CN111287198A - Supporting structure of soft soil foundation pit and construction method thereof - Google Patents
Supporting structure of soft soil foundation pit and construction method thereof Download PDFInfo
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- CN111287198A CN111287198A CN202010191530.4A CN202010191530A CN111287198A CN 111287198 A CN111287198 A CN 111287198A CN 202010191530 A CN202010191530 A CN 202010191530A CN 111287198 A CN111287198 A CN 111287198A
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- 239000002689 soil Substances 0.000 title claims abstract description 170
- 230000008093 supporting effect Effects 0.000 title claims abstract description 76
- 238000010276 construction Methods 0.000 title claims abstract description 54
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 221
- 239000010959 steel Substances 0.000 claims abstract description 221
- 230000003014 reinforcing effect Effects 0.000 claims abstract description 30
- 239000000835 fiber Substances 0.000 claims abstract description 19
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 16
- 238000009412 basement excavation Methods 0.000 claims description 18
- 238000000034 method Methods 0.000 claims description 17
- 238000005507 spraying Methods 0.000 claims description 14
- 230000008569 process Effects 0.000 claims description 11
- 238000013461 design Methods 0.000 claims description 3
- 238000012544 monitoring process Methods 0.000 claims description 3
- 238000003825 pressing Methods 0.000 claims description 3
- 238000012360 testing method Methods 0.000 claims description 3
- 230000009191 jumping Effects 0.000 claims description 2
- 238000005086 pumping Methods 0.000 claims description 2
- 241000587161 Gomphocarpus Species 0.000 abstract description 6
- 241000269793 Cryothenia peninsulae Species 0.000 abstract description 5
- 230000006872 improvement Effects 0.000 abstract description 3
- 101150054854 POU1F1 gene Proteins 0.000 description 55
- 230000002787 reinforcement Effects 0.000 description 4
- 230000015556 catabolic process Effects 0.000 description 3
- 230000007547 defect Effects 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 239000004568 cement Substances 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 230000003068 static effect Effects 0.000 description 2
- 229910001294 Reinforcing steel Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D17/00—Excavations; Bordering of excavations; Making embankments
- E02D17/02—Foundation pits
- E02D17/04—Bordering surfacing or stiffening the sides of foundation pits
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Abstract
The invention discloses a supporting structure of a soft soil foundation pit and a construction method thereof, relating to the technical field of soft soil foundation pit supporting, and the key points of the technical scheme are as follows: the foundation pit soil nail comprises a foundation pit, a plurality of soil nails, and a transverse closed channel steel and a vertical channel steel which connect the heads of the soil nails into a piece; the bottom end of the head part of the soil nail is sleeved with a square steel plate; the soil nails, the square steel plates and the transverse closed channel steel are locked by a plurality of nuts; an integral unloading platform is excavated in a layered and segmented manner on the soil body at the upper part of the foundation pit; a reinforcing mesh is laid on the slope of the integral unloading platform; the upper and lower slope surfaces of the foundation pit are sprayed with steel fiber concrete layers. This supporting construction jointly sets up the vertical channel-section steel in square steel sheet, the horizontal closed channel-section steel of pithead and the sloping through the soil nail, forms joint supporting construction, can increase the area of contact of supporting construction and foundation ditch pithead, overcomes the unable applied stress of soil nail, soil nail head and channel-section steel area of contact little and the shortcoming of puncturing easily, and this joint supporting construction overall rigidity is good, and impervious water proof performance is strong, can show improvement foundation ditch stability.
Description
Technical Field
The invention relates to the technical field of soft soil foundation pit supporting, in particular to a supporting structure of a soft soil foundation pit and a construction method thereof.
Background
The urbanization process of China is emerging, high-rise and super high-rise buildings and underground spaces are developed and utilized more and more, more and more foundation pit projects are generated inevitably, and geotechnical projects represented by foundation pit excavation and supporting are always concerned by people. From the development trend, ultra-deep and ultra-large foundation pits are more and more, and whether the selection of the foundation pit support and the construction method are scientific or not directly relates to the integral stability of the foundation pit and the safety of the surrounding environment. In order to ensure the safe construction of foundation pit engineering under complex conditions, the development concepts of green environmental protection construction and ecological civilized society construction are practiced, the requirements on the deep and large foundation pit supporting technology and construction method are higher and higher, and particularly, a new challenge is provided for the comprehensive supporting technology of the deep and large foundation pit under complex geological conditions.
