Deep foundation pit support and support construction process

Abstract

Supporting piles or pipe piles are arranged outside an underground foundation of a building in a surrounding mode, row piles are arranged on the peripheries of the supporting piles or the pipe piles, crown beams are arranged on the supporting piles or the pipe piles, anchor cables are arranged on the crown beams, and the anchor cables obliquely downwards sequentially penetrate through the supporting piles or the pipe piles, then penetrate through the row piles and extend into an external soil layer; net hanging sprayed concrete is arranged on one side, close to the building underground foundation, of the inner side of each pipe pile or support pile; a soil layer on the edge of the top of the deep foundation pit slopes downwards towards the underground foundation of the building, and net hanging sprayed concrete is arranged on the slope surface. Row piles are arranged to prevent water seepage into the deep foundation pit due to too high water pressure outside the deep foundation pit, then pipe piles or support piles are arranged, and hanging net spraying concrete is arranged outside the pipe piles or the row piles to prevent water from seeping into the deep foundation pit from the positions between the piles; the tubular piles or the supporting piles are fixed in a soil layer outside the deep foundation pit through the anchor cables, the adjacent tubular piles or the adjacent supporting piles are connected into a whole through the crown beams, net hanging and concrete spraying are conducted on the inner sides of the piles after each layer of earth is excavated, and the deep foundation pit always keeps good structural strength.

Description

Technical Field

[0001] The present invention relates to the technical field of engineering construction, and in particular to a deep foundation pit support and a support construction process. Background Art

[0002] Most of the existing supports in deep foundation pits are temporary, which makes it difficult to ensure stability after subsequent deep foundation pit excavation. The slopes of deep foundation pits are subject to the risk of landslide and water seepage, and the construction process is complicated and cannot be carried out in an orderly and process-based manner. Summary of the Invention

[0003] The purpose of the present invention is to provide a deep foundation pit support and support construction process to solve the above problems existing in the prior art.

[0004] The technical solution of the present invention to solve the above technical problems is as follows:

[0005] A deep foundation pit support comprises a mesh sprayed concrete, a row of piles, a pipe pile, a supporting pile, an anchor cable and a crown beam. The supporting piles or pipe piles are arranged outside the underground foundation of a building. Rows of piles are arranged on the periphery of some supporting piles or pipe piles. Crown beams are arranged on some supporting piles or pipe piles. Anchor cables are arranged on some crown beams. The anchor cables are inclined downward and successively penetrate the supporting piles or pipe piles and then penetrate the row of piles to extend into the external soil layer. A mesh sprayed concrete is arranged on the inner side of the pipe piles or supporting piles close to the underground foundation of the building. The soil layer at the top edge of the deep foundation pit slopes downward toward the underground foundation of the building, and a mesh sprayed concrete is arranged on the slope.

[0006] On the basis of the above technical solution, the present invention can also be improved as follows.

[0007] Furthermore, some pipe piles or support piles are arranged in two rows in parallel, and inter-pile reinforcement is provided between the two rows of pipe piles or between the two rows of support piles.

[0008] A further beneficial effect of adopting the above method is to improve the structural strength and connection stability of the pipe piles or support piles.

[0009] Furthermore, the crown beam includes a first crown beam and a second crown beam. The first crown beam is set on the top of the pipe pile, and the second crown beam is set on the top of the supporting pile. Steel sections are planted in the supporting pile, and the top of the steel sections passes through the second crown beam.

[0010] A further beneficial effect of the above is that the embedded steel can improve the structural strength of the supporting piles.

[0011] Furthermore, a diversion ditch is provided at the outer edge of the top of the deep foundation pit, and a drainage ditch is provided at the bottom of the deep foundation pit outside the underground foundation of the building.

[0012] The above method has the following further beneficial effects: the intercepting ditch can prevent water from flowing into the deep foundation pit; the drainage ditch can collect the water in the foundation pit, which is convenient for subsequent discharge.

[0013] Another technical solution of the present invention is as follows:

[0014] A deep foundation pit support construction process comprises the following steps:

[0015] Step 01: Design a deep foundation pit support scheme: Select different support methods based on the properties of the soil layer, groundwater conditions, and the surrounding environment of the deep foundation pit;

[0016] Step 02: Site leveling: Level the ground in the construction area;

[0017] Step 03: Engineering pile construction: row pile construction, pipe pile construction and support pile construction;

[0018] Step 04, deep foundation pit excavation construction: adopt layered construction, first carry out the first layer of earthwork excavation, crown beam construction, anchor cable construction and mesh spraying concrete construction; then carry out the next layer of earthwork excavation and the next layer of mesh spraying concrete construction.

[0019] Furthermore, the method further comprises the following steps:

[0020] Step 05. Construction of intercepting ditches and drainage ditches: Open an intercepting ditch at the outer edge of the top of the deep foundation pit, and open a drainage ditch outside the underground foundation of the building at the bottom of the deep foundation pit.

