CN111705786A - Method for vertical combination construction of composite stratum underground continuous wall and cast-in-situ bored pile - Google Patents

Method for vertical combination construction of composite stratum underground continuous wall and cast-in-situ bored pile Download PDF

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Publication number
CN111705786A
CN111705786A CN202010723971.4A CN202010723971A CN111705786A CN 111705786 A CN111705786 A CN 111705786A CN 202010723971 A CN202010723971 A CN 202010723971A CN 111705786 A CN111705786 A CN 111705786A
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China
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wall
pile
underground continuous
construction
guide
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Inventor
李光强
孙小猛
余秀平
岑峰
李勇海
宋文超
谭满生
李岩
左言言
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China Tiesiju Civil Engineering Group Co Ltd CTCE Group
Second Engineering Co Ltd of CTCE Group
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China Tiesiju Civil Engineering Group Co Ltd CTCE Group
Second Engineering Co Ltd of CTCE Group
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Application filed by China Tiesiju Civil Engineering Group Co Ltd CTCE Group, Second Engineering Co Ltd of CTCE Group filed Critical China Tiesiju Civil Engineering Group Co Ltd CTCE Group
Publication of CN111705786A publication Critical patent/CN111705786A/en
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    • EFIXED CONSTRUCTIONS
    • E02HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02DFOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D5/00Bulkheads, piles, or other structural elements specially adapted to foundation engineering
    • E02D5/18Bulkheads or similar walls made solely of concrete in situ
    • EFIXED CONSTRUCTIONS
    • E02HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02DFOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D1/00Investigation of foundation soil in situ
    • E02D1/02Investigation of foundation soil in situ before construction work
    • E02D1/022Investigation of foundation soil in situ before construction work by investigating mechanical properties of the soil
    • E02D1/025Investigation of foundation soil in situ before construction work by investigating mechanical properties of the soil combined with sampling
    • EFIXED CONSTRUCTIONS
    • E02HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02DFOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D2250/00Production methods
    • E02D2250/0023Cast, i.e. in situ or in a mold or other formwork

Abstract

The invention discloses a method for vertical combination construction of a composite stratum underground continuous wall and a cast-in-situ bored pile, which comprises the following steps: (1) and (3) groove wall reinforcement and guide wall construction: two sides of the underground continuous wall are reinforced by adopting double-shaft stirring piles, and the guide wall is in an inverted L shape; (2) constructing the groove section and the pile hole of the diaphragm wall: circularly constructing by using a trenching machine and a rotary drilling rig, and cleaning sediments after the construction of the trench section and the pile hole of the diaphragm wall is completed; (3) integrally hoisting the manufactured ground wall reinforcement cage and the pile reinforcement cage, and removing sediments in the groove section of the ground wall and the pile hole again after hoisting is finished; (5) the concrete is poured by adopting a conduit method, and the wall pile is integrally poured at one time. According to the construction method provided by the invention, the bored pile is arranged at the bottom of the underground continuous wall, the wall piles are vertically combined, and the rock-socketed depth of the underground continuous wall is replaced by the rock-socketed depth of the pile, so that the rapid grooving in a soft and hard combined stratum is realized, the difficult problem of rock-socketed construction of the underground continuous wall is solved, and the construction is economically and efficiently completed.

Description

Method for vertical combination construction of composite stratum underground continuous wall and cast-in-situ bored pile
Technical Field
The invention belongs to the technical field of underground engineering, and particularly relates to a method for vertical combination construction of a composite stratum underground continuous wall and a cast-in-situ bored pile.
Background
Underground diaphragm wall excavation technology has its origin in europe. The method is developed according to the methods of using mud and pouring concrete underwater for well drilling and oil drilling, firstly wall protection mud underground continuous walls are adopted for construction in Milan Italy in 1950, and the technology is popularized in developed countries in the West and the former Soviet Union in the 50-60 th century, and becomes an effective technology in underground engineering and deep foundation construction.
