CN111456019A - Safe construction method for foundation pit excavation - Google Patents
Safe construction method for foundation pit excavation Download PDFInfo
- Publication number
- CN111456019A CN111456019A CN202010276763.4A CN202010276763A CN111456019A CN 111456019 A CN111456019 A CN 111456019A CN 202010276763 A CN202010276763 A CN 202010276763A CN 111456019 A CN111456019 A CN 111456019A
- Authority
- CN
- China
- Prior art keywords
- excavation
- foundation pit
- pile
- layer
- concrete
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- 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
-
- 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
-
- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D33/00—Testing foundations or foundation structures
-
- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D5/00—Bulkheads, piles, or other structural elements specially adapted to foundation engineering
- E02D5/22—Piles
- E02D5/34—Concrete or concrete-like piles cast in position ; Apparatus for making same
- E02D5/38—Concrete or concrete-like piles cast in position ; Apparatus for making same making by use of mould-pipes or other moulds
-
- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04G—SCAFFOLDING; FORMS; SHUTTERING; BUILDING IMPLEMENTS OR AIDS, OR THEIR USE; HANDLING BUILDING MATERIALS ON THE SITE; REPAIRING, BREAKING-UP OR OTHER WORK ON EXISTING BUILDINGS
- E04G21/00—Preparing, conveying, or working-up building materials or building elements in situ; Other devices or measures for constructional work
- E04G21/32—Safety or protective measures for persons during the construction of buildings
- E04G21/3204—Safety or protective measures for persons during the construction of buildings against falling down
-
- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D2300/00—Materials
- E02D2300/0004—Synthetics
- E02D2300/0018—Cement used as binder
- E02D2300/002—Concrete
Landscapes
- Engineering & Computer Science (AREA)
- Structural Engineering (AREA)
- Mining & Mineral Resources (AREA)
- Civil Engineering (AREA)
- Life Sciences & Earth Sciences (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Paleontology (AREA)
- General Engineering & Computer Science (AREA)
- Architecture (AREA)
- Mechanical Engineering (AREA)
- Piles And Underground Anchors (AREA)
Abstract
The invention relates to a safe construction method for foundation pit excavation. The method comprises the following steps of (1) releasing a foundation pit excavation boundary line on the original ground according to a construction drawing, measuring the elevation and determining the excavation depth; (2) excavating a surface layer of the foundation pit by using a backhoe excavator, and directly transporting the earthwork obtained after excavation outwards by using a self-dumping vehicle; (3) excavating the foundation pit layer by layer in a layered excavation mode, wherein the excavation depth of each layer is 1.5-2 m; (4) placing slopes on two sides in the excavation process of the foundation pit, wherein the slope is 60-75 degrees, and carrying out soil nailing wall type supporting on the placed slopes after each layer of excavation is finished; (5) cleaning the bottom of the substrate with the residual 0.2-0.3m by manual work; (6) performing cast-in-place pile construction on the foundation of the foundation pit; (7) and constructing a concrete structure cushion layer on the foundation of the foundation pit. The construction method provided by the invention adopts a mode of excavation of the foundation pit layer by layer to excavate layer by layer, and the slope surface is supported in time after each layer of excavation is finished, so that the construction safety is improved.
Description
Technical Field
The invention belongs to the technical field of comprehensive pipe gallery construction, and particularly relates to a safe construction method for foundation pit excavation.
Background
The open cut method is an underground engineering construction method which firstly excavates the ground, builds a lining under the open air condition and then covers and backfills the ground, and is mainly used for shallow tunnels. The open cut method is the most basic and common construction method in the soft soil underground engineering construction, and the open cut construction method is usually adopted in the construction of the comprehensive pipe gallery. According to the form of the enclosure structure of the engineering foundation pit, the excavation method comprises direct layered excavation, excavation with side wall supports and the like, and the excavation method can be selected according to specific conditions in engineering. In a foundation pit without support, the principle of 'layered excavation of earthwork and pouring of a cushion layer along with excavation' is followed in the excavation of earthwork; in a foundation pit with a support, the principle of 'supporting by slotting, digging after supporting, layered digging and strictly over digging' is followed, and a cushion layer is dug along with the digging and pouring. In addition, the sequence and method of earth excavation must be consistent with the design conditions. And observing and monitoring the supporting structure and the surrounding environment during excavation of the foundation pit earthwork, and if abnormal conditions occur, timely processing, and continuing construction after the normal conditions are recovered.
The common equipment in the open cut construction process is an excavator, a bulldozer, a dump truck and the like, earthwork obtained by excavating a foundation pit is transferred to other places in a hoisting mode or a vehicle conveying mode, whether a hoisting tool and a rope are firm or not and people cannot stand below a hoisting bucket are checked in the former mode, soil piles are separated from the edge of the pit for a certain distance in the latter mode so as to prevent collapse of the pit wall, the road is leveled in advance, and a one-way road is adopted as far as possible so as to avoid collision back and forth.
Due to the characteristics of open cut construction, in the process of layered excavation, the side slope of the foundation pit is easy to collapse, so that engineering danger is caused. Particularly, under the conditions of construction in a soft soil layer and in rainy days, the phenomenon of collapse of the foundation pit slope is more frequent. Therefore, the steps of the foundation pit excavation construction method need to be optimally designed, and the safety of the construction process is improved.
Disclosure of Invention
The invention provides a safe construction method for foundation pit excavation for solving the technical problems in the prior art, and the safety of the construction process is improved.