[0021] The beneficial effects of the present invention are as follows: rows of piles are set to prevent water from seeping into the deep foundation pit due to excessive water pressure outside the deep foundation pit, and then pipe piles or support piles are set, and mesh spraying is set outside the pipe piles or rows of piles to further prevent water from seeping into the deep foundation pit from between the piles; anchor cables fix the pipe piles or support piles in the soil layer outside the deep foundation pit, and crown beams connect adjacent pipe piles or adjacent support piles into a whole. At the same time, after each layer of earthwork is excavated, mesh spraying is carried out on the inside of the pipe piles or support piles to ensure that the deep foundation pit always maintains good structural strength after excavation, thereby improving the stability of the deep foundation pit after excavation. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a flowchart of a deep foundation pit support construction process according to the present invention;

[0023] Figure 2 This is a structural schematic diagram of a deep foundation pit support according to the present invention;

[0024] Figure 3-19 A diagram showing a specific embodiment of the present invention;

[0025] Figure 20 This is a schematic diagram of the first crown beam structure of a deep foundation pit support according to the present invention;

[0026] Figure 21 This is a schematic diagram of the second crown beam structure of a deep foundation pit support according to the present invention;

[0027] Figure 22This is a schematic diagram of pipe piles and mesh spraying for deep foundation pit support according to the present invention;

[0028] Figure 23 This is a schematic diagram of support piles and mesh spraying for deep foundation pit support according to the present invention;

[0029] Figure 24 This is a schematic structural diagram of an anchor cable portion of a deep foundation pit support according to the present invention;

[0030] Figure 25 This is a schematic diagram of a pipe pile and inter-pile reinforcement structure for deep foundation pit support according to the present invention;

[0031] Figure 26 This is a schematic diagram of the supporting piles and inter-pile reinforcement structure for deep foundation pit support according to the present invention.

[0032] In the accompanying drawings, the components represented by the reference numerals are as follows:

[0033] 1. Hanging mesh spraying concrete; 1-1. Steel plate mesh; 1-2. Transverse tie steel bars; 1-3. Drain holes; 1-4. Reinforced soil nails; 1-5. Spraying concrete; 2. Piles; 3. Pipe piles; 4. Support piles; 4-1. Steel sections; 5. Reinforcement between piles; 6. Building underground pile foundation; 7. Anchor cable; 7-1. Anchor pad; 7-2. Anchor; 7-3. Steel strand; 8. Crown beam; 8-1. First crown beam; 8-2. Second crown beam; 9. Building underground foundation; 10. Intercepting ditch; 11. Drainage ditch. DETAILED DESCRIPTION

[0034] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0035] Example 1

[0036] like Figure 2-26 As shown, a deep foundation pit support includes a hanging mesh sprayed concrete 1, a row of piles 2, a pipe pile 3, a supporting pile 4, an anchor cable 7 and a crown beam 8. The supporting piles 4 or the pipe piles 3 are arranged outside the underground foundation 9 of the building. Some of the supporting piles 4 or the pipe piles 3 are provided with a row of piles 2 on the periphery, some of the supporting piles 4 or the pipe piles 3 are provided with a crown beam 8, and some of the crown beams 8 are provided with anchor cables 7. The anchor cables 7 are inclined downward and pass through the supporting piles 4 or the pipe piles 3 in turn and then pass through the row of piles 2, extending into the external soil layer; the inner side of the pipe piles 3 or the supporting piles 4 close to the underground foundation 9 of the building is provided with a hanging mesh sprayed concrete 1; the soil layer at the top edge of the deep foundation pit slopes downward toward the underground foundation 9 of the building, and a hanging mesh sprayed concrete 1 is provided on the slope.

[0037] Example 2

[0038] like Figure 25 、 26 As shown, this embodiment is a further improvement on the basis of embodiment 1, specifically as follows:

[0039] Some pipe piles 3 or support piles 4 are arranged in two rows, and between the two rows of pipe piles 3 or the two rows of support piles 4, there are inter-pile reinforcements 5. Cement-soil mixing piles improve the structural strength and connection stability of pipe piles 3 or support piles 4.

[0040] Example 3

[0041] like Figure 20 、 21 As shown, this embodiment is a further improvement on the basis of embodiment 2, specifically as follows:

[0042] The crown beam 8 includes a first crown beam 8-1 and a second crown beam 8-2. The first crown beam 8-1 is placed on top of the tubular pile 3, and the second crown beam 8-2 is placed on top of the support pile 4. The support pile 4 is embedded with a steel section 4-1, and the top of the steel section 4-1 passes through the second crown beam 8-2. The embedded steel section 4-1 can improve the structural strength of the support pile 4.

[0043] Example 4

[0044] like Figure 24 As shown, this embodiment is a further improvement on the basis of embodiment 3, specifically as follows:

[0045] The head end of the steel strand 7 - 3 in the anchor cable 7 extending outside the crown beam 8 is fixed by an anchor 7 - 2 arranged on the side wall of the crown beam 8 , and an anchor plate 7 - 1 is arranged between the anchor 7 - 2 and the crown beam 8 .