At present, a cement mixing pile gravity type retaining wall is generally adopted as a supporting structure in a deep foundation pit in a soft soil area. Because the foundation ditch is darker, and the reinforcement width is bigger, then need be under construction multirow cement mixing pile, the engineering volume is huge, and construction speed is slow, and the cost is higher. In order to solve the technical problems in the prior art, the invention aims to provide a soft soil foundation pit supporting method combining soil nails and channel steel, an unloading platform is arranged by slope putting, and underground water control measures of dewatering wells and drainage ditches are taken inside and outside a pit to ensure the stability of the foundation pit and the safety of the surrounding environment. The supporting method is the optimization and extension of the existing soft soil foundation pit supporting technology, can adapt to different engineering geological conditions and construction environments, and has strong engineering practice significance.
Disclosure of Invention
The invention aims to provide a supporting structure of a soft soil foundation pit and a construction method thereof, wherein the supporting structure is formed by combining a square steel plate, a transverse closed channel steel and a vertical channel steel through soil nails, so that the contact area of the supporting structure and the pit wall of the foundation pit can be increased, and the defects that the soil nails cannot apply stress, the contact area of soil nail heads and the channel steel is small and the breakdown is easy are overcome; unloading the platform, and further reinforcing the supporting structure by using a reinforcing mesh and spraying steel fiber concrete; and underground water control measures of dewatering wells and drainage ditches are taken inside and outside the pit. The supporting structure has good overall stability and strong impermeability and water resistance; the construction method of the support has small construction disturbance and large operation space, and is suitable for soil layers with complex geological conditions, particularly for water-rich soft soil layers.
The technical purpose of the invention is realized by the following technical scheme: a supporting structure of a soft soil foundation pit comprises the foundation pit, a plurality of soil nails which are arranged at the middle lower part of the pit wall of the foundation pit at intervals, a transverse closed channel steel which is arranged along the pit wall of the foundation pit and a vertical channel steel which is statically pressed to the bottom of the foundation pit, wherein the soil nails are vertical to the pit wall of the foundation pit, and a square steel plate is sleeved at the bottom end of the head of each soil nail; the transverse closed channel steel is attached to the surface of the square steel plate, and the heads of the soil nails are connected into a piece by the transverse closed channel steel; the soil nails, the square steel plates and the transverse closed channel steel are locked into a whole through a plurality of nuts, and the nuts are respectively and fixedly connected with the heads of the soil nails; the soil body at the upper part of the foundation pit forms an integral unloading platform through layered and segmented excavation; a reinforcing mesh is laid on the slope surface of the integral unloading platform; and the upper and lower slope surfaces of the foundation pit are sprayed with steel fiber concrete spraying layers covering the reinforcing mesh and the transverse closed channel steel.
By adopting the technical scheme, in the process of supporting the foundation pit, firstly, leveling the ground, measuring and setting out wires, then setting relatively immovable control points and datum points according to field conditions, arranging a dewatering well outside the foundation pit, arranging a drainage ditch at the slope top of the foundation pit, and dewatering and draining; then excavating the foundation pit to a first-stage depth, and pre-spraying concrete with the thickness of 20mm on the slope surface of the excavated foundation pit to protect the slope surface of the excavated foundation pit; the soil nails which are applied to the wall of the foundation pit at intervals are combined with the square steel plate and the transverse closed channel steel, so that the contact area between the supporting structure and the wall of the foundation pit is conveniently increased, and the upper soil body of the foundation pit is conveniently and integrally reinforced; the vertical channel steel is convenient for reinforcing the soil body at the lower part of the foundation pit; the integral unloading platform arranged through slope relief is convenient for reducing the height of the pit wall of the foundation pit, increasing the stability of the foundation pit and ensuring the safety of the foundation pit, the supporting structure and the surrounding environment; the stability of the pit wall of the foundation pit is conveniently increased by the reinforcing mesh and the sprayed steel fiber concrete layer, and a combined supporting effect is formed by the plurality of soil nails, the transverse closed channel steel, the square steel plate and the vertical channel steel; according to the supporting structure of the soft soil foundation pit, the square steel plate, the transverse closed channel steel and the vertical channel steel are combined through the soil nails to form a combined supporting structure, so that the contact area of the supporting structure and the pit wall of the foundation pit can be increased, and the defects that the soil nails cannot apply stress, the contact area of the soil nail heads and the channel steel is small and breakdown is easy are overcome; meanwhile, the combined supporting structure has good integral rigidity and strong impermeability and water resistance, and can obviously improve the stability of the foundation pit.