The technical scheme adopted by the invention for solving the technical problems in the prior art is as follows: a safe construction method for foundation pit excavation comprises the following steps of (1) releasing a foundation pit excavation boundary line on an original ground surface according to a construction drawing, measuring an elevation and determining an excavation depth; (2) excavating a surface layer of the foundation pit by using a backhoe excavator, and directly transporting the earthwork obtained after excavation outwards by using a self-dumping vehicle; (3) excavating the foundation pit layer by layer in a layered excavation mode, wherein the excavation depth of each layer is 1.5-2 m; (4) placing slopes on two sides in the excavation process of the foundation pit, wherein the slope is 60-75 degrees, and carrying out soil nailing wall type supporting on the placed slopes after each layer of excavation is finished; (5) cleaning the bottom of the substrate with the residual 0.2-0.3m by manual work; (6) performing cast-in-place pile construction on the foundation of the foundation pit; (7) and constructing a concrete structure cushion layer on the foundation of the foundation pit.
The invention has the advantages and positive effects that: compared with the existing construction method, the method adopts the layered excavation construction process of the foundation pit, namely, the excavation surface layer is excavated first and then the foundation pit is excavated downwards layer by layer, so that the operability in the construction process is improved, and the construction safety is improved. Through putting the slope in the both sides of foundation ditch in the excavation construction to in time carrying out the bank protection of side slope after every layer excavation finishes, effectively avoided the phenomenon that foundation ditch both sides collapse, under the condition of the comparatively soft area of soil property and overcast and rainy weather construction, this construction technology has greatly promoted the security when guaranteeing each item index requirement of foundation ditch excavation construction.
Preferably: a step of edge protection is also arranged between the steps (1) and (2), and the step is used around the foundation pit
The steel pipe is driven into the ground by 1000mm deep to serve as a vertical rod of a protective railing, the distance between the steel pipe and the edge of the foundation pit is 500mm, and the protection is realizedThe handrail consists of an upper cross bar, a middle cross bar and a lower cross bar and the upright posts, wherein the distance between the cross bars is 0.6m, the ground clearance of the upper post is 1.3m, the ground clearance of the lower post is 0.1m, and the distance between the upright posts is 2 m; and hanging a safety prompt slogan and a safety warning board at the periphery of the foundation pit.
Preferably: the step of the soil nailing wall support in the step (4) is that 1) the side slope is trimmed, the side slope is cleaned manually to ensure the flatness of the sprayed concrete surface layer, and the wire hanging positioning is carried out in the process; for the side slope with large water content of the soil layer, a horizontal drainage pipe with the length of 400-600mm and the diameter of not less than 40mm is inserted into the back of the supporting surface layer to wrap the filter screen, the outer end of the horizontal drainage pipe extends out of the supporting surface layer at the interval of 2m, and accumulated water after the concrete surface layer is sprayed is drained away; 2) arranging the holes, namely, arranging the positions of each soil nail by a measurer according to a design drawing, wherein the soil nail steel bars are arranged according to a quincunx by adopting C22 or C25, the horizontal distance is 1.5m or 2.0m, and the vertical distance is 1.5 m; 3) manufacturing and placing soil nails, mounting a soil nail anchor rod after pre-drilling holes on the soil nails, wherein the soil nail anchor rod adopts A8 steel bars as a bracket, and a pipe head is fully welded with one side of a C22 soil nail hook by using a C16 reinforcing rib and is welded on a steel bar net; 4) grouting, namely placing the soil nail steel bars into the holes after hole forming, wherein the grouting adopts P.SA32.5 cement, the water cement ratio is 0.5-0.55, and the strength of slurry is not lower than 20 MPa; during grouting, an early strength agent and an expanding agent are added to improve the early strength of a grouting body and increase the friction force between the grouting body and a soil body on a hole wall; 5) hanging net and anchor head installation, reinforcing bar net piece
150mm × mm) is fixed by steel bars inserted into soil, the gap between the steel bars and a slope surface is 3-4cm, the upper part, the lower part, the left part and the right part are lapped and bound one by one when lapping is carried out, the lapping length is more than 30cm and is not less than two points are spot welded, a steel bar net sheet is provided with horizontal fixing bars, 6) concrete is sprayed, dry concrete is sprayed, the dry concrete is manually stirred on site, P.S. A32.5 cement, fine sand and 5-10mm mechanically-broken stone are used, an accelerating agent is added in a collapse-prone area to improve the surface concrete setting speed, side slope hanging nets are sprayed with concrete for protection, meanwhile, horizontal reinforcing bars are arranged, the vertical distance is 1m, the horizontal reinforcing bars are welded with the steel bars implanted into the side slope soil body and are firmly connected with the steel bar nets, the strength grade.
Preferably: the construction of the cast-in-place pile in the step (6) comprises the steps of 1) preparing for construction, leveling the field, removing sundries, replacing soft soil, compacting by ramming and uniformly planning a mud pit; 2) measuring and paying off, namely determining the pile position by using a total station according to a construction drawing and a field lead control point, and driving a timber pile; leading the pile to the periphery by a cross method and using short steel bars to make a pile protector; 3) embedding a pile casing, wherein the pile casing is an integral steel pile casing welded by a steel plate with the plate thickness of 4-6mm, and the diameter and the burial depth of the pile casing are determined according to a design drawing; the excavation diameter is 0.2-0.4m larger than the pile casing, and the depth of the pit bottom is as high as the bottom of the pile casing; 2 overflow ports are arranged on the pile casing, when the pile casing is buried, the center of the pile casing is superposed with the center of the pile, the deviation is less than or equal to 20mm, the deviation of the verticality of the pile casing is kept to be less than or equal to 1%, and the top of the pile casing is 0.3m higher than the ground; 4) preparing slurry; 5) drilling to form a hole, wherein during drilling, mud is injected while drilling to protect the wall, the mud surface is always not lower than 0.5m below the top of the protective cylinder, the verticality is detected at any time during drilling, and the mud specific gravity is controlled within 1.25 after hole forming; 6) cleaning holes, cleaning holes for the first time: after pile holes are formed, performing first hole cleaning before the reinforcement cage is inserted into the holes, removing drilling slag by using an in-hole drilling bucket, and if the settling time is long, performing turbid water circulation by using a water pump to enable the density to reach about 1.2; cleaning the hole for the second time: after the steel reinforcement cage and the guide pipe are placed, secondary hole cleaning is carried out by an air lift method, and the time for secondary hole cleaning is not less than 30 min; 7) manufacturing and installing a reinforcement cage, namely manufacturing the reinforcement cage and placing the reinforcement cage into the pile hole; 8) underwater concrete pouring, and pouring concrete into the pile hole; 9) and (3) pile detection, after the construction is finished, carrying out a small strain test and a large strain test of 5-10% of the total number of pile foundations on the engineering pile, and checking the pile forming effect of the single pile.