[0046] The mesh sprayed concrete 1 includes a steel plate mesh 1-1, transverse tie steel bars 1-2, reinforced soil nails 1-4 and sprayed concrete 1-5. The steel plate mesh 1-1 is fixedly arranged on the outside of the pipe pile 3 or the support pile 4, and the transverse tie steel bars 1-2 are fixedly arranged on the outside of the steel plate mesh 1-1. Reinforced soil nails 1-4 are nailed between adjacent pipe piles 3 or support piles 4, and sprayed concrete 1-5 is sprayed outside the transverse tie steel bars 1-2; a number of drainage holes 1-3 are opened on the mesh sprayed concrete 1 outside the pipe pile 3.

[0047] Example 5

[0048] like Figure 3-19 As shown, this embodiment is a further improvement on the basis of embodiment 4, specifically as follows:

[0049] A cut-off ditch 10 is provided at the outer edge of the top of the deep foundation pit, and a drainage ditch 11 is provided at the bottom of the deep foundation pit outside the building underground foundation 9. The cut-off ditch 10 can prevent water from flowing into the deep foundation pit; the drainage ditch 11 can collect the water in the deep foundation pit for subsequent discharge.

[0050] Example 6

[0051] like Figure 1 As shown, this embodiment is a construction process for any deep foundation pit support of construction embodiments 1 to 5, including the following steps:

[0052] Step 01: Design a deep foundation pit support scheme: Select different support methods based on the properties of the soil layer, groundwater conditions, and the surrounding environment of the deep foundation pit;

[0053] Step 02: Site leveling: Level the ground in the construction area;

[0054] Step 03, engineering pile construction: construction of pile row 2, pipe pile 3 and support pile 4;

[0055] Step 04, deep foundation pit excavation construction: adopt layered construction, first carry out the first layer of earthwork excavation, construction of crown beam 8, construction of anchor cable 7 and construction of mesh spraying concrete 1; then carry out the next layer of earthwork excavation, and construction of the next layer of mesh spraying concrete 1.

[0056] During the specific implementation, earth excavation should be avoided as far as possible during the rainy season. After excavation, the underground foundation of the building 9 should be constructed as soon as possible and backfilled in time to reduce the exposure time of the foundation pit. Mechanical excavation is used for general excavation of the foundation pit, and manual excavation is used with at least 30cm reserved near the bottom of the pit. The following requirements should be met: no collision with measurement marks, no collision or dragging of engineering piles, and no impact on the underground pile foundation of the building 6; mechanical excavation should avoid adverse effects on the engineering piles and the anchor ends of the anchor cables 7, and excavation machinery shall not walk directly on the top of the engineering piles; the temporary slope formed during the earth excavation process shall not be steeper than 1:1.5 to ensure the safety of construction operations. The excavated earth should be transported out of the construction site in a timely manner and shall not be piled on the top of the deep foundation pit.

[0057] Example 7

[0058] like Figure 1 As shown, this embodiment is a further improvement on the basis of Example 6, specifically as follows:

[0059] The method further includes the following steps: Step 05, construction of intercepting ditch 10 and drainage ditch 11: constructing intercepting ditch 10 at the outer edge of the top of deep foundation pit, and constructing drainage ditch 11 outside the underground foundation 9 of the building at the bottom of deep foundation pit.

[0060] Example 8

[0061] like Figure 3-19 As shown, this embodiment is a further improvement on the basis of embodiment 7, specifically as follows:

[0062] The construction of pipe pile 3 specifically includes: driving a single pipe pile into the soil layer according to the designed pile position;

[0063] During implementation, Pipe Pile 3 should not be connected. Its quality should comply with the technical requirements of the "Technical Standard for Prestressed Concrete Pipes" JGJ / 406-2017, the National Building Standard Design Drawings 10G409 "Prestressed Concrete Pipe Pile 3," and relevant regulations and specifications. The allowable deviation in pile position is no more than ±5.0cm, and the verticality deviation is 0.5 / 100. During delivery, the top elevation should be strictly controlled, with a top elevation deviation of no more than 50mm. Before construction, the appearance and quality of Pipe Pile 3 should be inspected, the position should be verified, and the driving sequence should be arranged appropriately. Hammering should be done with heavy hammers and light strikes, and the sinking process should be continuous. Pile verticality should be checked during construction; after construction, the pile integrity should be tested using the low-strain method. No fewer than 20% of the total number of piles should be tested, and no fewer than 10 piles should be inspected.

