Easily-disturbed soil layer staged excavation supporting structure system and construction method thereof

Abstract

The invention discloses an easily-disturbed soil layer staged excavation supporting structure system and a construction method thereof.The foundation pit is excavated in two stages, an easily-disturbed soil layer exists within the depth range below the first-stage excavation face, and the easily-disturbed soil layer staged excavation supporting structure system comprises a first-stage foundation pit support and a second-stage foundation pit support; the first-stage foundation pit support and the second-stage foundation pit support are connected into a whole through a rigidity coordinating piece, the first-stage foundation pit support comprises a first-stage support pile and a plurality of first-stage anchor rods tensioned on the first-stage support pile, and the second-stage foundation pit support comprises a second-stage steel pipe pile, a plurality of second-stage densely-arranged anchor rods tensioned on the second-stage steel pipe pile and a grouting reinforcing body. According to the method, disturbance of construction of the second-stage supporting piles and the anchor pulling structure to the built-in ends of the first-stage supporting piles is reduced to the maximum extent, foundation pit accidents are avoided, meanwhile, the problem of soil loss between the piles in the earth excavation period is solved, and the safety of stage excavation foundation pit engineering of soil layers prone to disturbance is guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of foundation pit support structures, and in particular to a staged excavation support structure system for easily disturbed soil layers and a construction method thereof. Background Art

[0002] With the development of modern cities, the number of foundation pits is increasing, and the scale and construction difficulty of foundation pits are constantly expanding. In the process of deep foundation pit construction, there are situations where the foundation pit is constructed in stages due to the difficulty of one-time excavation, design adjustments, insufficient construction funds, or the protection of ancient buildings.

[0003] If there are easily disturbed soil layers such as sand, silty soil, and high-water content clay below the first-phase excavation surface, if the second-phase support pile construction is carried out rashly, the embedded end of the first-phase support pile will be disturbed, causing the embedding failure and then the serious consequence of the first-phase support overturning. During the construction of the second-phase anchor structure and earth excavation, the easily disturbed soil will also be lost between the piles, reducing the safety of the foundation pit support system and posing accident hazards. Therefore, it is necessary to propose a staged excavation support structure system for easily disturbed soil layers and its construction method in order to address the disturbance risk during the construction of the second-phase support piles and anchor structure, as well as the problem of uncoordinated deformation of the two-phase support structure. Summary of the invention

[0004] The object of the present invention is to provide a staged excavation support structure system for easily disturbed soil layers and a construction method thereof, so as to solve the problems raised in the above-mentioned background technology.

[0005] To achieve the above-mentioned purpose, the present invention provides a staged excavation support structure system for easily disturbed soil layers, wherein the foundation pit is excavated in two stages, and there is an easily disturbed soil layer within the depth range below the first-stage excavation surface, and the staged excavation support structure system for easily disturbed soil layers comprises: a first-stage foundation pit support and a second-stage foundation pit support, wherein the first-stage foundation pit support and the second-stage foundation pit support are connected as a whole through a stiffness coordination member, wherein the first-stage foundation pit support comprises a first-stage support pile and a plurality of first-stage anchor rods tensioned on the first-stage support piles, and the second-stage foundation pit support comprises a second-stage steel pipe pile, a plurality of second-stage closely spaced anchor rods tensioned on the second-stage steel pipe piles, and a grouting reinforcement body.

[0006] In a preferred embodiment, multiple first-phase anchor rods and multiple second-phase close-spaced anchor rods are evenly spaced and inclined, the first-phase anchor rods are connected to the first-phase supporting piles through anchor head devices, the vertical spacing of the second-phase close-spaced anchor rods is 1.5-2m, and the horizontal spacing should be sufficient to avoid the first-phase supporting piles. One end of the first-phase anchor rods and the second-phase close-spaced anchor rods are fixedly connected to the first-phase supporting piles and the second-phase steel pipe piles respectively, and the other end of the second-phase close-spaced anchor rods extends to the easily disturbed soil layer.

[0007] In a preferred embodiment, the second-phase steel pipe piles are densely arranged with double rows of small-diameter steel pipes, the net distance between the second-phase steel pipe piles is less than 250mm, the pile tops are 7300mm higher than the first-phase excavation surface, and the safety distance between the second-phase steel pipe piles and the first-phase support piles is not less than times the diameter of the second-phase steel pipe piles.