The invention is further configured to: the quantity of soil nail is greater than 3, the interval between soil nail and the soil nail is 1.2 ~ 1.5 m.
Through adopting above-mentioned technical scheme, the quantity of soil nail is greater than 3, and the interval between soil nail and the soil nail is 1.2 ~ 1.5m, is convenient for guarantee soil nail and square steel sheet and the horizontal stability of closing the channel-section steel and uniting.
The invention is further configured to: the square steel plate is a hot-rolled steel plate, the thickness of the square steel plate is 1cm, and the side length of the square steel plate is 40-50 cm.
By adopting the technical scheme, the square steel plate is the hot-rolled steel plate, the thickness of the square steel plate is 1cm, the side length is 40-50 cm, and the contact area between the combined supporting structure formed by the soil nails, the square steel plate and the transverse closed channel steel and the pit wall of the foundation pit is increased conveniently.
The invention is further configured to: the diameter of the steel bar mesh is 8mm, and the grid size of the steel bar mesh is 200 multiplied by 200 mm.
By adopting the technical scheme, the operation of spraying the fiber concrete on the surface of the reinforcing mesh is facilitated by the reinforcing mesh with the diameter of the reinforcing steel bar of 8mm and the size of the grid of 200 multiplied by 200 mm.
The invention is further configured to: and the excavation depth of the vertical channel steel to the next stage of foundation pit is not less than 50 cm.
By adopting the technical scheme, the depth of the vertical channel steel to the next level of foundation pit excavation is not less than 50cm, so that the horizontal closed channel steel, the soil nails and the vertical channel steel can be conveniently supported in a combined manner.
The invention is further configured to: the transverse closed channel steel (3) and the vertical channel steel (4) are 32C channel steel.
Through adopting above-mentioned technical scheme, transversely seal the channel-section steel and all adopt the 32C channel-section steel with vertical channel-section steel, be convenient for guarantee ensure soil nail, transversely seal the stability that forms joint supporting construction between channel-section steel, square steel plate and the vertical channel-section steel.
A construction method of a soft soil foundation pit support comprises the following steps:
s1, leveling a field, measuring and setting out wires, setting relatively immovable control points and reference points according to field conditions, arranging a dewatering well outside the foundation pit, and arranging a drainage ditch on the slope top of the foundation pit for dewatering and drainage;
s2, excavating the foundation pit to a first-level depth, and pre-spraying concrete with the thickness of 20mm on the slope surface of the excavated foundation pit to protect the slope surface of the foundation pit; arranging a drain hole on the slope surface of the foundation pit, arranging a temporary drainage ditch and a water collection well at the bottom of the foundation pit, and timely pumping and draining the collected water in the foundation pit;
s3, before large-area construction, not less than three soil nails are constructed in an actual soil layer to perform a pulling resistance test, and the construction process of the soil nails is determined;
s4, constructing a soil nailing wall at the middle lower part of the excavated foundation pit wall, constructing more than 3 soil nails with the distance of 1.2-1.5 m at intervals at the middle lower part of the foundation pit wall according to the construction process of the soil nails determined in the step S3, sleeving square steel plates with the thickness of 1cm and the side length of 40-50 cm below soil nail heads, arranging transverse closed channel steel along the foundation pit wall, connecting the soil nail heads into one piece, locking the soil nails, the square steel plates and the transverse closed channel steel together through nuts, and integrally reinforcing the soil body at the upper part of the foundation pit;
s5, statically pressing vertical channel steel at the bottom of the foundation pit, wherein the depth of the vertical channel steel to the excavation depth of the next stage of foundation pit is not less than 50cm, so that the transverse closed channel steel, the soil nails and the vertical channel steel form a combined support, and the soil body at the lower part of the foundation pit is integrally reinforced;
s6, jumping, digging and unloading the upper soil body of the foundation pit wall by adopting a mode of combining machinery with manual digging to form a soil outlet; then gradually carrying out layered and segmented excavation to form an integral unloading platform, paving the reinforcing mesh on the integral unloading platform, then carrying out integral spraying of steel fiber concrete on the upper and lower slope surfaces of the foundation pit, covering the reinforcing mesh on the slope surface of the integral unloading platform and the transverse closed channel steel of the slope surface of the foundation pit, and enabling the transverse closed channel steel, the vertical channel steel, the soil nails, the reinforcing mesh and the sprayed steel fiber concrete to form a combined supporting structure;
and S7, monitoring the stress and deformation conditions of the pit wall of the foundation pit and the combined supporting structure, and performing next-stage slope excavation and supporting until the design depth is reached after the requirements are met.