[0064] The construction of the support pile 4 specifically includes: using a rotary drilling rig or a long spiral drilling rig to pre-drill a hole and then backfilling with plain soil, using a powerful mixing pile driver to mix the soil in the hole to form a cement support pile 4, and finally using a plug-in machine to insert the steel 4-1;

[0065] During construction, support pile 4 was constructed using a Φ650 high-powered uniaxial cement-soil mixing machine. P.042.5 cement was used, with a cement content of 25%, a water-cement ratio of 1.5-2.0, and a void content of 7%. The unconfined compressive strength of support pile 4 at 28 days of age was to be no less than 0.5 MPa. Subsequent deep foundation pit excavation was not permitted until the cement-soil mixture reached the design strength and was at least 28 days old.

[0066] The position of support pile 4 is allowed to deviate by +20mm, and the verticality requirement for section steel 4-1 is no greater than 1 / 200. Section steel 4-1 should be inserted within 30 minutes after the completion of support pile 4 construction. Before insertion, its flatness and joint weld quality should be inspected. Section steel 4-1 should be derusted while dry and then coated with a friction reducer. Section steel 4-1 and crown beam 8 should be separated by a non-compressible material (felt) to facilitate removal and recovery.

[0067] The construction of the anchor cable 7 specifically includes: using a jet grouting drill to penetrate the silt layer at a construction angle of 30 degrees downward.

[0068] In specific implementation, P.O42.5 cement is used, the length of the rotary jet section is not less than 3.0m and must pass through the silt layer, the rotary jet pressure is 20Mpa, the water-cement ratio is 1.0, and the cement content is 25%.

[0069] The construction of mesh spraying concrete 1 specifically includes: when carrying out the slope surface mesh spraying concrete 1 construction: after mechanical excavation, the slope surface is repaired manually, short steel bars are vertically driven into the slope surface as a thickness mark, and spraying is carried out from bottom to top, with the jet vertically spraying the surface; when carrying out the inter-pile mesh spraying concrete 1 construction: steel plate mesh 1-1 and horizontal tie steel bars 1-2 are welded on the outside of the pipe piles 3 or support piles 4, and steel soil nails 1-4 are nailed between adjacent pipe piles 3 or support piles 4, and then the spraying operation is carried out.

[0070] During the specific implementation, one layer should be excavated and sprayed to protect it. It is strictly prohibited to excavate too deep or too long. Moisturizing maintenance should be carried out after the spraying operation is completed.

[0071] Example 9

[0072] like Figure 3-19 As shown, this embodiment is a further improvement on the basis of embodiment 8, specifically as follows:

[0073] Deep foundation pit monitoring is carried out throughout the construction process. Specifically, the monitoring includes horizontal and vertical displacements of pile tops, deep-layer horizontal displacements, horizontal and vertical displacements of slope tops, axial tension of anchor cables, support axial forces, and building and road settlements.

[0074] The beneficial effects of the present invention are as follows: rows of piles 2 are set to prevent water from seeping into the deep foundation pit due to excessive water pressure outside the deep foundation pit, and then pipe piles 3 or support piles 4 are set, and mesh spraying 1 is set outside the pipe piles 3 or rows of piles 4 to further prevent water from seeping into the deep foundation pit from between the piles; anchor cables 7 fix the pipe piles 3 or support piles 4 in the soil layer outside the deep foundation pit, and crown beams 8 connect adjacent pipe piles 3 or adjacent support piles 4 into a whole. At the same time, after each layer of earthwork is excavated, mesh spraying 1 is carried out on the inner side of the pipe piles 3 or support piles 4 to ensure that the deep foundation pit always maintains good structural strength after excavation, thereby improving the stability of the deep foundation pit after excavation. Specific embodiments

[0076] A geotechnical engineering survey was conducted in the construction area. According to the Geotechnical Engineering Survey Report, the soil conditions within the scope of deep foundation pit excavation are as follows:

[0077] 1 Plain fill: Age and cause Qm ml Distributed throughout the site, the top layer is buried at a depth of 0.4m-4.4m. It is a variegated, loose layer composed of clay, angular gravel, and crushed stone. The top layer contains plant roots, and the composition is chaotic and uneven. This is a recent landfill, less than 5 years old.

[0078] 2.1 Silty clay: age and origin Q4 al+pl , locally distributed, the top of the layer is buried at a depth of 0.4m-3.2m, the thickness is 0.6m-2.9m, gray-brown, yellow-brown, plastic, saturated, and contains a small amount of iron and manganese oxides.

[0079] 2.2 Silt: Origin: Q4, local distribution, top burial depth 1.0m-3.4m, thickness 1.0m-4.8m, gray-brown, plastic, contains a small amount of organic matter, occasional spiral core.

[0080] 2.3 Silty clay: age and origin Q4 al+pl, locally distributed, the top of the layer is buried at a depth of 0.8m-7.4m, the thickness is 0.6m-3.0m, gray-brown, yellow-brown, soft-plastic, saturated, and contains a small amount of iron and manganese oxides.

[0081] 2.4 Silty clay: Age and origin al , locally distributed, the top of the layer is buried at a depth of 4.6m-7.0m, the thickness is 0.6m-3.4m, gray-brown, plastic, contains a small amount of organic matter, and occasionally spiral cores.