[0008] In a preferred embodiment, a horizontal load transfer device is provided at the outer end of the second-phase close-spaced anchor rod. The horizontal load transfer device is made of concrete material, has a trapezoidal cross-section, and a vertical dimension of not less than the aperture of the second-phase close-spaced anchor rod + 100mm. The horizontal load transfer device is connected to the second-phase steel pipe piles through a fixing device and a compact body. The fixing device is anchored into the soil between the piles with steel bar nails, with a length of not less than 500mm, a vertical spacing of not more than 100mm, and a horizontal spacing of not more than times the spacing between the second-phase steel pipe piles. The compact body is filled between the horizontal load transfer device and the second-phase steel pipe piles.

[0009] In a preferred embodiment, the grouting reinforcement body is formed by grouting the grouting pipe between piles and the small advance conduit on the pile side, wherein the grouting pipe between piles is arranged in the second phase steel pipe pile along the vertical direction, and is used for grouting and solidifying the soil layer at the end of the first phase supporting pile, and the small advance conduits on the pile side are evenly spaced and inclined, and are used for grouting and reinforcing the soil between the piles. The depth range of the grouting reinforcement body is from the first phase excavation surface to 500 mm below the second phase excavation surface, and the plane range is from the outer edge of the second phase steel pipe pile to the outer edge of the first phase supporting pile.

[0010] In a preferred embodiment, the grouting pipes between piles adopt sleeve valve pipes, whose diameter is smaller than the diameter of the second-phase steel pipe piles, with a horizontal spacing of 400-800 mm, and the length of the sleeve valve pipes is consistent with the depth of the grouting reinforcement body.

[0011] In a preferred embodiment, the pile side advance small guide tube is a steel pipe, the front end of the pile side advance small guide tube is pointed boot-shaped, the inclination angle is - degree, the horizontal spacing is the same as the horizontal spacing of the second phase close-packed anchor rods, the vertical spacing is not more than 1m, and the length exceeds the plane range of the grouting reinforcement body by not less than 300mm.

[0012] In a preferred embodiment, the stiffness coordination part includes a concrete slab, a channel steel connector and a first anchor. The concrete slab is continuously arranged along the support edge line, the channel steel connector is arranged in a horizontal direction, the bottom surface of one end of the channel steel connector is welded to the top of the second-phase steel pipe pile, and the side surface of the other end of the channel steel connector is welded to the first anchor arranged in the first-phase support pile, so as to connect the double row of second-phase steel pipe piles and the first-phase support piles into a whole, and multiple groups of channel steel connectors and the first anchors are correspondingly arranged, and the multiple groups of channel steel connectors and the first anchors are arranged at equal intervals.

[0013] In a preferred embodiment, a reinforced support assembly is arranged between the embedded ends of the second-phase steel pipe piles and the first-phase supporting piles, and the horizontal spacing thereof is the same as the spacing between the first-phase supporting piles. The reinforced support assembly includes a hoop, a reinforced support, and a second anchor. The diameter of the arc-shaped end of the hoop is the wall thickness of the second-phase steel pipe pile + 10 mm, the height is not less than the diameter of the reinforced support + 50 mm, and the thickness is not less than 30 mm.