Preferably: the concrete structure cushion layer construction in the step (7) comprises the steps of 1) checking a groove of the foundation pit, cleaning up the floating soil on the surface of the foundation pit, enabling elevation and surface flatness to meet design requirements and standard regulations, carrying out sectional groove checking according to a program, carrying out foundation treatment on the found soil layer which does not meet the design requirements according to the opinions of a design unit, and after the treatment is finished, asking a supervision unit to check and accept and handling hidden inspection records; 2) retesting and measuring lofting, retesting the size and the position deviation of the foundation pit excavation after the foundation pit excavation is finished, wherein the size and the position deviation of the foundation pit excavation should meet the construction and specification requirements; 3) the method comprises the following steps of (1) formwork erecting and elevation retest, wherein a wood beam is used as a side formwork of the engineering cushion formwork and is kept stable, and a level gauge is used for retesting the elevation so as to prevent elevation errors after the cushion is poured; 4) and (3) constructing cushion concrete, wherein the cushion layer adopts C15 plain concrete with the thickness of 100mm, and the cushion layer concrete is required to be maintained in time after the construction is finished so as not to cause shrinkage cracks in the concrete.
Detailed Description
In order to further understand the contents, features and effects of the present invention, the following embodiments are described in detail as follows:
the invention relates to a safe construction method for excavation of a foundation pit, which comprises the following steps,
(1) releasing a foundation pit excavation boundary line on the original ground according to a construction drawing, measuring the elevation and determining the excavation depth;
(2) excavating a surface layer of the foundation pit by using a backhoe excavator, and directly transporting the earthwork obtained after excavation outwards by using a self-dumping vehicle;
in this embodiment, a step of edge protection is further provided between the steps (1) and (2), and the step is performed around the foundation pit
The steel pipe is driven into the ground to 1000mm deep to be used as a vertical rod of a protective railing, the distance between the steel pipe and the side of a foundation pit is 500mm, the protective railing consists of an upper cross rod, a middle cross rod and a lower cross rod and the vertical rods, the distance between the cross rods is 0.6m, the height of the upper rod from the ground is 1.3m, the height of the lower rod from the ground is 0.1m, and the distance between the vertical rods is 2 m; and hanging a safety prompt slogan and a safety warning board at the periphery of the foundation pit. Protection railing and safety warning sign etc. are set up through the outside at the foundation ditch, promote the security of work progress.
(3) Excavating the foundation pit layer by layer in a layered excavation mode, wherein the excavation depth of each layer is 1.5-2 m;
(4) placing slopes on two sides in the excavation process of the foundation pit, wherein the slope is 60-75 degrees, and carrying out soil nailing wall type supporting on the placed slopes after each layer of excavation is finished; the method for supporting in a wall nailing mode comprises the steps of slope trimming and hole site distribution, the steps of manufacturing and placing soil nails, the step of grouting, the steps of hanging a net and installing an anchor head and the step of spraying concrete to form a protective layer;
(5) cleaning the bottom of the substrate with the residual 0.2-0.3m by manual work;
(6) performing cast-in-place pile construction on the foundation of the foundation pit; the method for constructing the cast-in-place pile comprises the steps of paying off the pile position, embedding the pile casing, drilling and picking up the slag, placing the reinforcement cage, pouring concrete and pulling out the pile casing.
(7) Constructing a concrete structure cushion layer on the base of the foundation pit; the construction method of the structural cushion comprises the steps of groove inspection of the foundation pit, retesting and measurement lofting, formwork support and elevation retest and concrete pouring of the cushion.
The above steps are explained in detail with reference to the construction process as follows:
(1) releasing a foundation pit excavation boundary line on the original ground according to a construction drawing, measuring the elevation and determining the excavation depth; and filling a lofting record table, reporting and measuring a responsible person for rechecking, and excavating the foundation pit after confirming that no errors exist.
(2) Excavating a surface layer of the foundation pit by using a backhoe excavator, and directly transporting the earthwork obtained after excavation outwards by using a self-dumping vehicle; because the surface course is in excavation earlier stage during excavation, the foundation ditch degree of depth is lighter, and the dumper can be opened to the foundation ditch along earthwork transportation ramp and be carried the loading, when the foundation ditch did not excavate to the deeper degree, the twice of transporting through the excavator after the earthwork excavation also can adopt the direct loading of dumper to carry away.
(3) Excavating the foundation pit layer by layer in a layered excavation mode, wherein the excavation depth of each layer is 1.5-2 m;
(4) placing slopes on two sides in the excavation process of the foundation pit, wherein the slope is 60-75 degrees, and carrying out soil nailing wall type supporting on the placed slopes after each layer of excavation is finished;
in particular, the amount of the solvent to be used,
1) slope finishing
The side slope surface is cleaned manually, and in order to ensure the smoothness of the sprayed concrete surface layer, the process needs to be positioned by hanging wires. For the side slope with larger soil layer water content, a horizontal drainage pipe wrapped filter screen with the length of 400-600mm and the diameter of not less than 40mm can be inserted into the back of the supporting surface layer, the outer end of the horizontal drainage pipe wrapped filter screen extends out of the supporting surface layer, and the distance is 2m, so that accumulated water after the concrete surface layer is sprayed can be drained away.