[0082] 2.5 Silty clay: Age and origin Q4 al+pl , locally distributed, the top of the layer is buried at a depth of 6.0-8.0m, the thickness is 0.6-1.8m, gray-brown, yellow-brown, plastic, saturated, and contains a small amount of iron and manganese oxides.

[0083] 3.1 Silty clay: Age and origin Q3 al+pl , locally distributed, the top of the layer is buried at a depth of 1.0m-9.6m, the thickness is 0.8m-5.2m, yellowish brown, hard-plastic, saturated, and contains a small amount of iron and manganese oxides.

[0084] 3.2 Silty clay: Age and origin Q3 al+pl , distributed throughout the field, with the top of the layer buried at a depth of 2.0m-12.6m, a thickness of 3.6m-17.8m, brownish yellow, hard plastic, containing a small amount of iron-manganese oxides, iron-manganese nodules, and lumpy kaolin.

[0085] 3a Silty Clay: Age and Origin Q3 al+pl , locally distributed, the top of the layer is buried at a depth of 8.0m-15.2m, the thickness is 0.6m-3.4m, brownish yellow, hard-plastic, containing a small amount of iron-manganese oxides, iron-manganese nodules, and lumpy kaolin.

[0086] 3.3 Silty clay with gravel: Age and origin Q3 al+pl , locally distributed, the top of the layer is buried at a depth of 10.0m-20.4m, with a thickness of 0.1m-5.8m, reddish brown, hard plastic, brownish yellow, hard plastic, containing a small amount of iron-manganese oxides, iron-manganese nodules, and lumpy kaolin, with a small amount of breccia and gravel in some areas.

[0087] 4.1 Strongly weathered sandstone: Age and origin K, partially exposed, layer top buried at a depth of 10.8m-24.0m, thickness of 0.5m-4.7m, blue-gray, brown-yellow, gray-white and other colors, most of its minerals have been weathered into sandy state, the original rock structure and texture have been destroyed, the core is mostly slag-like and debris-like, and moderately weathered mud sandstone fragments are seen in some parts.

[0088] 4.2 Moderately Weathered Sandstone: Age and Origin: K, partially exposed, with a top buried depth of 11.4m-28.7m and a maximum exposed thickness of 11.6m. Colors include bluish-gray, brownish-yellow, and grayish-white, with a sandy texture and layered structure, primarily composed of quartz, silica, feldspar particles, and clay minerals. Drilled cores are relatively complete, mostly columnar, and the rock mass is relatively intact. Based on statistical data from compressive strength tests, this rock formation is classified as extremely soft, with a basic rock mass quality grade of V. Partially, it is sandy mudstone.

[0089] Groundwater conditions

[0090] The groundwater in this construction area is the upper stagnant water and bedrock fissure water stored in the fill.

[0091] Upper stagnant water: Found in plain fill, it is primarily replenished by atmospheric precipitation and surface water infiltration, and drained by vertical runoff and evaporation. Surveys revealed that the upper stagnant water level ranged from 0.20m to 1.60m deep and from 15.26m to 17.28m above sea level. The upper stagnant water lacks a uniform free surface.

[0092] Bedrock fissure water: exists in the bedrock and has no impact on this foundation pit project.

[0093] Sectional construction

[0094] Divide the deep foundation pit into AB, BC, CD, DE, EF, FG, GH, HJ, JK, KK1, K1K2, K2L, LM, MN, NO, OP, and PA sections.

[0095] Determine the support method for each section

[0096] AB section: The soil layers from top to bottom are 1 plain fill, 2.1 silty clay and 3.2 silty clay. The support method of AB section is determined to be downward sloping + slope surface mesh spraying concrete 1.

[0097] Section BC: The soil layers from top to bottom are 1 plain fill, 2.2 silt and 3.2 silty clay. The support method for section AB is determined to be downward slope + 1 mesh sprayed concrete on the slope + 2 rows of piles + 3 pipe piles + 8 crown beams + 1 mesh sprayed concrete inside pipe pile 3; 2 rows of piles are used. Cement soil mixing pile, L = 5.0m@0.35m; pipe pile 3 is PRC I500(100)AB type pipe pile L = 12.0m@0.8m.

[0098] CD section: The soil layers from top to bottom are 1 plain fill, 2.2 silt and 3.2 silty clay. The support method of CD section is determined to be downward slope + 1 mesh sprayed concrete on the slope surface + 2 rows of piles + 4 supporting piles + 8 crown beams + 1 mesh sprayed concrete on the inner side of supporting pile 4; the pile row 2 is 2 rows Cement soil mixing pile, L = 6.0m@0.35m; support pile 4 is a pre-guided hole Uniaxial cement-soil mixing pile, L=11.3m@0.9m, inserted H500 steel L=12.0m.