[0014] The present invention also provides a construction method for a staged excavation support structure system for easily disturbed soil layers, comprising the following steps: Step 1: Measure and lay out, and construct the first phase of support piles; Step 2: Excavate the foundation pit to the first-phase excavation surface, and construct the first-phase anchor bolts as the excavation progresses; Step 3: Lay out the grouting pipes between piles, grout to solidify the soil layer at the end of the first-stage supporting piles, and stop grouting when grouting appears around the top of the pipe; Step 4: Construction of double rows of second-phase steel pipe piles; Step 5: Construct the reinforced support assembly, roughen the corresponding range of the first-phase support pile to expose the steel bars, weld the second anchor to the exposed steel bars of the first-phase support pile, set the hoop at the corresponding position of the second-phase steel pipe pile, and weld the reinforced support to the second anchor and hoop; Step 6: Construct the rigidity coordination parts, roughen the corresponding range of the first-phase support piles to expose the steel bars, weld the first anchor to the exposed steel bars of the first-phase support piles, weld the channel steel connector to the second-phase steel pipe piles and the first anchor, and finally tie the steel bars and cast-in-place concrete to form the crown beam; Step 7: Excavate the foundation pit and construct the first second-phase dense anchor bolts and horizontal load transfer device; Step 8: Excavate to the position of the grouting of the small pipe in advance on the pile side, and carry out grouting of the small pipe in advance on the pile side to reinforce the soil between the piles. Stop grouting when grouting appears around the pipe top; Step 9: After the soil reinforcement is completed, construct the second phase of closely spaced anchor rods and horizontal load transfer devices at the corresponding positions; Step 10: Excavate to the second-phase excavation surface, and carry out grouting of the subsequent second-phase dense anchors and the small pipes in advance on the pile side as the excavation is carried out. Before the construction of each second-phase dense anchor, the soil between the piles is reinforced by grouting with small pipes in advance on the pile side. Stop grouting after grouting appears around the top of the pipe.

[0015] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention proposes a support structure system for staged excavation of easily disturbed soil layers and a construction method thereof, which minimizes the disturbance of the embedded ends of the first-phase support piles caused by the construction of the second-phase support piles and the anchor structure, avoids the occurrence of foundation pit accidents, and solves the problem of soil loss between piles during earth excavation, thereby ensuring the safety of staged excavation foundation pit projects in easily disturbed soil layers.

[0016] (2) The present invention strengthens the stiffness of double-row dense small-diameter steel pipe piles by closely spaced anchor rods, and connects the two-stage support system into a whole by a stiffness coordination member and a grouting reinforcement body, thereby avoiding problems such as cracking caused by the uncoordinated deformation of the two-stage support system.

[0017] (3) Compared with the traditional second-phase large-diameter bored pile solution, the present invention has higher safety and lower cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a main elevation cross-sectional view of the staged excavation support structure system for easily disturbed soil layers of the present invention; Figure 2 It is a side elevation view of the staged excavation support structure system of the easily disturbed soil layer of the present invention; Figure 3 It is a structural schematic diagram of the stiffness coordination member of the present invention; Figure 4 It is a structural schematic diagram of the horizontal load transfer device of the present invention; Figure 5 A top view of the reinforcing support assembly of the present invention; Figure 6 It is a schematic diagram of a hoop member of the present invention; Figure 7 It is a schematic diagram of the pile side advance small guide tube of the present invention; Fig. 8A It is a schematic diagram of construction steps one and two of the present invention; Figure 8B It is a schematic diagram of construction steps three and four of the present invention; Figure 8C It is a schematic diagram of construction steps five to seven of the present invention; Fig.8D It is a schematic diagram of construction step eight of the present invention; Fig. 8E It is a schematic diagram of construction steps nine and ten of the present invention.

[0019] Description of reference numerals: 1. Phase I support piles; 2. Phase I anchor rods; 3. Phase II steel pipe piles; 4. Phase II closely spaced anchor rods; 5. Grouting reinforcement bodies; 51. Grouting pipes between piles; 52. Small guide tubes ahead of pile sides; 521. Grouting holes; 6. Stiffness coordination parts; 61. Concrete slabs; 62. Channel steel connectors; 63. First anchors; 7. Phase I excavation surface; 8. Phase II excavation surface; 9. Easily disturbed soil layers; 10. Strengthened support components; 101. Hoops; 102. Strengthened support; 103. Second anchors; 11. Horizontal load transfer device. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present invention are described clearly and completely below. The embodiments of the present invention and all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention.

[0021] Embodiment 1: like Figures 1 to 8E As shown, the easily disturbed soil layer phased excavation support structure system of the preferred embodiment of the present invention, the foundation pit is excavated in two phases, and there is an easily disturbed soil layer 9 within the depth range below the first phase excavation surface 7, and the easily disturbed soil layer phased excavation support structure system includes: a first phase foundation pit support and a second phase foundation pit support, and the first phase foundation pit support and the second phase foundation pit support are connected into a whole through a stiffness coordination member 6. Among them, the first phase foundation pit support includes a first phase support pile 1 and a plurality of first phase anchor rods 2 tensioned on the first phase support pile 1, and the second phase foundation pit support includes a second phase steel pipe pile 3, a plurality of second phase closely spaced anchor rods 4 tensioned on the second phase steel pipe pile 3, and a grouting reinforcement body 5.