The underground continuous wall is a foundation engineering, and adopts a trenching machine on the ground, and under the condition of slurry wall protection, a long and narrow deep groove is excavated along the peripheral axis of the deep excavation engineering, after the groove is cleaned, a steel reinforcement cage is hung in the groove, then underwater concrete is poured by using a conduit method to construct a unit groove section, and the steps are carried out section by section, so that a continuous reinforced concrete wall is constructed underground to be used as a structure for intercepting water, preventing seepage, bearing and retaining water. The construction vibration is small, the wall rigidity is large, the integrity is good, the construction speed is high, the earth and stone space can be saved, and the method can be used for constructing deep foundation pit support in dense building groups and carrying out reverse construction. The method is suitable for building basements, underground shopping malls, parking lots, underground oil depots, retaining walls, deep foundations of high-rise buildings, reverse construction building enclosures, deep pools, pits, vertical shafts and the like of industrial buildings.
With the development of economy in China, major cities establish urban rail transit engineering, at present, the construction technology for constructing underground continuous walls in soft soil layers in China is quite mature, but in soft and hard combined strata, the construction technology for rock-embedded underground continuous walls is still in the initial development stage, and the information in the aspects of application and practice is very limited. It is expected that in order to meet the requirement of urbanization development, as more and more underground spaces are developed and utilized, more and more underground continuous walls are required to be constructed under rock-socketed or more difficult conditions.
The double-wheel slot milling machine is applied and compared in rock-entering underground diaphragm wall construction in soft soil areas in China. The grooving construction efficiency of the double-wheel grooving machine is high, but the grooving cost and the in-and-out-of-site cost are high; the punching pile machine has slow construction footage and long period, and the vibration has large disturbance to the wall of the pile, so that the punching pile machine is not suitable for construction in the place close to a building, in particular to soft soil areas such as silt and the like.
Disclosure of Invention
The invention aims to provide a method for vertically combining and constructing an underground continuous wall and cast-in-place piles in a composite stratum.
In order to achieve the purpose, the invention adopts the technical scheme that:
a method for vertical combination construction of a composite stratum underground continuous wall and a cast-in-situ bored pile comprises the following steps:
(1) and (3) groove wall reinforcement and guide wall construction: two sides of the groove section of the underground diaphragm wall are reinforced by adopting double-shaft stirring piles, the guide wall is in an inverted L shape, and concrete supports of 0.3 multiplied by 0.3mC30 are arranged in the guide wall at a horizontal interval of 3m and a vertical interval of 1m in a vertical crossed manner;
(2) constructing the groove section and the pile hole of the diaphragm wall: combining the length of each underground continuous wall, accurately positioning the central position of a bored pile on the guide wall surface, marking, excavating the groove section of the underground continuous wall in steps by adopting a trenching machine, grabbing to a position 3-5 meters above the designed elevation of the wall bottom to stop excavating, and reserving a sticky soil layer with the thickness of 3-5 meters as a guide soil layer of the rotary drilling rig to ensure the hole forming position and the verticality of the rotary drilling rig; drilling a hole in the rock layer by using a rotary drilling rig, grabbing the rest guide soil layer by using a trenching machine after the pile hole is formed by drilling, and finally removing sediments in the groove section of the diaphragm wall and the pile hole;
(3) hoisting a steel reinforcement cage: integrally hoisting the manufactured ground wall reinforcement cage and the pile reinforcement cage, and putting the ground wall reinforcement cage and the pile reinforcement cage into the groove section and the pile hole of the ground wall; after the hoisting is finished, removing sediments in the groove sections and pile holes of the diaphragm wall again; the integral type steel reinforcement cage that ground even wall steel reinforcement cage and stake steel reinforcement cage are constituteed: the pile reinforcement cage comprises a ground continuous wall reinforcement cage and a pile reinforcement cage which are fixedly connected, wherein the upper part of the pile reinforcement cage is embedded into the ground continuous wall reinforcement cage; the top of the underground diaphragm wall reinforcement cage is in a bell mouth shape; the top of the pile cage is fixed with guide bars. The underground continuous wall reinforcement cage comprises underground continuous wall longitudinal main reinforcements, underground continuous wall transverse distribution reinforcements, underground continuous wall transverse trusses and underground continuous wall longitudinal trusses which are arranged in a staggered mode. Continuously arranged X-shaped longitudinal reinforcing steel bars are welded inside the ground continuous wall longitudinal truss, and continuously arranged X-shaped transverse reinforcing steel bars are welded inside the ground continuous wall transverse truss; the X-shaped longitudinal reinforcing steel bars and the X-shaped transverse reinforcing steel bars can improve the integral rigidity of the structure.