The invention is further configured to: the diameter of the steel bar mesh in the step S6 is 8mm, and the mesh size of the steel bar mesh is 200 × 200 mm.
The invention is further configured to: and the transverse closing channel steel in the step S4 and the vertical channel steel in the step S5 are both 32C channel steel.
In conclusion, the invention has the following beneficial effects: the soil nails which are applied to the wall of the foundation pit at intervals are combined with the square steel plate and the transverse closed channel steel, so that the contact area between the supporting structure and the wall of the foundation pit is conveniently increased, and the upper soil body of the foundation pit is conveniently and integrally reinforced; the vertical channel steel is convenient for reinforcing the soil body at the lower part of the foundation pit; the integral unloading platform arranged through slope relief is convenient for reducing the height of the pit wall of the foundation pit, increasing the stability of the foundation pit and ensuring the safety of the foundation pit and the surrounding environment; the stability of the pit wall of the foundation pit is conveniently increased by the reinforcing mesh and the sprayed steel fiber concrete layer, and a combined supporting effect is formed by the plurality of soil nails, the transverse closed channel steel, the square steel plate and the vertical channel steel; this supporting construction of weak soil foundation ditch through soil nail combination square steel sheet, horizontal closed channel-section steel and vertical channel-section steel, forms joint supporting construction, can increase the area of contact of supporting construction and foundation ditch pithead, overcomes the unable applied stress of soil nail, soil nail head and channel-section steel area of contact little and the shortcoming of puncturing easily, and this joint supporting construction overall rigidity is good, and impervious water proof performance is strong, can show improvement foundation ditch stability.
Drawings
FIG. 1 is a schematic structural view in example 1 of the present invention;
fig. 2 is a schematic structural view of a slope-releasing forming unloading platform in embodiment 1 of the present invention;
fig. 3 is a flowchart in embodiment 2 of the present invention.
In the figure: 1. a foundation pit; 2. soil nailing; 3. horizontally closing the channel steel; 4. vertical channel steel; 5. a square steel plate; 6. a nut; 7. an integral unloading platform; 8. a reinforcing mesh; 9. and spraying a steel fiber concrete layer.
Detailed Description
The present invention is described in further detail below with reference to figures 1-3.
Example 1: the utility model provides a supporting construction of weak soil foundation ditch, as shown in fig. 1 and fig. 2, execute a plurality of soil nails 2 of lower part in 1 hole wall of foundation ditch, along the horizontal closed channel-section steel 3 and the vertical channel-section steel 4 of static pressure to the foundation ditch 1 hole bottom of 1 hole wall setting of foundation ditch 1, soil nail 2 is perpendicular with 1 hole wall of foundation ditch, and 2 head bottom covers of soil nail are equipped with square steel sheet 5 including foundation ditch 1, interval. The transverse closed channel steel 3 is attached to the surface of the square steel plate 5, and the heads of the soil nails 2 are connected into a whole through the transverse closed channel steel 3. Soil nail 2, square steel plate 5 and horizontal closed channel-section steel 3 lock as a whole through a plurality of nuts 6, a plurality of nuts 6 respectively with 2 head fixed connection of each soil nail. The upper soil body of the foundation pit 1 is formed with an integral unloading platform 7 through layered and segmented excavation. And a reinforcing mesh 8 is laid on the slope surface of the integral unloading platform 7. The upper and lower slope surfaces of the foundation pit 1 are sprayed with a sprayed steel fiber concrete layer 9 which covers the reinforcing mesh 8 and the transverse closed channel steel 3.