2) Hole site distribution
The position of each soil nail is discharged by a measurer according to a design drawing. The soil nailing reinforcing steel bars are arranged according to a quincunx by adopting C22 or C25, the horizontal spacing is 1.5m or 2.0m, and the vertical spacing is 1.5 m.
3) Soil nail making and placing
The soil nail adopts the pre-drilling and then installs the soil nail anchor rod, the soil nail anchor adopts A8 steel bar as the support, the pipe head is fully welded with the single side of the C22 soil nail hook by the C16 reinforcing rib and is welded on the steel bar net.
4) Grouting
After the hole is formed, the soil nail reinforcing steel bar is timely placed into the hole, P.SA32.5 cement is adopted for grouting, the water cement ratio is 0.5-0.55, and the design strength of slurry is not lower than 20 MPa. Gravity grouting is carried out until the slurry is full, but slurry supplement is carried out for 1-2 times; the pressure grouting adopts a secondary grouting method, and a grout stop plug and an exhaust hole are arranged at the drilling hole; the grouting guide pipe is inserted into the bottom of the hole firstly, grouting is carried out at low pressure, the guide pipe is withdrawn slowly at a constant speed, and a grout outlet of the guide pipe is always positioned below the surface of grout in the hole, so that the air in the hole can be enabled to escape completely. Filling the conduit with high pressure when the conduit is 0.5-1m away from the orifice, and maintaining the high pressure for 3-5 min; when the steel pipe is adopted, high-pressure grouting is used, and the steel pipe is plugged in time after being filled with the grouting, so that the pressure is slowly diffused; during grouting, an early strength agent and an expanding agent are added to improve the early strength of a grouting body and increase the friction force between the grouting body and a soil body on a hole wall.
5) Mounting of hanging net and anchor head
Reinforcing mesh (
150mm × 150mm) is fixed by steel bars inserted into the soil, the gap between the steel bars and the slope surface is 3-4cm, the steel bars are lapped and bound one by one from top to bottom and from left to right during lapping, the lapping length is more than 30cm and not less than two-point spot welding, and the steel bar net sheets are provided with horizontal fixing bars.
6) Sprayed concrete
The sprayed concrete dry material is manually stirred on site, P.S. A32.5 cement, fine sand and 5-10mm mechanically-broken stone are used, and an accelerating agent is needed in a collapse-prone area to improve the setting speed of surface concrete.
The slope is hung the net and is sprayed concrete and protect, sets up horizontal strengthening rib simultaneously, and vertical interval is 1 m. The horizontal reinforcing ribs are welded with reinforcing steel bars implanted into the side slope soil body and are firmly connected with a reinforcing steel bar mesh. The strength grade of the sprayed concrete is C20, and the thickness of the sprayed concrete is 100 mm.
(5) Cleaning the bottom of the substrate with the residual 0.2-0.3m by manual work;
(6) performing cast-in-place pile construction on the foundation of the foundation pit;
in particular, the amount of the solvent to be used,
1) preparation for construction
And (4) leveling the field, removing impurities, replacing soft soil, ramming tightly and planning the mud pit uniformly.
2) Measuring line
Measuring the pile position by using a total station according to a construction drawing and a site lead control point, and driving a timber pile; the cross method is adopted to lead the pile to the periphery and the short steel bars are used for making the pile protection.
3) Embedded protection cylinder
The protective cylinder is an integral steel protective cylinder welded by a steel plate with the plate thickness of 4-6mm, and the diameter and the burial depth of the protective cylinder are determined according to a design drawing. The excavation diameter is 0.2-0.4m larger than the pile casing, and the depth of the pit bottom is as high as the bottom of the pile casing. 2 overflow ports are arranged on the pile casing, when the pile casing is buried, the center of the pile casing is coincided with the center of the pile casing, and the deviation of the pile casing is not more than 20 mm; and the verticality deviation of the pile casing is strictly kept to be not more than 1%, and the top of the pile casing is 0.3m higher than the ground. After the position of the pile casing is correctly fixed, clay with the optimal water content is uniformly backfilled around the pile casing, and the pile casing is tamped in layers to ensure the quality of formed holes.
4) Slurry preparation
And bentonite slurry is adopted for wall protection. In the pore-forming process, a slurry system needs to be cleaned regularly to ensure civilized construction. The mud pit is managed and responsible by specially-assigned persons.
5) Drilling to form holes
And during drilling, grouting while drilling to protect the wall, keeping the mud surface not lower than 0.5m below the top of the protective cylinder, detecting the verticality at any time in the drilling process, and adjusting at any time. After the hole is formed, the specific gravity of the slurry is controlled within 1.25, and the record is made when the hole is formed.
6) Cleaning hole
Cleaning holes for the first time: after pile holes are formed, performing first hole cleaning before a reinforcement cage is inserted into the holes, removing drilling slag by using an in-hole drilling bucket (a drilling bucket with a baffle), and performing turbid water circulation by using a water pump if the precipitation time is long so that the density reaches about 1.2; cleaning the hole for the second time: and (4) after the steel reinforcement cage and the guide pipe are placed, performing secondary hole cleaning by using an air lift method, wherein the secondary hole cleaning time is not less than 30 min.
7) Manufacturing and installation of reinforcement cage
A. Processing a steel reinforcement cage:
the reinforcement cage is manufactured by field processing, and the processing size is strictly controlled according to design drawings and standard requirements. The main reinforcement of the reinforcement cage is welded, the welding method and the length meet the design requirements, and the main reinforcement and the stirrup are spot-welded. In order to facilitate hoisting, the reinforcement cage is manufactured in advance in a segmented mode, the orifices are welded on site, and the reinforcement joints are staggered according to the regulations.