[0022] In this embodiment, a plurality of first-phase anchor rods 2 and a plurality of second-phase closely spaced anchor rods 4 are evenly spaced and tilted. The first-phase anchor rods 2 are connected to the first-phase support piles 1 through an anchor head device, and the anchor head device includes a double-jointed channel steel waist beam, an anchor pad, and an anchor structure. The second-phase closely spaced anchor rods are vertically closely spaced. Conventional anchor rod spacing is 3 to 4 m, while the second-phase closely spaced anchor rods 4 of the present invention are vertically closely spaced 1.5-2 m. The stability of the support system is ensured by encrypting the anchor rods, and the horizontal spacing should be sufficient to avoid the first-phase support piles 1. One end of the first-phase anchor rods 2 and the second-phase closely spaced anchor rods 4 are fixedly connected to the first-phase support piles 1 and the second-phase steel pipe piles 3, respectively, and the other end of the second-phase closely spaced anchor rods 4 extends to the easily disturbed soil layer 9.

[0023] Usually, deep foundation pit support piles are cast-in-place piles with large diameter and large spacing (such as 800@1500, 1000@1800 specifications). However, due to the easy loss of soil between piles in the easily disturbed strata, the large spacing of conventional piles will make it difficult to handle the piles. Therefore, small-spacing steel pipe piles are used, and the net distance between piles is less than 250mm, and the second-phase steel pipe piles 3 are densely arranged with double rows of small-diameter steel pipes. The dense arrangement of small-diameter steel pipes in this embodiment adopts: the diameter of the second-phase steel pipe piles is 159mm, the wall thickness is 6mm, and the spacing is 400mm. The pile top is 7300mm higher than the first-phase excavation surface, and the safety distance between the second-phase steel pipe piles 3 and the first-phase support piles 1 is not less than 4 times the diameter of the second-phase steel pipe piles.

[0024] The grouting reinforcement body 5 is formed by grouting the inter-pile grouting pipe 51 and the pile side advance small conduit 52, wherein the inter-pile grouting pipe 51 is arranged in the second-phase steel pipe pile 3 along the vertical direction, and is used for grouting and solidifying the soil layer at the end of the first-phase support pile 1. The pile side advance small conduit 52 is evenly spaced and inclined, and is used for grouting and reinforcing the soil between the piles. The depth range of the grouting reinforcement body 5 is from the first-phase excavation surface 7 to 500mm below the second-phase excavation surface 8, and the plane range is from the outer edge of the second-phase steel pipe pile 3 to the outer edge of the first-phase support pile 1. The inter-pile grouting pipe 51 adopts a sleeve valve pipe, whose diameter is smaller than the diameter of the second-phase steel pipe pile, and the horizontal spacing is 400~800mm. The length of the sleeve valve pipe is consistent with the depth of the grouting reinforcement body 5.

[0025] In order to prevent the loss of soil between piles and collapse of holes during the construction of the second-phase dense anchor rods 4, the pile side advance small conduit 52 is used to grout and reinforce the easily disturbed soil layer. The pile side advance small conduit 52 is a steel pipe, which is provided with a plurality of grouting holes 521. The front end of the pile side advance small conduit 52 is a pointed boot shape with an inclination angle of 15-20 degrees. The horizontal spacing is the same as the horizontal spacing of the second-phase dense anchor rods, the vertical spacing is not more than 1m, and the length exceeds the plane range of the grouting reinforcement body 5 by not less than 300mm to ensure the reinforcement effect of the grouting reinforcement body.

[0026] The stiffness coordination part 6 includes a concrete slab 61, a channel steel connector 62 and a first anchor 63. The concrete slab 61 is continuously arranged along the support edge line. The channel steel connector 62 is arranged in the horizontal direction. The bottom surface of one end of the channel steel connector 62 is welded to the top of the second-phase steel pipe pile 3, and the side surface of the other end of the channel steel connector 62 is welded to the first anchor 63 arranged in the first-phase support pile 1, so as to connect the double-row second-phase steel pipe piles 3 and the first-phase support pile 1 into a whole, and multiple groups of channel steel connectors 62 and the first anchor 63 are correspondingly arranged, and the multiple groups of channel steel connectors 62 and the first anchor 63 are arranged at equal intervals.