In the embodiment, in the process of supporting the foundation pit 1, firstly, the ground is leveled, the measurement and the paying-off are carried out, then, relatively immovable control points and datum points are set according to the field conditions, a dewatering well is arranged outside the foundation pit 1, a drainage ditch is arranged on the slope top of the foundation pit 1, and dewatering and drainage are carried out. And then excavating the foundation pit 1 to the first-stage depth, and pre-spraying concrete with the thickness of 20mm on the slope surface of the excavated foundation pit 1 to protect the slope surface of the excavated foundation pit 1. The soil nails 2 which are arranged on the wall of the foundation pit 1 at intervals are combined with the square steel plate 5 and the transverse closed channel steel 3, so that the contact area between the supporting structure and the wall of the foundation pit 1 is increased, and the upper soil body of the foundation pit 1 is integrally reinforced. Through vertical channel-section steel 4, be convenient for consolidate the soil body of foundation ditch 1 lower part. Through the integral unloading platform 7 arranged on the slope, the height of the pit wall of the foundation pit 1 is convenient to reduce, the stability of the foundation pit 1 is improved, and the safety of the foundation pit 1, a supporting structure and the surrounding environment is ensured. Through the reinforcing mesh 8 and the sprayed steel fiber concrete layer 9, the stability of the pit wall of the foundation pit 1 is convenient to increase, and a combined supporting effect is formed by the plurality of soil nails 2, the transverse closed channel steel 3, the square steel plate 5 and the vertical channel steel 4. This supporting construction of weak soil foundation ditch 1 combines square steel sheet 5, horizontal closed channel-section steel 3 and vertical channel-section steel 4 through soil nail 2, forms joint supporting construction, can increase the area of contact of supporting construction and foundation ditch 1 pithead, overcomes the shortcoming that soil nail 2 can't exert stress, 2 heads of soil nail and channel-section steel area of contact are little and puncture easily. Meanwhile, the combined supporting structure is good in overall rigidity and strong in impermeability and water resistance, and the stability of the foundation pit 1 can be obviously improved.
The number of the soil nails 2 is more than 3, and the distance between the soil nails 2 and the soil nails 2 is 1.2-1.5 m.
In this embodiment, the quantity of soil nail 2 is greater than 3, and the interval between soil nail 2 and the soil nail 2 is 1.2 ~ 1.5m, is convenient for guarantee soil nail 2 and square steel plate 5 and the stability that transversely seals channel-section steel 3 and unite.
The square steel plate 5 is a hot-rolled steel plate, the thickness of the square steel plate 5 is 1cm, and the side length of the square steel plate 5 is 40-50 cm.
In the embodiment, the square steel plate 5 is a hot-rolled steel plate, the thickness of the square steel plate 5 is 1cm, and the side length is 40-50 cm, so that the contact area between the combined supporting structure formed by the soil nails 2, the square steel plate 5 and the transverse closed channel steel 3 and the pit wall of the foundation pit 1 is increased conveniently.
The diameter of the steel bar net 8 is 8mm, and the grid size of the steel bar net 8 is 200 x 200 mm.
In this embodiment, the operation of spraying the fiber concrete on the surface of the mesh reinforcement 8 is facilitated by the mesh reinforcement 8 having a mesh size of 200 × 200mm and a reinforcement diameter of 8 mm.
The excavation depth of the vertical channel steel 4 to the next stage of foundation pit 1 is not less than 50 cm.
In this embodiment, vertical channel-section steel 4 is no less than 50cm to below the 1 excavation depth of next grade foundation ditch, is convenient for ensure to form the joint support between horizontal closed channel-section steel 3, soil nail 2 and the vertical channel-section steel 4.
The transverse closed channel steel 3 and the vertical channel steel 4 are 32C channel steel.
In this embodiment, horizontal closed channel-section steel 3 and vertical channel-section steel 4 all adopt the 32C channel-section steel, are convenient for guarantee to ensure that soil nail 2, horizontal closed channel-section steel 3, square steel plate 5 and vertical channel-section steel 4 between form the stability of joint supporting construction.