In order to ensure the thickness of the protective layer of the cast-in-place pile, a method of welding steel bar ears is adopted. The ears of the reinforcing steel bars are welded on the outer side of the main reinforcing steel bars of the framework at intervals of 2-4 m. In order to ensure the rigidity of the reinforcement cage and prevent deformation during hoisting, reinforcing ribs are required to be additionally arranged every 2 m.
The finished reinforcement cage must be placed on a flat, dry ground. When the storage box is stored, square wood with the same height is laid on the contact part of each reinforcing rib and the ground so as to prevent soil from being adhered. The formed framework is marked by a tag, so that errors in hoisting are avoided.
After the reinforcement cage is processed, the reinforcement cage can be used after being qualified by reporting, supervising and checking.
B. Hoisting a steel reinforcement cage:
and hoisting the steel reinforcement cage by adopting a crawler crane. When in lifting, double lifting points are needed, and the lifting points are properly arranged at the reinforced stirrup (the lifting points are welded). The large hook and the small hook are matched with each other to hoist the reinforcement cage, and the lower part of the small hook and the upper part of the large hook are hoisted. A pulley is hung on a small hook of a crane, a steel wire rope penetrates through the pulley, two ends of the steel wire rope are firmly connected with reinforcement stirrups of a reinforcement cage by adopting a U-shaped snap ring, two steel wire ropes are symmetrically arranged on the upper portion of the reinforcement cage, two ends of the steel wire rope are firmly connected with the reinforcement stirrups of the reinforcement cage by adopting the U-shaped snap ring, one pulley is arranged on each steel wire rope, the two pulleys are hung on a carrying pole (made of profile steel), and a lifting hook is arranged on the upper portion of the carrying pole and hung on a large hook of. When the lifting device is lifted, the big hook and the small hook are stressed simultaneously, the big hook lifts the reinforcement cage upwards, the small hook plays a role in stabilizing the reinforcement cage, meanwhile, the reinforcement cage is prevented from bending deformation, the reinforcement cage is lifted and straightened slowly in a mutually matched mode, meanwhile, a specially-assigned person is arranged to support the lower portion of the reinforcement cage stably, and the reinforcement cage is guaranteed to be always in a stable state in the lifting process. After the steel reinforcement cage is hung straight, the steel reinforcement cage is aligned with the hole position and slowly lowered, the steel reinforcement cage cannot swing to collide with the hole wall or forcibly enter the hole, and the steel reinforcement cage must be kept in a vertical state when being installed into the hole.
C. Underwater concrete pouring
After cleaning and lowering the cage, C30 concrete is poured immediately. The slump of the concrete mixture discharged from the transport tank truck into the guide pipe is 18cm-22cm, the initial setting time of the first poured concrete is not earlier than the time for completing the whole concrete pouring of the cast-in-place pile, and the pouring time is shortened as much as possible for continuous operation.
Firstly, a guide pipe is arranged, a 25t crane is used for hanging the guide pipe (the diameter is not less than 250mm) into the hole, the position is kept in the middle, and the lower opening of the guide pipe and the bottom of the hole are kept about 30-50 cm. Before using the conduit and after pouring 4-6 piles, the tightness of the conduit and the joints thereof needs to be checked to ensure good sealing. Before the first batch of concrete is poured, a water-proof plug is placed in the funnel, and then the first batch of concrete is placed. After confirming that the storage capacity is sufficient, the iron wire can be cut off, and water in the conduit is removed by the weight of the concrete, so that the waterproof plug is left at the bottom of the hole. The first batch of concrete is poured in an amount that the conduit is embedded into the concrete to a depth of not less than 1.0 m. After the first batch of concrete is normally poured, the concrete is continuously poured, the height of the concrete surface is detected by using a measuring hammer in the pouring process, the depth of the lower end of the guide pipe embedded into the concrete is calculated, and the record is made so as to correctly guide the lifting and the dismantling of the guide pipe. And lifting the guide pipe until the lower end of the guide pipe is embedded into the concrete to a depth of 4m, and then continuously pouring. The slurry overflowing from the well bore should be drained to a proper place for treatment during the pouring process to prevent environmental pollution.
D. Pile detection
After the construction is finished, a qualified detection unit is entrusted to carry out a small strain test on the engineering pile and a large strain test of 5-10% of the total number of the pile foundations, and the pile forming effect of the single pile is checked.
(7) Constructing a concrete structure cushion layer on the base of the foundation pit; the construction method of the structural cushion comprises the steps of groove inspection of the foundation pit, retesting and measurement lofting, formwork support and elevation retest and concrete pouring of the cushion.
In particular, the amount of the solvent to be used,
1) foundation pit inspection groove
A. And cleaning up the floating soil on the surface of the foundation pit, wherein the elevation and the surface flatness meet the design requirements and the specification. And (4) carrying out sectional inspection according to the program, carrying out foundation treatment on the found soil layer which does not meet the design requirement according to the suggestion of the design unit, and after the treatment is finished, asking the supervision unit to accept and transact the hidden inspection record.
B. And checking whether the position, the number and the plane size of the sump tank conform to the design or not by contrasting a drawing.
C. As the engineering foundation pit has multiple supporting modes, the grooves are tested in sequence according to the working surfaces provided by side slope supporting and earthwork excavation so as to save the construction period.
2) Retesting and measurement lofting
And after the foundation pit is excavated, retesting the size and the position deviation of the excavation of the foundation pit, wherein the size and the position deviation of the excavation of the foundation pit must meet the requirements of construction and specification. The boundary line and elevation of the cushion layer can be measured and lofted according to the construction drawing.
3) Formwork supporting and elevation rechecking
The engineering cushion layer template adopts wood beams as side molds and keeps the stability of the side molds. And (4) retesting the elevation by using the level gauge to prevent the elevation from being wrong after the cushion layer is poured.