The pile cage includes a plurality of vertical cage bars, helical bars surrounding the vertical cage bars, and reinforcing stirrups. The vertical main reinforcement is phi 32HRB400 steel bars, and the spiral reinforcement is at @ 100-250 phi 14HRB400 steel bars; connecting steel bars are welded between the pile steel reinforcement cage and the ground wall steel reinforcement cage, and the top of the pile steel reinforcement cage is anchored in the ground wall steel reinforcement cage.
(4) Pouring concrete: and (3) pouring concrete by adopting a conduit method, and integrally pouring and molding the underground continuous wall and the cast-in-situ bored pile at one time to finally form a structure for vertically combining the underground continuous wall and the cast-in-situ bored pile.
In the step (1), the depth of the groove wall reinforcement is 1m to 9m below the ground, and the cement for the groove wall reinforcement is ordinary portland cement. The cement mixing amount is 15%, the water cement ratio is 1.2-1.5, and the grouting pressure is 0.4-0.6 MPa; the thickness of the guide wall is 200-250 mm, the depth of the guide wall is 1.8-2.0 m, the guide wall is larger than 0.4m when entering into undisturbed soil, the main rib of the guide wall adopts HRB400 phi 14@200, and the distributed steel bar adopts HRB400 phi 12@ 200.
In the step (2), steel plates are laid under the caterpillar tracks of the grooving machine when the grooving machine is used for constructing the underground diaphragm wall groove section, and sacks are padded under the steel plates. So as to reduce the influence on the ground vibration and correspondingly reduce the influence on the groove wall. In the construction process, the grab bucket follows the principle that: the slow release is gently promoted, and the brute force is strictly prohibited. Before the groove section of the diaphragm wall is constructed, geological reconnaissance is carried out in the groove section every 10-12 meters, coring is carried out until the depth of a rock stratum is not less than 1m, and different rock stratum depths are accurately determined; during the drilling process of the rotary drilling rig, temporary section steel supports are arranged at two ends of the guide wall, so that the deformation of the guide wall is reduced.
In the step (2), a parallel gas lift reverse circulation hole cleaning method is adopted for removing sediments at the bottom of the hole and in the hole. The gas lift reverse circulation hole cleaning conduit needs to be sealed, and air leakage cannot occur. And cleaning the holes of each wall according to three positions, firstly cleaning the walls, then piling and gradually lowering the guide pipe, so that sediment is prevented from blocking the guide pipe in the hole cleaning process, and finally, the hole cleaning effect is best when the lower part of the pipe orifice is 0.1m away from the bottom of the hole or the hole bottom. In the hole cleaning process, the guide pipe is moved up and down, so that the hole cleaning efficiency is improved.
Further, in the step (2), the stability of the slurry liquid level is kept in the construction process of the underground diaphragm wall groove section and the pile hole, the slurry liquid level is kept 0.2-0.4 m below the guide wall surface, and the slurry is supplemented in time in the process. The mud reserve satisfies the usage of 2 slots. For holes with longer standing time after hole forming, the specific gravity of the slurry at the bottom is larger, the new slurry is uniformly mixed in the holes by positive circulation, and then the holes are cleaned by reverse circulation, and the new slurry is added while the slag is cleaned until the indexes of the sediment and the slurry meet the requirements.
In the step (3), the sediment in the slot section of the diaphragm wall and the pile hole is removed again by adopting a hole cleaning method combining built-in gas lift reverse circulation and positive circulation.
The beneficial effects provided by the invention are as follows:
(1) the invention aims to provide a method for vertically combining and constructing an underground continuous wall and cast-in-place piles in a composite stratum.
(2) The method provides the construction parameters of the slot section and the pile hole of the diaphragm wall and the combined construction measure of the diaphragm wall and the cast-in-situ bored pile, is economic and reasonable, simple to operate and low in cost, and provides technical parameters for the rock-socketed enclosure system of the underground engineering and the similar engineering in the future.