Example 2: a construction method of a soft soil foundation pit support, as shown in fig. 3, includes the following steps:
s1, leveling the ground, measuring and setting out the line, setting relatively immovable control points and reference points according to field conditions, arranging a precipitation well outside the foundation pit 1, and arranging a drainage ditch at the top of the foundation pit 1 to perform precipitation and drainage.
S2, excavating the foundation pit 1 to the first-level depth, and pre-spraying concrete with the thickness of 20mm on the slope surface of the excavated foundation pit 1 to protect the slope surface of the foundation pit 1. Set up the outlet at foundation ditch 1 domatic to set up interim escape canal and collector well in foundation ditch 1 bottom, in time the pump drainage with catchmenting in the foundation ditch 1.
And S3, before the large-area construction, not less than three soil nails 2 are constructed in the actual soil layer to perform the uplift resistance test, and the construction process of the soil nails 2 is determined.
S4, constructing a soil nail 2 wall on the middle lower part of the excavated foundation pit 1 wall, constructing more than 3 soil nails 2 with the distance of 1.2-1.5 m on the middle lower part of the foundation pit 1 wall at intervals according to the construction process of the soil nails 2 determined in the step S3, sleeving square steel plates 5 with the thickness of 1cm and the side length of 40-50 cm under the heads of the soil nails 2, then arranging transverse closed channel steel 3 along the foundation pit 1 wall, connecting the heads of the soil nails 2 into one piece, locking the soil nails 2, the square steel plates 5 and the transverse closed channel steel 3 together through nuts 6, and integrally reinforcing the upper soil body of the foundation pit 1.
S5, static pressing is conducted on the vertical channel steel 4 at the bottom of the foundation pit 1, the depth from the vertical channel steel 4 to the next foundation pit 1 is not less than 50cm, the transverse closed channel steel 3, the soil nails 2 and the vertical channel steel 4 form combined support, and the soil body on the lower portion of the foundation pit 1 is integrally reinforced.
And S6, adopting a mode of combining machinery and manual excavation to jump, dig and unload the upper soil body on the wall of the foundation pit 1 to form a soil outlet. And then gradually carrying out layered and segmented excavation to form an integral unloading platform 7, paving the reinforcing mesh 8 on the integral unloading platform 7, integrally spraying steel fiber concrete on the upper and lower slope surfaces of the foundation pit 1, covering the reinforcing mesh 8 on the slope surface of the integral unloading platform 7 and the transverse closed channel steel 3 on the slope surface of the foundation pit 1, and enabling the transverse closed channel steel 3, the vertical channel steel 4, the soil nails 2, the reinforcing mesh 8 and the sprayed steel fiber concrete to form a combined supporting structure.
And S7, monitoring the stress and deformation conditions of the pit wall of the foundation pit 1 and the combined supporting structure, and performing next-stage slope excavation and supporting until the design depth is reached after the requirements are met.
In the construction method of the soft soil foundation pit support, the soil body on the upper part of the foundation pit 1 is reinforced through the soil nails 2 and the square steel plates 5 and the transverse closed channel steel 3, the soil body on the lower part of the foundation pit 1 is reinforced through the vertical channel steel 4, and the integral unloading platform 7 is arranged through slope putting, so that the height of the pit wall of the foundation pit 1 can be reduced, and the purposes of unloading and increasing the integral stability of the foundation pit 1 are achieved. The stability of the pit wall of the foundation pit 1 is improved through the reinforcing mesh 8 and the sprayed steel fiber concrete. Meanwhile, a dewatering well and a drainage ditch are arranged inside and outside the foundation pit 1, and drainage holes are formed in the slope surface, so that underground water can be conveniently controlled. The supporting method of the foundation pit 1 has the advantages of small construction disturbance, large integral rigidity of the combined supporting structure and good impermeability and water resistance. The contact area of the supporting structure of the soil nail 2 wall combined square steel plate 5 and the transverse closed channel steel 3 and the wall of the foundation pit 1 is greatly increased, and the defects that the soil nail 2 cannot apply stress, the contact area of the soil nail 2 head and the channel steel is small, and the breakdown is easy are overcome. Meanwhile, the construction method of the support has the advantages of large operation space and good overall stress performance of the support structure, is suitable for water-rich soft soil layers with complex geological conditions and high permeability, can flexibly adjust the process parameters such as the size of the steel plate, the distance between the soil nails 2, the distance between the channel steel and the like according to actual conditions, and has wide application range.