[0099] Section DE: The soil layers from top to bottom are 1 plain fill, 2.1 silty clay, 2.2 silt, 2.3 silty clay and 3.2 silty clay. The support method for Section DE is determined to be downward slope + 1 mesh sprayed concrete on the slope + 2 rows of piles + 4 supporting piles + 8 crown beams + 1 mesh sprayed concrete on the inside of supporting pile 4; row 2 of piles is 2 rows Cement soil mixing pile, L = 6.0m@0.35m; support pile 4 is a pre-guided hole Uniaxial cement-soil mixing pile, L=11.3m@0.9m, inserted H500 steel L=12.0m.

[0100] Section EF: The soil layers from top to bottom are 1 plain fill, 2.1 silty clay, 2.2 silt, 2.3 silty clay, 3.1 silty clay, and 3.2 silty clay. The support method for section EF is determined to be downward slope + slope mesh spraying 1 + double-row pipe piles 3 + pile reinforcement 5 + crown beam 8 + pipe pile 3 inner side mesh spraying 1; the front row of pipe piles 2 are PRC I500 (100) AB type pipe piles with a L of 12.0m@0.8m, and the back row of piles are PRC I500 (100) AB type pipe piles with a L of 12.0m@1.2m; the pile reinforcement is multiple Cement soil mixing pile L=5.5m@0.35m.

[0101] FG section: The soil layers from top to bottom are 1 plain fill, 2.2 silt, 2.3 silty clay, 3.1 silty clay, 3.2 silty clay. The FG section is determined to be supported by downward sloping + 1 mesh spraying concrete on the slope surface + 4 double rows of supporting piles + 5 reinforcement between piles + 8 crown beams + 1 mesh spraying concrete on the inner side of supporting pile 4; the front row of supporting piles 4 are pre-guided holes. Uniaxial cement soil mixing pile, L = 11.3m @ 0.9m, inserted H500 steel L = 12.0m, rear piles are pre-guided holes Uniaxial cement-soil mixing pile, L = 11.3m @ 0.9m, inserted H500 steel L = 12.0m; multiple reinforcements between piles Cement soil mixing pile L=8.0m@0.35m.

[0102] GH section: The soil layers from top to bottom are 1 plain fill, 2.2 silt, 2.3 silty clay, 3.1 silty clay, 3.2 silty clay. The support method for GH section is determined to be downward slope + slope surface mesh spraying 1 + pile row 2 + pipe pile 3 + crown beam 8 + pipe pile 3 inner mesh spraying 1; pile row 2 is 2 rows Cement soil mixing pile, L = 6.0m@0.35m; pipe pile 3 is PRC I500(100)AB type pipe pile L = 12.0m@0.8m.

[0103] HJ section: The soil layers from top to bottom are 1 plain fill, 2.1 silty clay, 3.1 silty clay and 3.2 silty clay. The support method of HJ section is determined to be downward sloping + slope surface mesh spraying concrete 1.

[0104] JK section: The soil layers from top to bottom are 1 plain fill and 3.2 silty clay. The support method for JK section is determined to be downward slope + 2 rows of piles + 3 pipe piles + 8 crown beams + 1 mesh sprayed concrete on the inner side of the pipe piles; 2 rows of piles are 2 rows. Cement soil mixing pile, L = 5.0m@0.35m; pipe pile 3 is PRC I500(100)AB type pipe pile L = 12.0m@0.8m.

[0105] KK1 section: The soil layers from top to bottom are 1 plain fill, 2.2 silt, 2.3 silty clay and 3.2 silty clay. The support method for KK1 section is determined to be downward slope + 2 rows of piles + 3 pipe piles + 8 crown beams + 1 mesh sprayed concrete on the inner side of the pipe piles; 2 rows of piles are 2 rows Cement soil mixing pile, L = 5.5m@0.35m; pipe pile 3 is PRC I500(100)AB type pipe pile L = 12.0m@0.8m.

[0106] Section K1K2: The soil layers are 1 plain fill, 2.2 silt, 2.3 silty clay, 2.4 silty clay, 3.1 silty clay and 3.2 silty clay from top to bottom. The support method for Section K1K2 is determined to be downward slope + 1 mesh spraying concrete on the slope surface + 3 double rows of pipe piles + 5 reinforcement between piles + 8 crown beams + 1 mesh spraying concrete on the inner side of pipe pile 3; the front row of pipe piles 3 are PRC I500(100)AB type pipe piles with a L of 12.0m@0.8m, and the back row of piles are PRC I500(100)AB type pipe piles with a L of 12.0m@1.2m; the reinforcement between piles is multiple Cement soil mixing pile L=7.5m@0.35m.