Drawings
FIG. 1 is a sectional view of a system combining an underground diaphragm wall and a cast-in-situ bored pile;
FIG. 2 is a schematic diagram of a pile hole location of a cast-in-situ bored pile;
FIG. 3 is a schematic diagram of a first stage of diaphragm wall groove section and pile hole construction;
FIG. 4 is a schematic diagram of a second stage of the trench section and pile hole construction of the diaphragm wall;
FIG. 5 is a schematic diagram of a third stage of the construction of the trench section and the pile hole of the diaphragm wall;
fig. 6 is a front view of an integrated reinforcement cage consisting of an underground wall reinforcement cage and pile reinforcement cages;
fig. 7 is a side view of an integrated reinforcement cage of an underground wall reinforcement cage and pile reinforcement cages;
fig. 8 is a top plan view of an integrated reinforcement cage consisting of an underground wall reinforcement cage and pile reinforcement cages;
figure 9 is a diagram of the pile cage reinforcement;
FIG. 10 is a cross-sectional view taken along line B-B of FIG. 9;
FIG. 11 is a cross-sectional view taken along line A-A of FIG. 9;
reference numerals: 1-underground continuous wall, 101-underground continuous wall groove section, 2-bored pile, 201-pile hole, 3-channel steel, 4-pile protection point, 5-grooving machine hydraulic grabbing head, 6-bentonite slurry, 7-clay layer, 8-rock layer, 9-rotary drilling rig, 10-vertical main rib, 11-spiral rib, 12-reinforced stirrup, 13-underground continuous wall longitudinal main rib, 14-underground continuous wall transverse distribution rib, 15-connecting steel bar, 16-underground continuous wall longitudinal truss, 17-underground continuous wall transverse truss, 18-guide steel bar, 19- 'X' -shaped longitudinal reinforced steel bar and 20- 'X' -shaped transverse reinforced steel bar.
Detailed Description
The present invention will be further described with reference to the following examples. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Engineering background
The Ningbo city rail transit 2 # line second-stage civil engineering red united station is a T-shaped transfer station of 2 # line and 6 # line, an underground continuous wall supporting system is adopted, wherein the deepest underground continuous wall reaches 55m, 25 rock-entering lines are counted on the 6 # line, 15 rock-entering lines are counted on the 2 # line, the underground continuous wall is embedded with the strongly weathered rock not less than 2m, the pile is embedded with the strongly weathered rock not less than 3.5m, or the embedded moderately weathered rock not less than 2.5 m.
The strongly weathered crystal chip and glass chip are sintered to form tuff, the weathering is stronger, the joint cracks develop, the crack surfaces are stained by ferro-manganese substances, the rock core is in a broken block shape and a block shape, the rock core is knocked to be dumb, the rock belongs to extremely soft rock, the natural compressive strength of the rock is less than 5.0MPa, and the basic quality grade of the rock is V. The moderately weathered crystal filings and glass scraps are sintered and coagulated into tuff, the rock mass is hard, the average value is 62.04MPa, the standard value is 53.28MPa, and the tuff belongs to hard rock. The soft soil with the sludge layer distributed on the upper part has the characteristics of high natural water content, high compressibility, strong thixotropy, strong rheological property, low strength, low water permeability and the like, and belongs to a typical composite stratum with soft upper part and hard lower part.
Aiming at the composite stratum, according to the stress characteristics of a foundation pit enclosure system, the invention adopts a stratum underground continuous wall and cast-in-situ bored pile vertical combination system, as shown in figure 1, namely two phi 1000 cast-in-situ bored piles 2 are arranged at the bottom of an underground continuous wall 1, and the two cast-in-situ bored piles 2 are respectively positioned at one third of the length of the underground continuous wall 1, so that the stress is uniform; according to the strength and the integrity of the rock stratum, the depth of embedding the wall and the pile into different rock strata is determined, and the integral stability of the foundation pit is ensured. The bottom of the underground continuous wall is embedded with strongly weathered rock 2m, and the piles are embedded into rock layers.
The invention adopts a method for vertically combining and constructing an underground continuous wall and a cast-in-situ bored pile, which comprises the following steps as shown in figures 1-5:
(1) and (3) groove wall reinforcement and guide wall construction:
and reinforcing two sides of the groove section of the diaphragm wall by using phi 700@500mm double-shaft stirring piles, wherein the reinforcing depth of the groove wall is 1-9 m below the ground. The tank wall reinforced cement is P.O42.5 ordinary Portland cement, and the cement mixing amount is 15 percent;
the guide wall adopts an inverted L shape, C25 concrete is adopted, and the distance from the guide wall to the undisturbed soil is more than 0.4 m. The main reinforcing steel bars of the guide wall adopt HRB400 phi 14@200, and the distributed reinforcing steel bars adopt HRB400 phi 12@ 200; the guide wall is internally provided with 0.3 multiplied by 0.3mC30 concrete supports which are arranged in a vertical cross mode at a horizontal interval of 3m and a vertical interval of 1 m.