4) Concrete pouring of bedding
A. The cushion layer adopts C15 plain concrete, and the thickness is 100 mm.
B. The concrete at the construction stage of the cushion layer adopts a fixed concrete delivery pump, and delivery pump pipes are erected according to the pouring sequence when the cushion layer is poured.
C. And (3) operating according to a section of 30m, setting a contraction joint, pumping concrete by using a conveying pump, manually paving, and tamping by using a flat plate vibrator.
D. And after the cushion concrete is constructed, the smooth, clean and dry surface of the cushion concrete is ensured, and then the waterproof mortar leveling layer is constructed on the surface of the cushion concrete according to the design requirement. And paying off and dividing construction according to the width of 3.0m when the mortar is coated, and carrying out 'slurry lifting, compacting and finishing' processes before final setting of the mortar so as to ensure that the surface of the waterproof mortar is smooth and flat.
E. Digging a drainage ditch and a water collecting pit in the pit, and draining accumulated water on the substrate; and when the water seepage at the pit bottom is large and certain confined water exists, pouring cushion concrete after taking measures of drainage and pressure reduction.
F. After the concrete of the cushion layer is constructed, attention needs to be paid to timely maintenance so as to prevent the concrete from generating shrinkage cracks.
Other auxiliary security measures are:
1) when the foundation pit is excavated, the operation distance between two manual bottom clearing persons is larger than 3.0m, and the two manual bottom clearing persons cannot dig in opposite directions; when the excavation area is large, the work of each person is not 6 square meters. The soil excavation is carried out sequentially from top to bottom and in a layered and sectional manner, and the slope toe excavation or the soil excavation on the contrary is strictly forbidden, or the soil excavation method of bottom excavation and soil collapse is adopted.
2) The foundation pit excavation should be strictly put on the slope according to the regulations, the change condition of the soil wall should be noticed at any time during the excavation, if cracks or partial collapse phenomena are found, the supporting or the slope putting should be carried out in time, and the stability of the supporting and the change of the soil wall should be noticed. When excavation without slope release is adopted, temporary supports are required to be arranged.
3) The deep foundation pit should be excavated, supported and inclined first, and take precautions to forbid trampling and supporting.
4) When the earthwork is lifted manually, whether the lifting tool and the rope are firm or not should be checked. People cannot stand under the bucket, and the soil heap should leave the pit edge for a certain distance to prevent the pit wall from collapsing.
5) When the handcart is used for carrying soil, a road is firstly leveled, and a one-way road is adopted as much as possible so as to avoid back-and-forth collision; when the flat car and the dump truck are used for carrying soil, the distance between the two cars is not less than 10m, and when the soil is loaded and unloaded, the distance between the two cars is not less than 1 m.
6) The vertical walls and the side slopes of the foundation pit and the pipe trench are prevented from collapsing during the excavation process and the open period and protected if necessary; the soil around the column base must not be piled too high.
7) The safe distance between the heavy object and the soil slope; the distance between the crawler excavator and the digging edge is not less than 0.8m, the distance between the automobile and the digging edge is not less than 3m, and the distance between the crane and the digging edge is not less than 4 m; the height of the mound is not more than 1.5 m.
8) When the foundation pit is deep or the airing time is long, the water loss of the side slope is prevented, or the side slope is prevented from being loose or the ground is prevented from being washed and infiltrated by water. The slope stability is affected, and a slope protection method is adopted.
9) After the large excavation foundation pit is formed, a protective frame and a drainage ditch are arranged around the edge of the foundation pit.
Claims (5)
1. A safe construction method for foundation pit excavation is characterized by comprising the following steps: comprises the following steps of (a) carrying out,
(1) releasing a foundation pit excavation boundary line on the original ground according to a construction drawing, measuring the elevation and determining the excavation depth;
(2) excavating a surface layer of the foundation pit by using a backhoe excavator, and directly transporting the earthwork obtained after excavation outwards by using a self-dumping vehicle;
(3) excavating the foundation pit layer by layer in a layered excavation mode, wherein the excavation depth of each layer is 1.5-2 m;
(4) placing slopes on two sides in the excavation process of the foundation pit, wherein the slope is 60-75 degrees, and carrying out soil nailing wall type supporting on the placed slopes after each layer of excavation is finished;
(5) cleaning the bottom of the substrate with the residual 0.2-0.3m by manual work;
(6) performing cast-in-place pile construction on the foundation of the foundation pit;
(7) and constructing a concrete structure cushion layer on the foundation of the foundation pit.
2. The method of claim 1, wherein the method comprises: a step of edge protection is also arranged between the steps (1) and (2), and the step is used around the foundation pit
The steel pipe is driven into the ground to 1000mm deep to be used as a vertical rod of a protective railing, the distance between the steel pipe and the side of a foundation pit is 500mm, the protective railing consists of an upper cross rod, a middle cross rod and a lower cross rod and the vertical rods, the distance between the cross rods is 0.6m, the height of the upper rod from the ground is 1.3m, the height of the lower rod from the ground is 0.1m, and the distance between the vertical rods is 2 m; and hanging a safety prompt slogan and a safety warning board at the periphery of the foundation pit.
