A method for constructing deep foundation pits

Abstract

This invention relates to the field of foundation pit construction technology and discloses a method for deep foundation pit construction, comprising the following steps: S1, surveying and setting out: placing marker points at the corners of the area to be excavated for the deep foundation pit, and drawing the excavation route on the ground along the marker points; S2, excavating a closed-loop channel for the foundation pit along the set route: excavating a closed-loop channel below the excavation route according to the project requirements and indicators, and placing baffles higher than the ground on both sides of the channel to prevent external water flow from entering the middle area; S3, drilling holes and grouting at the set-out points using a drilling rig. This invention connects the cast-in-place piles, the cement columns in the grouting holes at the set-out points, and the cement columns in the grouting holes at a distance by drilling holes tangentially to the channel. This significantly improves the compressive strength of the inner walls of the deep foundation pit, and this foundation pit excavation method is also more suitable for the excavation and construction of deeper foundation pits.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of foundation pit construction, in particular to a deep foundation pit construction method. BACKGROUND

[0002] A foundation pit is a soil pit excavated at the foundation design position according to the foundation elevation and the foundation plane size. Before excavation, the excavation scheme should be determined according to the geological and hydrological data, combined with the situation of the buildings near the site, and the waterproof and drainage work should be done well. For those not deep, the method of slope can be used to make the soil slope stable, and the slope size is determined according to the relevant construction regulations. For those deep and adjacent to buildings, the method of foundation pit wall support can be used, and the method of spraying concrete retaining wall can be used for large foundation pits, and even the method of underground continuous wall and column type bored pile chain can be used to prevent the collapse of the soil layer outside.

[0003] The traditional deep foundation pit construction method mainly includes the following shortcomings:

[0004] (1) The compressive resistance of the deep foundation pit is relatively poor. The traditional deep foundation pit construction method often only uses anchor rods to divide the pressure of the foundation pit retaining wall when excavating relatively deep foundation pits. However, as the depth of the foundation pit increases, the soil quality will change, and at this time, only the length of the anchor rod can be increased to cope with the consequences of soil quality changes, and increasing the anchor rod will greatly increase the difficulty of construction.

[0005] (2) The pressure on one side of the foundation pit cannot be dispersed. The traditional deep foundation pit construction method cannot share the pressure on one side with the retaining walls on the other three sides when encountering large pressure on one side, which greatly reduces the compressive resistance of the foundation pit

[0006] In view of the above, a deep foundation pit construction method needs to be designed. SUMMARY

[0007] (I) Technical problems to be solved

[0008] In view of the deficiencies of the prior art, the present application provides a deep foundation pit construction method to solve the problems raised in the background art.

[0009] (II) Technical scheme

[0010] To achieve the above purpose, the present application provides the following technical scheme: a deep foundation pit construction method, comprising the following steps:

[0011] S1, measurement and line laying: placing mark points at the corners of the area where the deep foundation pit needs to be excavated, and drawing the route to be excavated on the ground along the mark points;

[0012] S2, excavate a closed loop channel along the placed route: according to the requirements and indicators of the project, a closed loop channel is excavated under the digging route, and a higher than ground baffle is placed on both sides of the channel, which can prevent external water flow from entering the middle area;

[0013] S3, drill and grout at the line: multiple grouting holes are continuously excavated directly below the digging route and in the middle area of the channel, and each grouting hole is cleaned and then a corresponding size and type of steel reinforcement cage is placed. Finally, multiple grouting holes can be grouted at the same time or within a short period of time, and after the grouting holes are filled with grout, the channel inside also needs to be grouted, and clear water is injected into the grout in the channel at intervals to ensure that the grout can delay the setting time, so that the grout can better penetrate to the deep part of the grouting hole;

[0014] S4, drill and grout along the tangential direction of the channel and at a certain distance outward: after uniformly punching and cleaning around the channel, mud is injected after the same proportion of steel reinforcement cage is placed, and after the mud is solidified, the grouting hole is paved with soil and compacted above;

[0015] S5, excavation and grouting of mud wall bored pile: the position of the mud wall bored pile should be aligned with the far grouting hole and the middle grouting hole, and the height of the bored pile should be lower than the ground height by a certain distance;

[0016] S6, drill in the tangential direction of the channel and install anchor rods to connect the bored pile, the grouting hole at the line and the far grouting hole: the anchor rod can be divided into a main anchor rod and a secondary anchor rod. The main anchor rod connects the bored pile, the cement column in the grouting hole at the line and the cement column in the far grouting hole, and the secondary anchor rod is placed inside the bored pile according to the stress condition. The secondary anchor rod connects the bored pile and the cement column in the grouting hole at the line;

[0017] S7, tie the exposed anchor rod with the reserved steel reinforcement of the grouting pile and pour mud after welding: since the height of the bored pile is lower than the ground, the mud guard is used at this time. After tying the steel reinforcement at the end of the first layer of anchor rod with the reserved steel reinforcement, mud is laid to make the height of the laid mud equal to the construction height in the channel;

[0018] S8, excavation and dewatering of earthwork: the earthwork is excavated and dewatered layer by layer, and a hole is punched on the surface of the bored pile and an anchor rod is placed after each layer of earthwork is excavated.

