the reinforcement of the shield starting end well of a certain section of Suzhou Metro. The strata in the reinforcement area are silt-sand layer, silt-sand layer, silty clay layer, and clay layer from top to bottom. The exploration data shows that this area belongs to water-rich geology and has obvious seasonal characteristics. The reinforcement structure adopts the shield end well reinforcement structure of the present invention that can absorb extrusion deformation:

[0054] Among them, the axial distribution area of ​​the first vertical reinforcement layer 2 is from 0.65m to the side wall of the end shaft to 10m along the tunnel direction, and the circumferential distribution area is from the center of the tunnel construction area to 1m outside the tunnel contour line. The range is solidified soil mixed with foam prepared by the three-axis mixing process.

[0055] The solidified soil mixed with foam is made by mixing foam, curing agent and in-situ soil. The foam is added by volume, and the proportion is 15% of the volume of the in-situ soil. The foam is made by mechanical foaming of anionic foaming agent. The foam diameter is 50-300 μm, the foam half-life is 35 min, and the foam wet density is 18 kg / m 3The curing agent is a composite soil curing agent (purchased from Zhongke Shenglian (Beijing) Environmental Protection Technology Co., Ltd.).

[0056] The characteristics of the 28-day-old solidified soil mixed with foam in this embodiment are as follows: unconfined compressive strength is 1.4 MPa, permeability coefficient is not more than 6.3×10 -8 cm / s, wet density is 1200kg / m 3 .

[0057] Among them, the axial distribution area of ​​the second vertical reinforcement layer 3 is from 0.65m to the side wall of the end shaft to 10m along the tunnel direction, and the circumferential distribution area is from 1m outside the tunnel contour line 1 to 5m outside the tunnel contour line 1. The range is cement-solidified soil prepared by the three-axis mixing process.

[0058] The cement-solidified soil is made by mixing cement slurry and in-situ soil, with a cement content of 200 kg / m 3 The water-cement ratio of cement paste is 1.5, and the cement is P·O42.5 grade cement.

[0059] The characteristics of the cement-stabilized soil at 28 days of age in this example are as follows: unconfined compressive strength 1.1 MPa, permeability coefficient 9.2×10 -8 cm / s.

[0060] Among them, the axial distribution area of ​​the jet grouting pile reinforcement layer 4 is within the range of 0.65m from the side wall of the end well to the extension along the tunnel direction, and the circumferential distribution area is within the range of 5m from the center of the tunnel construction area to the tunnel contour line 1. The range is the cement slurry jet grouting piles prepared by the high-pressure jet grouting process.

[0061] The characteristics of the jet grouting pile reinforcement layer after hardening for 28 days are as follows: unconfined compressive strength is 2.9 MPa, permeability coefficient is 8.2×10 -8 cm / s.

[0062] Example 3

[0063] This embodiment is the reinforcement of the receiving end well of a certain section of the Fuzhou Metro. The strata in the reinforcement area are silt, silty clay and medium sand layers from top to bottom. The reinforcement structure adopts the shield end well reinforcement structure that can absorb extrusion deformation of the present invention:

[0064] Among them, the axial distribution area of ​​the first vertical reinforcement layer 2 is from 0.65m to the side wall of the end shaft to 10m along the tunnel direction, and the circumferential distribution area is from the center of the tunnel construction area to 1m outside the tunnel contour line. The range is solidified soil mixed with foam prepared by the three-axis mixing process.

[0065] The solidified soil mixed with foam is made by mixing foam, curing agent and in-situ soil. The foam is added by volume, and the proportion is 12% of the volume of the in-situ soil. The foam is made by mechanical foaming of anionic foaming agent. The foam diameter is 30-400 μm, the foam half-life is 40 minutes, and the foam wet density is 18 kg / m 3 , the curing agent is cement.

[0066] The characteristics of the stabilized soil mixed with foam at 28 days of age in this embodiment are as follows: unconfined compressive strength is 1.3 MPa, permeability coefficient is not greater than 7.4×10 -8 cm / s, wet density is 1230kg / m 3 .

[0067] Among them, the axial distribution area of ​​the second vertical reinforcement layer 3 is from 0.65m to the side wall of the end shaft to 10m along the tunnel direction, and the circumferential distribution area is from 1m outside the tunnel contour line 1 to 5m outside the tunnel contour line 1. The range is cement-solidified soil prepared by the three-axis mixing process.

[0068] The cement-solidified soil is made by mixing cement slurry and in-situ soil, with a cement content of 100 kg / m 3 , the water-cement ratio of cement paste is 1.0, and the cement is P·O42.5 grade cement.

[0069] The characteristics of the cement-stabilized soil at 28 days of age in this example are as follows: unconfined compressive strength 1.3 MPa, permeability coefficient 8.2×10 -8 cm / s.

[0070] Among them, the axial distribution area of ​​the jet grouting pile reinforcement layer 4 is within the range of 0.65m from the side wall of the end well to the extension along the tunnel direction, and the circumferential distribution area is within the range of 5m from the center of the tunnel construction area to the tunnel contour line 1. The range is the cement slurry jet grouting piles prepared by the high-pressure jet grouting process.