[0107] K2L section: The soil layers from top to bottom are 1 plain fill, 2.2 silt, 2.3 silty clay, 2.4 silty clay, 2.5 silty clay and 3.2 silty clay. The support method for K2L section is determined to be downward sloping + 1 mesh sprayed concrete on the slope surface + 2 rows of piles + 4 supporting piles + 8 crown beams + 7 anchor cables + 1 mesh sprayed concrete on the inner side of the 4 supporting piles; the pile row 2 is 2 rows Cement soil mixing pile, L = 6.0m@0.35m; support pile 4 is a pre-guided hole Uniaxial cement soil mixing pile, L = 11.3m @ 0.9m, inserted H500 steel L = 12.0m; anchor cable 7 is High-pressure jet grouting anchor L=20.0m@1.35m, design value of tension N=160kN, length of jet spraying section 5.0m.

[0108] LM section: The soil layers from top to bottom are 1 plain fill, 2.2 silt, 2.3 silty clay, 2.4 silty clay, 3.1 silty clay and 3.2 silty clay. The support method of LM section is determined to be downward slope + 1 mesh spraying concrete on the slope surface + 2 rows of piles + 4 supporting piles + 8 crown beams + 7 anchor cables + 1 mesh spraying concrete on the inner side of the supporting pile 4; the pile row 2 is 2 rows Cement soil mixing pile, L = 6.0m@0.35m; support pile 4 is a pre-guided hole Uniaxial cement soil mixing pile, L = 11.3m @ 0.9m, inserted H500 steel L = 12.0m; anchor cable 7 is High-pressure jet grouting anchor L=21.0m@0.9m Tensile design value N=160kN Jet spraying section length 5.0m.

[0109] MN section: The soil layers from top to bottom are 1 plain fill, 2.2 silt, 2.3 silty clay, 2.4 silty clay, 3.1 silty clay and 3.2 silty clay. The support method for MN section is determined to be downward slope + 1 mesh sprayed concrete on the slope surface + 2 rows of piles + 4 supporting piles + 8 crown beams + 7 anchor cables + 1 mesh sprayed concrete on the inside of 4 supporting piles; 2 rows of piles are 2 rows. Cement soil mixing pile, L = 6.0m@0.35m; support pile 4 is a pre-guided hole Uniaxial cement soil mixing pile, L = 11.3m @ 0.9m, inserted H500 steel L = 12.0m; anchor cable 7 is High-pressure jet grouting anchor L=21.0m@1.8m Tensile design value N=160kN Jet spraying section length 5.0m.

[0110] Section NO: The soil layers from top to bottom are 1 plain fill, 2.2 silt, 2.3 silty clay, 2.4 silty clay, 3.1 silty clay and 3.2 silty clay. The support method for Section NO is determined to be downward slope + slope surface mesh spraying 1 + pile row 2 + pipe pile 3 + crown beam 8 + anchor cable 7 + pipe pile 3 inner mesh spraying 1; pile row 2 is 2 rows Cement soil mixing pile, L = 6.0m @ 0.35m; pipe pile 3 is PRC I500 (100) AB type pipe pile L = 12.0m @ 0.8m; anchor cable 7 is High-pressure jet grouting anchor L=21.0m@1.6m Tensile design value N=160kN Jet spraying section length 5.0m.

[0111] OP section: The soil layers from top to bottom are 1 plain fill, 2.2 silt, 2.3 silty clay, 2.4 silty clay, 2.5 silty clay, 3.1 silty clay and 3.2 silty clay. The OP section is determined to be supported by downward slope + 1 mesh sprayed concrete on the slope surface + 2 rows of piles + 4 supporting piles + 8 crown beams + 7 anchor cables + 1 mesh sprayed concrete on the inside of the 4 supporting piles; the 2 rows of piles are 2 rows. Cement soil mixing pile, L = 5.5m@0.35m; support pile 4 is a pre-guided hole Uniaxial cement soil mixing pile, L = 11.3m @ 0.9m, inserted H500 steel L = 12.0m; anchor cable 7 is High-pressure jet grouting anchor L=21.0m@1.8m Tensile design value N=160kN Jet spraying section length 5.0m.

[0112] PA section: The soil layers from top to bottom are 1 plain fill, 2.2 silt, 2.3 silty clay, 3.1 silty clay and 3.2 silty clay. The PA section is determined to be supported by downward slope + 1 mesh sprayed concrete on the slope + 2 rows of piles + 4 supporting piles + 8 crown beams + 1 mesh sprayed concrete on the inside of the 4 supporting piles; the pile row 2 is 2 rows Cement soil mixing pile, L = 5.5m@0.35m; support pile 4 is a pre-guided hole Uniaxial cement-soil mixing pile, L=11.3m@0.9m, inserted H500 steel L=12.0m.

[0113] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A deep foundation pit support, It is characterized in that The invention comprises a mesh sprayed concrete (1), a row of piles (2), a pipe pile (3), a supporting pile (4), an anchor cable (7) and a crown beam (8); the supporting piles (4) or the pipe piles (3) are arranged outside the underground foundation (9) of the building; the row of piles (2) are arranged outside some of the supporting piles (4) or the pipe piles (3); the crown beam (8) is arranged on some of the supporting piles (4) or the pipe piles (3); the anchor cable (7) is arranged on some of the crown beams (8); the anchor cable (7) is inclined downward and successively penetrates the supporting piles (4) or the pipe piles (3) and then penetrates the row of piles (2) to extend into the external soil layer; the mesh sprayed concrete (1) is arranged on the inner side of the pipe piles (3) or the supporting piles (4) close to the underground foundation (9) of the building; the soil layer at the top edge of the deep foundation pit slopes downward toward the underground foundation (9) of the building, and the mesh sprayed concrete (1) is arranged on the slope.