[0019] Preferably, in step S3, a multi-axis puncher can be used for punching the grouting hole, which can ensure punching efficiency and is not prone to position deviation.

[0020] Preferably, in step S4, when drilling grouting holes along the tangential direction of the channel, the distance between the grouting holes and the channel should not be too large.

[0021] Preferably, in step S7, a steel bar is reserved at the top of the cast-in-place pile and connected to the steel bar laid on the top layer. When the soil is excavated layer by layer and anchor rods are installed, the anchor rods can be directly connected to the inner surface of the cast-in-place pile using bolts.

[0022] Preferably, step S5 includes the following specific steps:

[0023] S501. Clean the dust and dirt inside the hole after drilling: After drilling, it is also necessary to clean the dust and dirt inside the hole to improve the adhesion of the injected mud.

[0024] S502. Place a steel cage into the hole, and the height of the cage should be higher than the ground: The height of the reserved steel cage should not be higher than the ground, so that it can be easily welded to the top anchor rod and will not affect the laying of mud on the inside of the channel.

[0025] S503. A sealing cylinder of a certain height is placed on top of the steel cage;

[0026] S504. Inject mud into the cylinder above the hole, and the mud level should be higher than the ground level.

[0027] S505. Add an appropriate amount of water to allow it to penetrate deep into the hole: Adding an appropriate amount of water can delay the hardening of the cement, so that the slurry can penetrate deeper into the grouting hole.

[0028] S506. Bend the steel bars that extend above the ground: the bent steel bars can be easily welded to the top anchor rod, and the steel bars can provide better support after the mud is laid on top of the cast-in-place pile.

[0029] Preferably, in step S502, the reserved height of the reinforcing bar should not be higher than the ground height, which means that after the height of the reinforcing bar exceeds the ground height, the reinforcing bar can be bent to ensure that the overall height of the reinforcing bar is not higher than the ground.

[0030] (III) Beneficial Effects

[0031] This invention provides a method for constructing deep foundation pits, which has the following beneficial effects:

[0032] (1) The present invention connects the cast-in-place piles, the cement column in the grouting hole at the laying point and the cement column in the grouting hole at a distance by drilling holes in the tangential direction of the channel and installing anchor rods. This can greatly improve the compressive strength of the inner wall of the deep foundation pit, and this foundation pit excavation construction method is also more suitable for some deeper foundation pit excavation and construction.

[0033] (2) The present invention completes grouting in multiple grouting holes and grouting in channels in a short time, and adds clean water to the channels at intervals to delay the solidification of cement. This can also utilize the water pressure in the channels to allow cement to penetrate deep into the grouting holes, which can greatly improve the adhesion of the foundation pit protection plate.

[0034] (3) In this invention, after the top anchor rod is tied and welded to the steel bar reserved in the grouting pile, mud is poured again to cover the grouting pile. In this way, the inner grouting pile and the middle grouting hole are fixed in a U-shape. At this time, when one side of the foundation pit encounters a large pressure, its pressure can be shared by the other three sides. This design can ensure that the foundation pit will not collapse. Attached Figure Description

[0035] Fig. 1 This is a flowchart of the present invention;

[0036] Fig. 2 This is a schematic diagram of the present invention;

[0037] Fig. 3 This is a detailed flowchart of step 5 of the present invention. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] like Figs. 1-3 As shown, the present invention provides a technical solution: a deep foundation pit construction method, comprising the following steps:

[0040] S1. Surveying and setting out: Place markers at the corners of the area where the deep foundation pit needs to be excavated, and draw the excavation route on the ground along the markers;

[0041] S2. Excavate a closed-loop channel along the established route: excavate a closed-loop channel below the excavation route according to the project requirements and specifications, and place baffles on both sides of the channel that are higher than the ground level. This channel can prevent external water from entering the middle area.

[0042] S3. Use a drilling rig to drill holes and grout at the laying point: Dig multiple grouting holes continuously below the excavation route and in the middle area of ​​the channel. After cleaning the ash from each grouting hole, insert steel bars of the appropriate size and type. Finally, grouting can be performed on multiple grouting holes simultaneously or completed in a short time. After filling the grouting holes with mud, grouting should also be performed inside the channel. Water should be injected into the mud in the channel at intervals to ensure that the mud can delay the solidification time, so that the mud can better penetrate into the depth of the grouting holes.