[0027] Embodiment 2: On the basis of Example 1, due to the large soil pressure in the lower part of the deep foundation pit, the corresponding second-phase close-spaced anchor rod 4 is subjected to a large axial tension. In order to ensure the anchoring effect, a horizontal load transfer device 11 is used between the second-phase steel pipe pile 3 and the second-phase close-spaced anchor rod 4. The outer end of the second-phase close-spaced anchor rod 4 is provided with a horizontal load transfer device 11, which is made of concrete material, has a trapezoidal cross-section, and a vertical dimension of not less than the aperture of the second-phase close-spaced anchor rod + 100mm. The horizontal load transfer device 11 is connected to the second-phase steel pipe pile 3 through a fixing device 111 and a compact body 112. The fixing device 111 is anchored into the soil between the piles with a steel bar nail, with a length of not less than 500mm, a vertical spacing of not more than 100mm, and a horizontal spacing of not more than 3 times the spacing of the second-phase steel pipe piles. The compact body 112 can be made of materials such as plain concrete and fluidized solidified soil, and is filled between the horizontal load transfer device 11 and the second-phase steel pipe pile 3.

[0028] In order to prevent the first-phase supporting pile 1 from being damaged by kicking, a reinforcing support assembly 10 is provided between the second-phase steel pipe pile 3 and the embedded end of the first-phase supporting pile 1, and its horizontal spacing is the same as the pile spacing of the first-phase supporting pile 1. The reinforcing support assembly 10 includes a hoop 101, a reinforcing support 102, and a second anchor 103. The diameter of the arc end of the hoop 101 is the wall thickness of the second-phase steel pipe pile + 10mm, the height is not less than the diameter of the reinforcing support 102 + 50mm, and the thickness is not less than 30mm.

[0029] Embodiment 3: The present invention also provides a construction method for a staged excavation support structure system for easily disturbed soil layers, comprising the following steps: Step 1: Measure and lay out, and construct the first phase support piles 1; Step 2: excavate the foundation pit to the first-stage excavation surface 7, and construct the first-stage anchor rod 2 as the excavation progresses; Step 3: Lay out the grouting pipe 51 between the piles, grout and solidify the soil layer at the end of the first-stage support pile 1, and stop grouting after grouting appears around the pipe top; Step 4: Construction of double rows of second-phase steel pipe piles 3; Step 5: construct the reinforced support assembly 10, roughen the corresponding area of ​​the first-phase support pile 1 to expose the steel bars, weld the second anchor 103 to the exposed steel bars of the first-phase support pile 1, set the hoop 101 at the corresponding position of the second-phase steel pipe pile 3, and weld the reinforced support 102 to the second anchor 103 and the hoop 101; Step 6: construct the stiffness coordination part 6, roughen the corresponding area of ​​the first-phase support pile 1 to expose the steel bars, weld the first anchor 63 to the exposed steel bars of the first-phase support pile 1, weld the channel steel connector 62 to the second-phase steel pipe pile 3 and the first anchor 63, and finally tie the steel bars and cast-in-place concrete to form a crown beam; Step 7: excavating the foundation pit, constructing the first second-stage closely spaced anchor rods 4 and the horizontal load transfer device 11; Step 8: excavate to the grouting position of the small advance pipe 52 on the pile side, grout the small advance pipe 52 on the pile side to reinforce the soil between the piles, and stop grouting after grouting appears around the pipe top; Step 9: After the soil reinforcement is completed, the second-stage densely spaced anchor rods 4 and the horizontal load transfer device 11 are constructed at the corresponding positions. If the soil layer has a high water content, the ends of the second-stage densely spaced anchor rods 4 can be protected by steel casings; Step 10: Excavate to the second-phase excavation surface 8, and grout the subsequent second-phase dense anchor rods 4 and the pile-side advanced small pipe 52 as the excavation is carried out. Before the construction of each second-phase dense anchor rod 4, the pile-side advanced small pipe 52 is first used for grouting to reinforce the soil between the piles, and the grouting is stopped after grouting appears around the pipe top.