3. The method of claim 2, wherein the method comprises: the step of soil nailing wall support in the step (4) is that,
1) trimming a side slope, manually cleaning the side slope to ensure the smoothness of a sprayed concrete surface layer, and performing line hanging and positioning in the process; for the side slope with large water content of the soil layer, a horizontal drainage pipe with the length of 400-600mm and the diameter of not less than 40mm is inserted into the back of the supporting surface layer to wrap the filter screen, the outer end of the horizontal drainage pipe extends out of the supporting surface layer at the interval of 2m, and accumulated water after the concrete surface layer is sprayed is drained away;
2) arranging the holes, namely, arranging the positions of each soil nail by a measurer according to a design drawing, wherein the soil nail steel bars are arranged according to a quincunx by adopting C22 or C25, the horizontal distance is 1.5m or 2.0m, and the vertical distance is 1.5 m;
3) manufacturing and placing soil nails, mounting a soil nail anchor rod after pre-drilling holes on the soil nails, wherein the soil nail anchor rod adopts A8 steel bars as a bracket, and a pipe head is fully welded with one side of a C22 soil nail hook by using a C16 reinforcing rib and is welded on a steel bar net;
4) grouting, namely placing the soil nail steel bars into the holes after hole forming, wherein the grouting adopts P.SA32.5 cement, the water cement ratio is 0.5-0.55, and the strength of slurry is not lower than 20 MPa; during grouting, an early strength agent and an expanding agent are added to improve the early strength of a grouting body and increase the friction force between the grouting body and a soil body on a hole wall;
5) hanging net and anchor head installation, reinforcing bar net piece
150mm × 150mm) is fixed by steel bars inserted into the soil, the gap between the steel bars and the slope surface is 3-4cm, the steel bars are lapped and bound one by one from top to bottom and from left to right during lapping, the lapping length is more than 30cm and is not less than two pointsWelding, wherein a reinforcing steel bar net sheet is provided with a horizontal fixing rib;
6) spraying concrete, manually stirring the sprayed concrete dry materials on site, adding a quick-setting admixture in a collapse-prone area by using P.S. A32.5 cement, fine sand and 5-10mm mechanically-broken stones to improve the setting speed of surface concrete; side slope net hanging and concrete spraying are carried out for protection, meanwhile, horizontal reinforcing ribs are arranged, and the vertical distance is 1 m; the horizontal reinforcing ribs are welded with reinforcing steel bars implanted into the slope soil body and are firmly connected with a reinforcing steel bar mesh; the strength grade of the sprayed concrete is C20, and the thickness of the sprayed concrete is 100 mm.
4. The method of claim 3, wherein the method comprises: the construction of the cast-in-place pile in the step (6) comprises the following steps,
1) construction preparation, flattening a field, removing impurities, replacing soft soil, ramming tightly and planning a mud pit uniformly;
2) measuring and paying off, namely determining the pile position by using a total station according to a construction drawing and a field lead control point, and driving a timber pile; leading the pile to the periphery by a cross method and using short steel bars to make a pile protector;
3) embedding a pile casing, wherein the pile casing is an integral steel pile casing welded by a steel plate with the plate thickness of 4-6mm, and the diameter and the burial depth of the pile casing are determined according to a design drawing; the excavation diameter is 0.2-0.4m larger than the pile casing, and the depth of the pit bottom is as high as the bottom of the pile casing; 2 overflow ports are arranged on the pile casing, when the pile casing is buried, the center of the pile casing is superposed with the center of the pile, the deviation is less than or equal to 20mm, the deviation of the verticality of the pile casing is kept to be less than or equal to 1%, and the top of the pile casing is 0.3m higher than the ground;
4) preparing slurry;
5) drilling to form a hole, wherein during drilling, mud is injected while drilling to protect the wall, the mud surface is always not lower than 0.5m below the top of the protective cylinder, the verticality is detected at any time during drilling, and the mud specific gravity is controlled within 1.25 after hole forming;
6) cleaning holes, cleaning holes for the first time: after pile holes are formed, performing first hole cleaning before the reinforcement cage is inserted into the holes, removing drilling slag by using an in-hole drilling bucket, and if the settling time is long, performing turbid water circulation by using a water pump to enable the density to reach about 1.2; cleaning the hole for the second time: after the steel reinforcement cage and the guide pipe are placed, secondary hole cleaning is carried out by an air lift method, and the time for secondary hole cleaning is not less than 30 min;
7) manufacturing and installing a reinforcement cage, namely manufacturing the reinforcement cage and placing the reinforcement cage into the pile hole;
8) underwater concrete pouring, and pouring concrete into the pile hole;
9) and (3) pile detection, after the construction is finished, carrying out a small strain test and a large strain test of 5-10% of the total number of pile foundations on the engineering pile, and checking the pile forming effect of the single pile.