(2) Constructing the groove section and the pile hole of the diaphragm wall:
accurately positioning the central position of the cast-in-situ bored pile 2 on the guide wall surface by combining the length of each underground continuous wall 1, and limiting and marking the notch of the groove section of the underground continuous wall by using a No. 10 channel steel 3;
the underground diaphragm wall groove section 101 is grooved by a grooving machine according to three steps, the two sides are grooved firstly and then the middle is grooved, the hydraulic grabbing head 5 of the grooving machine grabs to a position 3-5 meters above the designed elevation of the wall bottom to stop excavating, a clay layer 7 with the thickness of about 3-5 meters is reserved as a guide soil layer of a rotary drilling rig, and the hole forming position and the perpendicularity of the rotary drilling rig 9 are ensured;
and (3) accurately aligning the rotary drilling rig 9 at the notch with an error smaller than 5cm, and vertically lowering the drill rod to the bottom of the groove. Dig rig 9 soon and control according to normal speed and parameter at clay layer 7, need change the drill bit according to actual conditions when boring to rock layer 8, wherein: drilling in the strongly weathered rock by adopting a cutting tooth barrel drill, slowly pressurizing to drill, controlling the drilling pressure to be 1-5 MPa, controlling the drilling speed to be 0.3-0.5 m/h, lifting the drill bit once every 30cm of drilling, and circularly drilling until the strongly weathered rock is drilled into the middle weathered rock surface;
the method comprises the steps of enabling a rotary drilling rig to drill weathered rock with the depth of 30cm or less in the drilling process to be replaced by an alloy roller bit, continuing to drill in weathered rock, gradually pressurizing and drilling, controlling the drilling pressure to be 25-30 MPa, the drilling speed to be 0.1-0.2 m/h, and drilling with the cylinder at the speed of 0.6-0.8 m each time, and then drilling with the cylinder to remove rock layers. Circulating to the designed pile bottom elevation finally; detecting the pile hole by adopting ultrasonic waves, detecting the pile hole by adopting a 4m long detection cage with the diameter of 0.6m according to an ultrasonic detection image, accurately determining the actual position of the pile hole 201, and marking on the guide wall surface;
the remaining guide soil layer is grabbed and removed by a hydraulic grabbing head 5 of a grooving machine, the grooving machine is used for grabbing and removing the guide soil layer to the designed toe elevation, the guide soil layer flows into a pile hole for settling slag in the grooving process, a drilling machine is used for removing the slag again, the stability of the slurry liquid level is kept in the construction process of the underground diaphragm wall groove section 101 and the pile hole 201, the slurry is bentonite slurry 6, high-quality sodium-level bentonite is used for making slurry, and all indexes meet the standard requirement; and finally, removing sediments in the slot sections and pile holes of the diaphragm wall, and adopting a parallel gas lift reverse circulation hole cleaning method, which comprises the following specific steps:
removing sediments in the order of groove and hole, wherein the diameter of the discharged slag is phi 250 steel pipe, the wall thickness is 6mm, the gas pipe is phi 50, the distance from the bottom of the steel pipe is 0.5m, and the gas pressure is controlled to be 0.7-1 MPa; when cleaning holes, the gas lift reverse circulation hole cleaning guide pipe needs to be sealed, and air leakage cannot occur. Each wall is cleaned according to three positions, the hole is cleaned firstly and then the hole, the guide pipe is gradually put downwards, the guide pipe is prevented from being blocked by sediment in the hole cleaning process, and finally the hole cleaning effect is best when the lower part of the pipe opening is 0.1m away from the bottom of the hole or the hole bottom. In the hole cleaning process, the guide pipe is moved up and down, so that the hole cleaning efficiency is improved.