2. According to the deep foundation pit support described in claim 1, It is characterized in that Some of the pipe piles (3) or support piles (4) are arranged in two rows in parallel, and inter-pile reinforcements (5) are provided between the two rows of pipe piles (3) or between the two rows of support piles (4).

3. According to the deep foundation pit support described in claim 2, It is characterized in that The crown beam (8) comprises a first crown beam (8-1) and a second crown beam (8-2); the first crown beam (8-1) is arranged on the top of the pipe pile (3); the second crown beam (8-2) is arranged on the top of the support pile (4); a steel section (4-1) is embedded in the support pile (4); and the top of the steel section (4-1) passes through the second crown beam (8-2).

4. According to the deep foundation pit support of claim 3, It is characterized in that The head end of the steel strand (7-3) in the anchor cable (7) extending outside the crown beam (8) is fixed by an anchor (7-2) arranged on the side wall of the crown beam (8), and an anchor pad (7-1) is arranged between the anchor (7-2) and the crown beam (8).

5. According to the deep foundation pit support of claim 4, It is characterized in that The mesh sprayed concrete (1) comprises a steel plate mesh (1-1), transverse tie steel bars (1-2), steel bar soil nails (1-4) and sprayed concrete (1-5); the steel plate mesh (1-1) is fixedly arranged on the outside of the pipe pile (3) or the support pile (4); the transverse tie steel bars (1-2) are fixedly arranged on the outside of the steel plate mesh (1-1); the steel bar soil nails (1-4) are nailed between adjacent pipe piles (3) or the support piles (4); the sprayed concrete (1-5) is sprayed outside the transverse tie steel bars (1-2); and a plurality of drainage holes (1-3) are opened on the mesh sprayed concrete (1) outside the pipe pile (3).

6. According to claim 5, the deep foundation pit support It is characterized in that A water intercepting ditch (10) is provided at the outer edge of the top of the deep foundation pit, and a drainage ditch (11) is provided at the bottom of the deep foundation pit outside the underground foundation (9) of the building.

7. A deep foundation pit support construction process, It is characterized in that The steps include: Step 01: Design deep foundation pit support scheme: select different support methods according to the nature of the soil layer, groundwater conditions and the surrounding environment requirements of the deep foundation pit; Step 02: Site leveling: Level the ground in the construction area; Step 03, engineering pile construction: construction of row piles (2), construction of pipe piles (3) and construction of supporting piles (4); Step 04, deep foundation pit earthwork excavation construction: adopt layered construction, first carry out the first layer earthwork excavation, crown beam (8) construction, anchor cable (7) construction and mesh spraying concrete (1) construction; then carry out the next layer earthwork excavation, the next layer mesh spraying concrete (1) construction.

8. According to the deep foundation pit support construction process of claim 7, It is characterized in that The following steps are also included: Step 05, construction of intercepting ditch (10) and drainage ditch (11): an intercepting ditch (10) is opened at the outer edge of the top of the deep foundation pit, and a drainage ditch (11) is opened outside the underground foundation (9) of the building at the bottom of the deep foundation pit.

9. According to the deep foundation pit support construction process of claim 8, It is characterized in that The pipe pile (3) construction specifically includes: driving a single pipe pile into the soil layer according to the designed pile position; The construction of the support pile (4) specifically includes: using a rotary drilling rig or a long spiral drilling rig to pre-drill a hole and then backfilling with plain soil, using a strong support pile driver to mix in the hole to form a cement soil mixing pile, and finally implanting the steel (4-1) with the help of an insertion and extraction machine; The construction of the anchor cable (7) specifically includes: using a jet grouting drill to penetrate the silt layer at a construction angle of 30° downward; The mesh spraying concrete (1) construction specifically includes: when performing the slope mesh spraying concrete (1) construction: after mechanical excavation, the slope is repaired manually, short steel bars are vertically driven into the slope as a thickness mark, and spraying is performed from bottom to top, with the jet vertically spraying the surface; when performing the inter-pile mesh spraying concrete (1) construction: a steel plate mesh (1-1) and a transverse tie steel bar (1-2) are welded on the outside of a pipe pile (3) or a supporting pile (4), and steel bar soil nails (1-4) are driven in between adjacent pipe piles (3) or supporting piles (4), and then the spraying operation is performed.

10. According to the deep foundation pit support construction process of claim 9, It is characterized in that Deep foundation pit monitoring is carried out throughout the entire process of deep foundation pit construction.

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