[0071] The characteristics of the jet grouting pile reinforcement layer after hardening for 28 days are as follows: unconfined compressive strength is 2.5 MPa, permeability coefficient is 6.9×10 -8 cm / s.

[0072] The strata in Examples 1-3 all showed a water-rich state, but during the shield tunneling start-up or receiving construction phase, no large amount of water and sand gushing was observed at the tunnel entrance, no obvious settlement was observed around the side walls of the end shaft, no collapse occurred, and the surrounding buildings were stable and without deformation. Observations showed that the water-stopping effect of the composite reinforcement structure was significantly better than that of the traditional single solidified soil reinforcement structure.

[0073] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention.

Claims

1. A shield end shaft reinforcement structure capable of absorbing extrusion deformation, characterized in that: It is arranged at a position close to the end well, and comprises a first vertical reinforcement layer (2), a second vertical reinforcement layer (3) covering the first vertical reinforcement layer (2), and a jet-jet pile reinforcement layer (4) filled between the first vertical reinforcement layer (2), the second vertical reinforcement layer (3) and the end well side wall (5); The first vertical reinforcement layer (2) is made of solidified soil mixed with foam, and the second vertical reinforcement layer (3) is made of cement solidified soil. The first vertical reinforcement layer (2) covers the tunnel construction area and its edges extend outwards beyond the tunnel construction area. The axial distribution area of ​​the first vertical reinforcement layer (2) is within a range from 0.65 m from the end shaft side wall (5) to 10 to 15 m in the tunnel direction, and the circumferential distribution area of ​​the first vertical reinforcement layer (2) is within a range from the center of the tunnel construction area to 1 m outside the tunnel contour line (1); The axial distribution area of ​​the second vertical reinforcement layer (3) is from 0.65 m away from the end shaft side wall (5) to 10 to 15 m in the tunnel direction, and the circumferential distribution area of ​​the second vertical reinforcement layer (3) is from 1 m outside the tunnel contour line (1) to 3 to 5 m outside the tunnel contour line (1); The axial distribution area of ​​the jet grouting pile reinforcement layer (4) is within a range of 0.65 m from the end well side wall (5) to the tunnel direction, and the circumferential distribution area of ​​the jet grouting pile reinforcement layer (4) is within a range of 5 m from the center of the tunnel construction area to the tunnel contour line (1).

2. The shield end shaft reinforcement structure capable of absorbing extrusion deformation as claimed in claim 1 is characterized in that: The solidified soil mixed with foam used in the first vertical reinforcement layer (2) is prepared by mixing foam, a solidifying agent and in-situ soil. The foam is added in volume, and the proportion is 10% to 15% of the volume of the in-situ soil.

3. The shield end shaft reinforcement structure capable of absorbing extrusion deformation as claimed in claim 2 is characterized in that: The foam is made by mechanical foaming of anionic foaming agent, the foam diameter is 30-400 μm, the foam half-life is not less than 30 minutes, and the foam wet density is not more than 19 kg / m 3 .

4. The shield end shaft reinforcement structure capable of absorbing extrusion deformation as claimed in claim 2 is characterized in that: The curing agent is selected from any one of cement, inorganic soil curing agent and composite soil curing agent.

5. The shield end shaft reinforcement structure capable of absorbing extrusion deformation as claimed in claim 2 is characterized in that: The characteristics of the 28-day-old solidified soil mixed with foam are as follows: the unconfined compressive strength is not less than 1.2 MPa, the permeability coefficient is not greater than 1.0×10 -7 cm / s, wet density not more than 1300kg / m 3 .

6. The shield end shaft reinforcement structure capable of absorbing extrusion deformation as claimed in claim 1 is characterized in that: The cement-solidified soil used in the second vertical reinforcement layer (3) is prepared by mixing cement slurry and in-situ soil, and the water-cement ratio of the cement slurry is 0.8 to 1.

5.

7. The shield end shaft reinforcement structure capable of absorbing extrusion deformation as claimed in claim 6 is characterized in that: The characteristics of the cement-stabilized soil at 28 days are as follows: the unconfined compressive strength is not less than 1.0 MPa, the permeability coefficient is not greater than 1.0×10 -7 cm / s.

8. The shield end shaft reinforcement structure capable of absorbing extrusion deformation as claimed in claim 1 is characterized in that: The characteristics of the jet grouting pile reinforcement layer (4) at 28 days after hardening are as follows: the unconfined compressive strength is not less than 2.5 MPa, the permeability coefficient is not greater than 1.0×10 -7 cm / s.

9. A construction method for a shield end shaft reinforcement structure capable of absorbing extrusion deformation, comprising the shield end shaft reinforcement structure capable of absorbing extrusion deformation as claimed in any one of claims 1 to 8, characterized in that: The steps include: First, the end well side wall (5) is constructed, then the first vertical reinforcement layer (2) and the second vertical reinforcement layer (3) are constructed at the outer end of the end well side wall (5), and finally the rotary jet pile reinforcement layer (4) is constructed, and each area is constructed from bottom to top; When constructing the first vertical reinforcement layer (2) and the second vertical reinforcement layer (3), the lower part of the second vertical reinforcement layer (3) is constructed first, then the first vertical reinforcement layer (2) is constructed to the designed elevation, and finally the upper part of the second vertical reinforcement layer (3) is constructed.

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