(3) Hoisting a steel reinforcement cage: integrally hoisting the manufactured ground wall reinforcement cage and the pile reinforcement cage, and putting the ground wall reinforcement cage and the pile reinforcement cage into the groove section and the pile hole of the ground wall; after the hoisting is finished, the sediment is removed by adopting the mutual combination of the built-in gas lift reverse circulation and the positive circulation. The structure of the integrated reinforcement cage consisting of the ground wall reinforcement cage and the pile reinforcement cage is shown in fig. 6-11: the pile reinforcement cage comprises a ground continuous wall reinforcement cage and a pile reinforcement cage which are fixedly connected, wherein the upper part of the pile reinforcement cage is embedded into the ground continuous wall reinforcement cage; the top of the underground diaphragm wall reinforcement cage is in a bell mouth shape; the top of the pile cage is secured to guide bars 18. The underground continuous wall reinforcement cage comprises underground continuous wall transverse distribution ribs 14, underground continuous wall longitudinal main ribs 13, underground continuous wall transverse trusses 16 and underground continuous wall longitudinal trusses 17 which are arranged in a staggered mode. Continuously arranged X-shaped longitudinal reinforcing steel bars 19 are welded inside the ground continuous wall longitudinal truss 16, and continuously arranged X-shaped transverse reinforcing steel bars 20 are welded inside the ground continuous wall transverse truss 16; the "X" type longitudinal reinforcing bars 19 and the "X" type transverse reinforcing bars 20 can improve the overall rigidity of the structure thereof.
The pile cage comprises a plurality of vertical cage bars 10, helical reinforcement bars 11 surrounding the vertical cage bars, and reinforcing stirrups 12. The vertical main reinforcement 10 is a phi 32HRB335 steel bar, and the spiral reinforcement 11 is a phi 100-250 phi 14HRB335 steel bar; connecting steel bars 15 are welded between the pile reinforcement cage and the ground wall reinforcement cage, and the top of the pile reinforcement cage is anchored in the ground wall reinforcement cage.
(4) Pouring concrete:
after all indexes are detected to be qualified, adopting a conduit method to pour concrete underwater, wherein the diameter of the conduit is phi 250, adopting screw threads to connect, and inclining the bottom of the first section of conduit by 60 degrees to perform a cutting treatment; reasonably configuring a guide pipe according to the depth of the pile hole, wherein the guide pipe is required to extend into the pile hole, and the length of the first section of guide pipe is the same as that of the pile hole; concrete pouring ensures continuity, the volume of the first concrete plate ensures that the guide pipe is embedded 2m above the bottom of the underground continuous wall, and the first guide pipe is removed in time after the first concrete plate is poured; in the process of pouring concrete, the guide pipe is removed in time along with the pouring of the concrete; and integrally pouring and forming the underground continuous wall and the cast-in-situ bored pile at one time to finally form a structure of vertically combining the underground continuous wall and the cast-in-situ bored pile.
As a preferred embodiment, the method provided by the present invention also needs to pay attention to the following points during the construction process:
(1) when the trenching machine is constructed, a steel plate is laid under the caterpillar track, and a gunny bag is padded under the steel plate. So as to reduce the impact on the ground vibration and correspondingly reduce the impact on the groove wall. In the construction process, the grab bucket follows the principle that: the slow release is gently promoted, and the brute force is strictly prohibited. Before the groove section of the diaphragm wall is constructed, geological reconnaissance is carried out in the groove section every 10-12 meters, coring is carried out until the depth of a rock stratum is not less than 1m, and different rock stratum depths are accurately determined; during the drilling process of the rotary drilling rig, temporary section steel supports are arranged at two ends of the guide wall, so that the deformation of the guide wall is reduced.
(2) In the drilling process of a rock stratum, particularly on a soft and hard interface surface, the rotary drilling rig needs to drill at low speed and low pressure, the perpendicularity of a pile position is guaranteed, the drilling depth is controlled to be 0.3-0.6 m each time, and the rotary drilling rig is not easy to drill to the bottom at one time.
(3) The width of the underground diaphragm wall is not more than 6m, double-guide-pipe concrete pouring is adopted, the positions of the guide pipes and the pile holes are guaranteed to be consistent and are positioned at one third of the auxiliary width, when the width is more than 6m, three guide pipes are adopted for pouring concrete, one guide pipe is additionally arranged between two pile holes, and the third guide pipe is poured by matching the automobile pump with the concrete.
(4) The steel reinforcement cage of stake, the top sets up phi 10 guide reinforcing bar, prevents that the pipe from transferring the in-process and hanging the reinforcing bar, and the steel reinforcement cage central point of stake puts and carries out the sign on secret continuous wall reinforcing bar, puts the in-process under to the counterpoint.