[0030] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A support structure system for phased excavation of easily disturbed soil layers, wherein the foundation pit is excavated in two phases, and an easily disturbed soil layer (9) exists within a depth range below the first phase excavation surface (7), characterized in that: The staged excavation support structure system for easily disturbed soil layers comprises: a first-stage foundation pit support and a second-stage foundation pit support, wherein the first-stage foundation pit support and the second-stage foundation pit support are connected as a whole via a stiffness coordination member (6), wherein the first-stage foundation pit support comprises a first-stage support pile (1) and a plurality of first-stage anchor rods (2) tensioned on the first-stage support pile (1), and the second-stage foundation pit support comprises a second-stage steel pipe pile (3), a plurality of second-stage closely spaced anchor rods (4) tensioned on the second-stage steel pipe pile (3), and a grouting reinforcement body (5).

2. The staged excavation support structure system for easily disturbed soil layers according to claim 1 is characterized in that: The plurality of first-phase anchor rods (2) and the plurality of second-phase closely spaced anchor rods (4) are evenly spaced and inclined, the first-phase anchor rods (2) are connected to the first-phase support piles (1) via anchor head devices, the second-phase closely spaced anchor rods (4) have a vertical spacing of 1.5-2 m, and the horizontal spacing is sufficient to avoid the first-phase support piles (1), one end of the first-phase anchor rods (2) and the second-phase closely spaced anchor rods (4) are fixedly connected to the first-phase support piles (1) and the second-phase steel pipe piles (3), respectively, and the other end of the second-phase closely spaced anchor rods (4) extends to the easily disturbed soil layer (9).

3. The staged excavation support structure system for easily disturbed soil layers according to claim 2 is characterized in that: The second-phase steel pipe piles (3) are densely arranged double rows of small-diameter steel pipes, the net distance between the second-phase steel pipe piles (3) is less than 250 mm, the pile tops are 300 mm higher than the first-phase excavation surface (7), and the safety distance between the second-phase steel pipe piles (3) and the first-phase support piles (1) is not less than 4 times the diameter of the second-phase steel pipe piles.

4. The staged excavation support structure system for easily disturbed soil layers according to claim 3 is characterized in that: The outer end of the second-phase close-spaced anchor rod (4) is provided with a horizontal load transfer device (11). The horizontal load transfer device (11) is made of concrete material, has a trapezoidal cross-section, and a vertical dimension not less than the hole diameter of the second-phase close-spaced anchor rod + 100 mm. The horizontal load transfer device (11) is connected to the second-phase steel pipe pile (3) through a fixing device (111) and a compact body (112). The fixing device (111) is anchored into the soil between the piles by a steel bar nail, has a length not less than 500 mm, a vertical spacing not greater than 100 mm, and a horizontal spacing not greater than 3 times the spacing between the second-phase steel pipe piles. The compact body (112) is filled between the horizontal load transfer device (11) and the second-phase steel pipe pile (3).

5. The staged excavation support structure system for easily disturbed soil layers according to claim 4 is characterized in that: The grouting reinforcement body (5) is formed by grouting an inter-pile grouting pipe (51) and a pile-side advance small conduit (52), wherein the inter-pile grouting pipe (51) is arranged in the second-phase steel pipe pile (3) along the vertical direction, and is used for grouting and solidifying the soil layer at the pile end of the first-phase support pile (1); the pile-side advance small conduit (52) is evenly spaced and inclined, and is used for grouting and reinforcing the soil between the piles; the grouting reinforcement body (5) has a depth range from the first-phase excavation surface (7) to 500 mm below the second-phase excavation surface (8), and a plane range from the outer edge of the second-phase steel pipe pile (3) to the outer edge of the first-phase support pile (1).

6. The staged excavation support structure system for easily disturbed soil layers according to claim 5 is characterized in that: The inter-pile grouting pipe (51) is a sleeve valve pipe, the diameter of which is smaller than the diameter of the second-phase steel pipe pile, the horizontal spacing is 400-800 mm, and the length of the sleeve valve pipe is consistent with the depth of the grouting reinforcement body (5).