[0043] S4. Drill holes and inject grout along the tangent of the channel at a certain distance outward: After drilling holes and cleaning the ash evenly around the channel, inject grout after placing a steel cage of equal proportion. After the grout solidifies, lay soil on top of the grouting hole and compact it.

[0044] S5. Excavation and grouting of mud wall cast-in-place piles: The position of the mud wall cast-in-place piles should be aligned with the grouting holes at the far end and in the middle, and the height of the cast-in-place piles should be a certain distance below the ground level.

[0045] S6. Drill holes along the channel tangent and install anchor bolts to connect the cast-in-place piles, the grouting holes at the layout point, and the grouting holes at a distance: Anchor bolts can be divided into main anchor bolts and secondary anchor bolts. The main anchor bolts connect the cement columns in the cast-in-place piles, the grouting holes at the layout point, and the grouting holes at a distance. The secondary anchor bolts are drilled and placed inside the cast-in-place piles according to the stress conditions. The secondary anchor bolts connect the cement columns in the cast-in-place piles and the grouting holes at the layout point. By using anchor bolts to connect the cement columns in the cast-in-place piles, the grouting holes at the layout point, and the grouting holes at a distance, the compressive strength of the inner wall of the deep foundation pit can be greatly improved. This foundation pit excavation construction method is also more suitable for some deeper foundation pit excavation and construction.

[0046] S7. After welding the exposed anchor rods and the reserved steel bars of the grouting piles, pour mud: Since the height of the grouting piles is lower than the ground, mudguards are required at this time. After the steel bars at the ends of the first layer of anchor rods are tied to the reserved steel bars, mud is laid so that the height of the laid mud is the same as the height of the structure in the channel.

[0047] S8. Excavation and dewatering of earthwork: Earthwork is excavated and dewatered layer by layer, and after each layer of earthwork is excavated, holes need to be drilled on the surface of the cast-in-place piles and anchor rods need to be placed.

[0048] In step S3, a multi-axis drilling machine can be used to drill the grouting holes. This ensures drilling efficiency and prevents positional deviation. Since grouting in multiple grouting holes and channels is completed in a short time, and clean water is added to the channels at intervals to delay cement solidification, the water pressure in the channels can also be used to allow the cement to penetrate deep into the grouting holes, thereby improving the adhesion of the foundation pit lining.

[0049] In step S4, when drilling grouting holes along the tangential direction of the channel, the distance between the grouting holes and the channel should not be too large.

[0050] In step S7, a steel bar is pre-reserved at the top of the cast-in-place pile and connected to the steel bar laid on the top layer. When excavating the soil layer by layer and installing anchor rods, the anchor rods only need to be directly connected to the inner surface of the cast-in-place pile with bolts. When installing the anchor rods, the top anchor rod is connected to the pre-reserved steel bar of the cast-in-place pile and welded. Then, mud is poured again to cover the cast-in-place pile. In this way, the inner layer of cast-in-place piles and the middle layer of grouting holes are fixed in a U-shape. At this time, when one side of the foundation pit encounters greater pressure, its pressure can be distributed by the other three sides. This design can ensure that the foundation pit will not collapse.

[0051] Step S5 includes the following specific steps:

[0052] S501. Clean the dust and dirt inside the hole after drilling: After drilling, it is also necessary to clean the dust and dirt inside the hole to improve the adhesion of the injected mud.

[0053] S502. Place a steel cage into the hole, and the height of the cage should be higher than the ground: The height of the reserved steel cage should not be higher than the ground, so that it can be easily welded to the top anchor rod and will not affect the laying of mud on the inside of the channel.

[0054] S503. Place a sealing cylinder of a certain height above the reinforcing cage: The sealing cylinder is directly inserted around the hole of the cast-in-place pile. The diameter of the sealing cylinder should be larger than the diameter of the hole of the cast-in-place pile. This can ensure that the overflowing mud is still inside the sealing cylinder.

[0055] S504. Inject mud into the cylinder above the hole, and the mud level should be higher than the ground level: The purpose of the mud being higher than the ground level is to ensure that the mud is pressed down under the action of gravity, thereby compacting the cement deep in the cast-in-place pile and avoiding the presence of air bubbles that would affect the strength of the cast-in-place pile.

[0056] S505. Add an appropriate amount of water to allow it to penetrate deep into the hole: Adding an appropriate amount of water can delay the hardening of the cement, so that the slurry can penetrate deeper into the grouting hole.