In step S6, the diameter of the steel bar net 8 is 8mm, and the mesh size of the steel bar net 8 is 200 × 200 mm.
And the transverse closing channel steel 3 in the step S4 and the vertical channel steel 4 in the step S5 both adopt 32C channel steel.
The working principle is as follows: in the process of supporting the foundation pit 1, firstly, leveling the ground, measuring and setting off lines, then setting relatively immovable control points and datum points according to field conditions, arranging a dewatering well outside the foundation pit 1, and arranging a drainage ditch at the top of the foundation pit 1 for dewatering. And then excavating the foundation pit 1 to the first-stage depth, and pre-spraying concrete with the thickness of 20mm on the slope surface of the excavated foundation pit 1 to protect the slope surface of the excavated foundation pit 1. The soil nails 2 which are arranged on the wall of the foundation pit 1 at intervals are combined with the square steel plate 5 and the transverse closed channel steel 3, so that the contact area between the supporting structure and the wall of the foundation pit 1 is increased, and the upper soil body of the foundation pit 1 is integrally reinforced. Through vertical channel-section steel 4, be convenient for consolidate the soil body of foundation ditch 1 lower part. Through the integral unloading platform 7 arranged on the slope, the height of the pit wall of the foundation pit 1 is convenient to reduce, the stability of the foundation pit 1 is improved, and the safety of the foundation pit 1, a supporting structure and the surrounding environment is ensured. Through the reinforcing mesh 8 and the sprayed steel fiber concrete layer 9, the stability of the pit wall of the foundation pit 1 is convenient to increase, and a combined supporting effect is formed by the plurality of soil nails 2, the transverse closed channel steel 3, the square steel plate 5 and the vertical channel steel 4. This supporting construction of weak soil foundation ditch 1, through soil nail 2 combination square steel sheet 5, horizontal closed channel-section steel 3 and vertical channel-section steel 4, form joint supporting construction, increase the area of contact of supporting construction and foundation ditch 1 pithead, overcome the unable applied stress of soil nail 2, soil nail 2 head and channel-section steel area of contact little and the shortcoming of puncturing easily, this joint supporting construction overall rigidity is good, impervious water proof performance is strong, can show improvement foundation ditch stability.
The present embodiment is only for explaining the present invention, and it is not limited to the present invention, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present invention.
Claims (9)
1. The utility model provides a supporting construction of weak soil foundation ditch, characterized by: the soil nail fixing device comprises a foundation pit (1), a plurality of soil nails (2) which are applied to the middle lower part of the pit wall of the foundation pit (1) at intervals, transverse closed channel steel (3) arranged along the pit wall of the foundation pit (1) and vertical channel steel (4) which is statically pressed to the pit bottom of the foundation pit (1), wherein the soil nails (2) are vertical to the pit wall of the foundation pit (1), and a square steel plate (5) is sleeved at the bottom end of the head part of each soil nail (2); the transverse closed channel steel (3) is attached to the surface of the square steel plate (5), and the heads of the soil nails (2) are connected into a whole by the transverse closed channel steel (3); the soil nails (2), the square steel plates (5) and the transverse closed channel steel (3) are locked into a whole through a plurality of nuts (6), and the nuts (6) are respectively and fixedly connected with the heads of the soil nails (2); an integral unloading platform (7) is formed on the soil body at the upper part of the foundation pit through layered and segmented excavation; a reinforcing mesh (8) is laid on the slope surface of the integral unloading platform (7); the upper and lower slope surfaces of the foundation pit (1) are sprayed with steel fiber concrete sprayed layers (9) covering the steel mesh (8) and the transverse closed channel steel (3).
2. A supporting construction for a soft soil foundation pit according to claim 1, characterised in that: the number of the soil nails (2) is more than 3, and the distance between the soil nails (2) and the soil nails (2) is 1.2-1.5 m.