7. The staged excavation support structure system for easily disturbed soil layers according to claim 6 is characterized in that: The pile side leading small conduit (52) is a steel pipe, the front end of which is in the shape of a pointed boot, with an inclination angle of 15-20 degrees, a horizontal spacing being the same as the horizontal spacing of the second phase densely packed anchor rods, a vertical spacing being no greater than 1m, and a length exceeding the plane range of the grouting reinforcement body (5) by no less than 300mm.

8. The staged excavation support structure system for easily disturbed soil layers according to claim 1 is characterized in that: The rigidity coordination member (6) comprises a concrete slab (61), a channel steel connector (62) and a first anchor (63), wherein the concrete slab (61) is arranged continuously along the support edge line, the channel steel connector (62) is arranged in the horizontal direction, the bottom surface of one end of the channel steel connector (62) is welded to the top of the second-phase steel pipe pile (3), and the side surface of the other end of the channel steel connector (62) is welded to the first anchor (63) arranged in the first-phase support pile (1), so as to connect the double-row second-phase steel pipe pile (3) and the first-phase support pile (1) into a whole, and a plurality of groups of the channel steel connector (62) and the first anchor (63) are arranged correspondingly, and the plurality of groups of the channel steel connector (62) and the first anchor (63) are arranged at equal intervals.

9. The staged excavation support structure system for easily disturbed soil layers according to claim 1 is characterized in that: A reinforcing support assembly (10) is provided between the embedded ends of the second-phase steel pipe pile (3) and the first-phase support pile (1), and the horizontal spacing thereof is the same as the pile spacing of the first-phase support pile (1). The reinforcing support assembly (10) comprises a hoop (101), a reinforcing support (102), and a second anchor (103). The diameter of the arc-shaped end of the hoop (101) is the wall thickness of the second-phase steel pipe pile + 10 mm, the height is not less than the diameter of the reinforcing support (102) + 50 mm, and the thickness is not less than 30 mm.

10. A construction method for a staged excavation support structure system for easily disturbed soil layers, characterized in that: The steps include: Step 1: Survey and lay out, and construct the first phase of support piles (1); Step 2: excavate the foundation pit to the first-stage excavation surface (7), and construct the first-stage anchor rods (2) as the excavation progresses; Step 3: Laying out the grouting pipe (51) between the piles, grouting and solidifying the soil layer at the end of the first-stage supporting pile (1), and stopping the grouting after grouting appears around the pipe top; Step 4: Construction of double rows of second-phase steel pipe piles (3); Step 5: constructing the reinforced support assembly (10), roughening the corresponding area of ​​the first-phase support pile (1) to expose the steel bars, welding the second anchor (103) to the exposed steel bars of the first-phase support pile (1), setting the hoop (101) at the corresponding position of the second-phase steel pipe pile (3), and welding the reinforced support (102) to the second anchor (103) and the hoop (101); Step 6: construct the stiffness coordination piece (6), roughen the corresponding area of ​​the first-phase support pile (1) to expose the steel bars, weld the first anchor piece (63) to the exposed steel bars of the first-phase support pile (1), weld the channel steel connector (62) to the second-phase steel pipe pile (3) and the first anchor piece (63), and finally tie the steel bars and cast in-situ concrete to form a crown beam; Step 7: excavating the foundation pit, constructing the first second-stage closely spaced anchor rods (4) and the horizontal load transfer device (11); Step 8: excavate to the grouting position of the small pipe (52) on the side of the pile, grout the small pipe (52) on the side of the pile to reinforce the soil between the piles, and stop grouting when grouting appears around the pipe top; Step 9: After the soil layer is reinforced, the second-stage closely spaced anchor rods (4) and the horizontal load transfer device (11) are constructed at the corresponding positions; Step 10: excavate to the second-stage excavation surface (8), and perform grouting of the subsequent second-stage closely spaced anchor rods (4) and the small pipes (52) ahead of the pile side as the excavation progresses. Before the construction of each second-stage closely spaced anchor rod (4), the small pipes (52) ahead of the pile side are first used for grouting to reinforce the soil between the piles. The grouting is stopped after grouting appears around the pipe top.

Images