[0057] S506. Bend the steel bars that extend above the ground: the bent steel bars can be easily welded to the top anchor rod, and the steel bars can provide better support after the mud is laid on top of the cast-in-place pile.

[0058] In step S502, the reserved rebar height should not be higher than the ground height. This means that after the rebar height exceeds the ground height, the rebar can be bent to ensure that the overall height of the rebar is not higher than the ground. The bent rebar needs to be covered with mud in the end to ensure the aesthetics of the construction structure.

[0059] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0060] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method of deep foundation construction, characterized by, The method comprises the following steps: S1, measuring the line: placing mark points at the corners of the area where deep foundation pits need to be excavated, and drawing the route to be excavated on the ground along the mark points; S2, excavating a closed-loop channel along the route: excavating a closed-loop channel under the excavation route according to the requirements and indexes of the project, and placing a baffle higher than the ground on both sides of the channel, which can prevent external water flow from entering the middle area; S3, drilling and grouting at the line: continuously excavating multiple grouting holes in the middle area of the channel directly below the excavation route, and sequentially cleaning the grouting holes and placing corresponding size and type of reinforcement cages, and then simultaneously or within a short time, grouting the multiple grouting holes, and after filling the grouting holes with grout, grouting the inside of the channel, and injecting clean water into the grout in the channel at intervals to ensure that the grout can delay the setting time, so that the grout can better penetrate into the deep grouting holes; S4, drilling and grouting along the tangential direction of the channel and at a certain distance outward: uniformly punching and cleaning dust around the channel, and then placing the same proportion of reinforcement cages and injecting grout, and laying soil compaction above the grouting holes after the grout is set; S5, excavation and grouting of the grout wall bored pile: the position of the grout wall bored pile should be aligned with the distant grouting hole and the middle grouting hole, and the height of the bored pile should be lower than the ground height by a certain distance; S6, reverse drilling along the tangential direction of the channel and anchoring to connect the bored pile, the grouting hole at the line and the distant grouting hole: the anchor rod is divided into a main anchor rod and a secondary anchor rod, the main anchor rod is connected with the cement column in the bored pile, the grouting hole at the line and the distant grouting hole, and the secondary anchor rod is punched and placed in the bored pile according to the stress condition, and the secondary anchor rod is connected with the cement column in the bored pile and the grouting hole at the line; S7, knotting the exposed anchor rod with the reserved reinforcement of the grouting pile and pouring grout after welding: since the height of the bored pile is lower than the ground, the baffle is used at this time, the first layer of anchor rod end steel is knotted with the reserved steel after the first layer of anchor rod end steel is knotted with the reserved steel, and then the grout is laid, so that the height of the laid grout is the same as the building height in the channel; S8, excavation and dewatering of earthwork: the earthwork is excavated and dewatered layer by layer, and a hole is punched on the surface of the bored pile and an anchor rod is placed after each layer of earthwork is excavated.

2. The method of claim 1, wherein: In the step S3, the excavation of the grouting hole is performed by a multi-axis puncher, which can ensure the punching efficiency and prevent position deviation.

3. The method of claim 1, wherein: In the step S4, when the grouting hole is punched along the tangential direction of the channel, the distance of the grouting hole should not be too far from the channel.

4. The method of claim 1, wherein: In the step S7, the top of the bored pile is reserved with steel and knotted with the steel laid on the top layer, and when the anchor rod is installed while the earthwork is excavated layer by layer, the anchor rod only needs to be connected with the inner surface of the bored pile by using bolts.

5. The method of claim 1, wherein: The step S5 comprises the following steps: S501, cleaning the dust and soil in the hole after punching: the dust and soil in the hole need to be cleaned after punching, which can improve the adhesion of the injected grout; S502, placing a reinforcement cage into the hole, the cage height being higher than the ground: the height of the reserved reinforcement cage should not be higher than the height of the ground, so as to facilitate welding with the top anchor rod and not to affect the laying of the mud inside the channel; S503, sleeving a sealing cylinder of a certain height above the reinforcement cage; S504, injecting mud into the cylinder above the hole and the mud height being higher than the ground; S505, adding appropriate amount of water to penetrate into the deep hole: adding appropriate amount of water can delay the solidification of cement, so that the mud can better penetrate into the deep hole; S506, bending the reinforcement part higher than the ground: the bent reinforcement can facilitate welding with the top anchor rod, and the reinforcement can provide better support after laying mud above the cast-in-place pile.

6. The method of claim 5, wherein: In the step S502, the height of the reserved reinforcement should not be higher than the height of the ground, which means that after the height of the reinforcement exceeds the height of the ground, the reinforcement is bent to ensure that the overall height of the reinforcement is not higher than the ground.

Images