(5) In the construction process of the underground diaphragm wall groove section and the pile hole, high-quality bentonite is adopted for making slurry, the stability of the slurry liquid level is kept, the slurry liquid level is kept 0.2-0.4 m below the guide wall surface, and the slurry is supplemented in time in the process. The mud reserve satisfies the usage of 2 slots. For holes with longer standing time after hole forming, the specific gravity of the slurry at the bottom is larger, the new slurry is uniformly mixed in the holes by positive circulation, and then the holes are cleaned by reverse circulation, and the new slurry is added while the slag is cleaned until the indexes of the sediment and the slurry meet the requirements.
(6) The construction of the rock-socketed underground diaphragm wall strengthens equipment management and maintenance work, ensures the continuity of each construction, and shortens the connection time among all working procedures as much as possible. In the construction process, the monitoring on the surrounding environment is enhanced.

Claims (6)

1. The method for vertical combined construction of the composite stratum underground continuous wall and the cast-in-situ bored pile is characterized by comprising the following steps of: the method comprises the following steps:
(1) and (3) groove wall reinforcement and guide wall construction: two sides of the groove section of the underground diaphragm wall are reinforced by adopting double-shaft stirring piles, the guide wall is in an inverted L shape, and concrete supports are arranged in the guide wall;
(2) constructing the groove section and the pile hole of the diaphragm wall: accurately positioning the central position of the bored pile on the guide wall surface to mark by combining the length of each underground continuous wall, excavating the groove section of the underground continuous wall in steps by adopting a trenching machine, grabbing to a position 3-5 meters above the designed elevation of the wall bottom of the underground continuous wall to stop excavating, and reserving a clay layer with the thickness of 3-5 meters as a guide soil layer of the rotary drilling rig; drilling a hole in the rock layer by using a rotary drilling rig, grabbing the rest guide soil layer by using a trenching machine after the pile hole is formed by drilling, and finally removing sediments in the groove section of the diaphragm wall and the pile hole;
(3) hoisting a steel reinforcement cage: integrally hoisting the manufactured ground wall reinforcement cage and the pile reinforcement cage, and putting the ground wall reinforcement cage and the pile reinforcement cage into the groove section and the pile hole of the ground wall; after the hoisting is finished, removing sediments in the groove sections and pile holes of the diaphragm wall again;
(4) pouring concrete: and (3) pouring concrete by adopting a conduit method, and integrally pouring and molding the underground continuous wall and the cast-in-situ bored pile at one time to finally form a structure for vertically combining the underground continuous wall and the cast-in-situ bored pile.
2. The method of claim 1, wherein: in the step (1), the depth of the groove wall reinforcement is 1m to 9m below the ground, and the groove wall reinforcement cement is P.O42.5-grade ordinary portland cement; the thickness of the guide wall is 200-250 mm, the depth of the guide wall is 1.8-2.0 m, and the thickness of the guide wall entering undisturbed soil is more than 0.4 m.
3. The method of claim 1, wherein: in the step (2), when the trenching machine is constructed, a steel plate is laid under the caterpillar track of the trenching machine, and a jute bag is padded under the steel plate; before the construction process of the underground diaphragm wall groove section, geological reconnaissance is carried out in the underground diaphragm wall groove section every 10-12 m, coring is carried out until the depth of a rock stratum is not less than 1m, and different rock stratum depths are accurately determined; during the drilling process of the rotary drilling rig, temporary section steel supports are arranged at two ends of the guide wall, so that the deformation of the guide wall is reduced.
4. The method of claim 1, wherein: and (3) in the step (2), removing sediments in the slot sections and pile holes of the diaphragm wall by adopting a parallel gas lift reverse circulation hole cleaning method.
5. The method of claim 1, wherein: in the step (2), the stability of the slurry liquid level is kept in the construction process of the underground diaphragm wall groove section and the pile hole, the slurry liquid level is kept 0.2-0.4 m below the guide wall surface, and the slurry is supplemented in time in the process.
6. The method of claim 1, wherein: and (3) removing sediments in the slot section of the diaphragm wall and the pile hole again by adopting a hole cleaning method combining built-in gas lift reverse circulation and positive circulation.
CN202010723971.4A 2020-03-27 2020-07-24 Method for vertical combination construction of composite stratum underground continuous wall and cast-in-situ bored pile Pending CN111705786A (en)

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