3. A supporting construction for a soft soil foundation pit according to claim 1, characterised in that: the square steel plate (5) is a hot-rolled steel plate, the thickness of the square steel plate (5) is 1cm, and the side length of the square steel plate (5) is 40-50 cm.
4. A supporting construction for a soft soil foundation pit according to claim 1, characterised in that: the diameter of the steel bar mesh (8) is 8mm, and the grid size of the steel bar mesh (8) is 200 multiplied by 200 mm.
5. A supporting construction for a soft soil foundation pit according to claim 1, characterised in that: and the excavation depth from the vertical channel steel (4) to the next stage of foundation pit (1) is not less than 50 cm.
6. A supporting construction for a soft soil foundation pit according to claim 1, characterised in that: the transverse closed channel steel (3) and the vertical channel steel (4) are 32C channel steel.
7. A construction method of a soft soil foundation pit support is characterized by comprising the following steps: the method comprises the following steps:
s1, leveling a field, measuring and setting out, setting relatively immovable control points and reference points according to field conditions, arranging a dewatering well outside the foundation pit (1), and arranging a drainage ditch at the slope top of the foundation pit (1) for dewatering and drainage;
s2, excavating the foundation pit (1) to a first-level depth, and pre-spraying concrete with the thickness of 20mm on the slope surface of the excavated foundation pit (1) to protect the slope surface of the foundation pit (1); arranging drain holes on the slope surface of the foundation pit (1), arranging a temporary drainage ditch and a water collection well at the bottom of the foundation pit (1), and timely pumping and draining collected water in the foundation pit (1);
s3, before large-area construction, not less than three soil nails (2) are constructed in an actual soil layer to perform a pulling resistance test, and the construction process of the soil nails (2) is determined;
s4, constructing a soil nail (2) wall at the middle lower part of the wall of the excavated foundation pit (1), constructing a plurality of soil nails (2) with the distance of 1.2-1.5 m at intervals at the middle lower part of the wall of the foundation pit (1) according to the construction process of the soil nails (2) determined in the step S3, sleeving a square steel plate (5) with the thickness of 1cm and the side length of 40-50 cm on the head part of each soil nail (2), arranging transverse closed channel steel (3) attached to the surface of the square steel plate (5) along the wall of the foundation pit (1), connecting the head parts of the soil nails (2) into a whole, locking the soil nails (2), the square steel plate (5) and the transverse closed channel steel (3) together through nuts (6), and integrally reinforcing the soil body at the upper part of the foundation pit (1);
s5, statically pressing the vertical channel steel (4) at the bottom of the foundation pit (1), wherein the depth from the vertical channel steel (4) to the excavation depth of the next foundation pit (1) is not less than 50cm, so that the transverse closed channel steel (3), the soil nails (2) and the vertical channel steel (4) form a combined support, and the soil body at the lower part of the foundation pit (1) is integrally reinforced;
s6, jumping, digging and unloading the upper soil body of the wall of the foundation pit (1) by adopting a mode of combining machinery with manual digging to form a soil outlet; then gradually carrying out layered and segmented excavation to form an integral unloading platform (7), laying a reinforcing mesh (8) on the integral unloading platform (7), integrally spraying steel fiber concrete on the upper and lower slope surfaces of the foundation pit (1), covering the reinforcing mesh (8) on the slope surface of the integral unloading platform (7) and the transverse closed channel steel (3) on the slope surface of the foundation pit (1), and enabling the transverse closed channel steel (3), the vertical channel steel (4), the soil nails (2), the reinforcing mesh (8) and the sprayed steel fiber concrete to form a combined supporting structure;
s7, monitoring the stress and deformation conditions of the pit wall of the foundation pit (1) and the combined supporting structure, and performing next-stage slope excavation and supporting until the design depth is reached after the requirements are met.
8. A method of constructing a soft soil foundation pit support according to claim 7, wherein: the diameter of the steel bar mesh (8) in the step S6 is 8mm, and the mesh size of the steel bar mesh (8) is 200 × 200 mm.
9. A method of constructing a soft soil foundation pit support according to claim 7, wherein: and (3) adopting 32C channel steel for both the transverse closed channel steel (3) in the step S4 and the vertical channel steel (4) in the step S5.
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