5. The method of claim 4, wherein the method comprises: the concrete structure cushion layer construction in the step (7) comprises the following steps,
1) the method comprises the following steps of (1) checking a groove of a foundation pit, cleaning up floating soil on the surface of the foundation pit, enabling elevation and surface flatness to meet design requirements and standard regulations, carrying out sectional groove checking according to a program, carrying out foundation treatment on a found soil layer which does not meet the design requirements according to the opinions of a design unit, and after the treatment is finished, asking a supervision unit to accept the foundation treatment and handling hidden inspection records;
2) retesting and measuring lofting, retesting the size and the position deviation of the foundation pit excavation after the foundation pit excavation is finished, wherein the size and the position deviation of the foundation pit excavation should meet the construction and specification requirements;
3) the method comprises the following steps of (1) formwork erecting and elevation retest, wherein a wood beam is used as a side formwork of the engineering cushion formwork and is kept stable, and a level gauge is used for retesting the elevation so as to prevent elevation errors after the cushion is poured;
4) and (3) constructing cushion concrete, wherein the cushion layer adopts C15 plain concrete with the thickness of 100mm, and the cushion layer concrete is required to be maintained in time after the construction is finished so as not to cause shrinkage cracks in the concrete.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010276763.4A CN111456019A (en) | 2020-04-10 | 2020-04-10 | Safe construction method for foundation pit excavation |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010276763.4A CN111456019A (en) | 2020-04-10 | 2020-04-10 | Safe construction method for foundation pit excavation |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN111456019A true CN111456019A (en) | 2020-07-28 |
Family
ID=71676764
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202010276763.4A Withdrawn CN111456019A (en) | 2020-04-10 | 2020-04-10 | Safe construction method for foundation pit excavation |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN111456019A (en) |
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112160324A (en) * | 2020-08-25 | 2021-01-01 | 南通大学 | Construction method for deep foundation pit support |
| CN113356221A (en) * | 2021-06-30 | 2021-09-07 | 中国葛洲坝集团生态环境工程有限公司 | Polluted foundation pit supporting and rapid excavation construction method |
| CN113482005A (en) * | 2021-07-26 | 2021-10-08 | 宏腾建设集团有限公司 | Small foundation pit earthwork excavation method |
| CN113914327A (en) * | 2021-11-08 | 2022-01-11 | 浙江乔兴建设集团有限公司 | Construction method for foundation pit enclosure and earth excavation |
| CN114075805A (en) * | 2020-11-18 | 2022-02-22 | 上海园林（集团）有限公司 | Construction method for foundation earthwork of trestle |
| CN114232566A (en) * | 2021-12-09 | 2022-03-25 | 中铁十局集团第三建设有限公司 | Construction method for excavating complicated geological ultra-wide ultra-deep section river channel |
| CN115419074A (en) * | 2022-09-28 | 2022-12-02 | 中建八局第三建设有限公司 | Crawler-type earth-conveying and excavating method for ultra-deep foundation pit |
| CN116876417A (en) * | 2023-07-06 | 2023-10-13 | 广东省水利水电第三工程局有限公司 | Bank protection construction process |
-
2020
- 2020-04-10 CN CN202010276763.4A patent/CN111456019A/en not_active Withdrawn
Cited By (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112160324A (en) * | 2020-08-25 | 2021-01-01 | 南通大学 | Construction method for deep foundation pit support |
| CN114075805A (en) * | 2020-11-18 | 2022-02-22 | 上海园林（集团）有限公司 | Construction method for foundation earthwork of trestle |
| CN113356221A (en) * | 2021-06-30 | 2021-09-07 | 中国葛洲坝集团生态环境工程有限公司 | Polluted foundation pit supporting and rapid excavation construction method |
| CN113482005A (en) * | 2021-07-26 | 2021-10-08 | 宏腾建设集团有限公司 | Small foundation pit earthwork excavation method |
| CN113482005B (en) * | 2021-07-26 | 2022-08-09 | 宏腾建设集团有限公司 | Small foundation pit earthwork excavation method |
| CN113914327A (en) * | 2021-11-08 | 2022-01-11 | 浙江乔兴建设集团有限公司 | Construction method for foundation pit enclosure and earth excavation |
| CN114232566A (en) * | 2021-12-09 | 2022-03-25 | 中铁十局集团第三建设有限公司 | Construction method for excavating complicated geological ultra-wide ultra-deep section river channel |
| CN115419074A (en) * | 2022-09-28 | 2022-12-02 | 中建八局第三建设有限公司 | Crawler-type earth-conveying and excavating method for ultra-deep foundation pit |
| CN115419074B (en) * | 2022-09-28 | 2023-09-08 | 中建八局第三建设有限公司 | Crawler-type soil conveying and excavating method for ultra-deep foundation pit |
| CN116876417A (en) * | 2023-07-06 | 2023-10-13 | 广东省水利水电第三工程局有限公司 | Bank protection construction process |
| CN116876417B (en) * | 2023-07-06 | 2024-02-27 | 广东省水利水电第三工程局有限公司 | Bank protection construction process |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN111456019A (en) | Safe construction method for foundation pit excavation | |
| CN111733828A (en) | Large-section deep foundation pit fender pile and prestressed anchor cable supporting construction technology | |
| CN108894214B (en) | Karst cave geological environment cast-in-place pile and pile-forming construction method thereof | |
| CN111576431A (en) | Excavation method for foundation pit of four-layer subway station | |
| CN109778869A (en) | Foundation ditch construction method | |
| CN113174961B (en) | Foundation pit slope supporting method | |
| CN112376589A (en) | Landslide belt pile plate type comprehensive protection construction system and construction method | |
| CN112281857A (en) | Deep foundation pit excavation construction method | |
| CN108301440A (en) | With waterproof, the underground pipe gallery construction method of drain function | |
| CN113914327A (en) | Construction method for foundation pit enclosure and earth excavation | |
| CN113174958A (en) | Construction method for foundation pit of adjacent road under poor ground condition | |
| CN112482358A (en) | Diaphragm wall construction method for diaphragm wall penetrating stratum | |
| CN211144503U (en) | High steep topography bridge tunnel meets section open cut tunnel and connects long structure | |
| CN114837088A (en) | Construction method of bearing platform on highway | |
| CN112012197A (en) | Manual hole digging pile and construction method thereof | |
| CN216194901U (en) | Unloading plate type retaining wall structure for large-span underground garage | |
| CN109024657B (en) | Construction method of super high-rise core tube deep pit edge tower crane foundation under complex conditions | |
| CN110924401A (en) | Construction foundation pit supporting mode for combined arching and bearing of mixing piles and cast-in-place piles | |
| CN109403316A (en) | A kind of manually digging hole combines the pile base construction method of realization with mechanical hole building | |
| CN111456143A (en) | Open excavation construction equipment for comprehensive pipe gallery and construction method thereof | |
| CN113550764A (en) | Method for starting shield concrete sleeve to enter hole and building structure | |
| CN114991165A (en) | Construction method for subway deep foundation pit adjacent to railway business line | |
| CN114855789A (en) | Construction method for broken pile treatment of engineering pile in soft soil area | |
| CN112095377B (en) | Off-pit construction road structure next to subway deep foundation pit and construction method thereof | |
| CN115045262B (en) | Karst landform Gao Tianfu foundation pile foundation construction method |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| WW01 | Invention patent application withdrawn after publication |
Application publication date: 20200728 |
|
| WW01 | Invention patent application withdrawn after publication |