CN108425387B - Foundation reinforcing construction technology for building foundation - Google Patents
Foundation reinforcing construction technology for building foundation Download PDFInfo
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- CN108425387B CN108425387B CN201810325126.4A CN201810325126A CN108425387B CN 108425387 B CN108425387 B CN 108425387B CN 201810325126 A CN201810325126 A CN 201810325126A CN 108425387 B CN108425387 B CN 108425387B
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- 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
- E04G23/00—Working measures on existing buildings
- E04G23/02—Repairing, e.g. filling cracks; Restoring; Altering; Enlarging
- E04G23/0218—Increasing or restoring the load-bearing capacity of building construction elements
- E04G23/0229—Increasing or restoring the load-bearing capacity of building construction elements of foundations or foundation walls
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D37/00—Repair of damaged foundations or foundation structures
Abstract
The invention discloses a foundation reinforcing construction method for building foundation, which is characterized in that the following technical scheme is adopted for reinforcing the foundation by adopting flexible piles such as cement mixing piles: the method comprises the following steps that a raft foundation is adopted as a foundation of a house after transformation, I-shaped steel is inserted into part of cement mixing piles, and the length of the I-shaped steel is 1.8-2.5 times that of the cement mixing piles; a post-cast hole is arranged at the position where the I-shaped steel is arranged, and the diameter of the post-cast hole is the same as that of the cement mixing pile; rubber blocks are laid on the I-shaped steel, reinforcing ribs are arranged at the post-pouring hole, and stirrups with the spacing of 200mm are arranged at the same time.
Description
Technical Field
The invention relates to a house reinforcing structure, in particular to a foundation reinforcing construction technology for building and demolishing a house foundation.
Background
With the development of urban construction, some dangerous and old houses need to be transformed, the number of layers of the original dangerous and old houses is generally lower, the load transmitted to the foundation is smaller, and therefore the bearing capacity after the foundation is processed is relatively lower. The number of layers of the reformed house is possibly much higher than that of the original dangerous house, the load transmitted to the foundation is also larger, and the foundation needs to be reprocessed to meet the requirement of bearing capacity. Because the pile foundation of original dangerous and old house and the pile foundation of house after reforming transform have great difference, if handle improperly and cause local foundation to warp inhomogeneous easily, cause inhomogeneous settlement.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a foundation reinforcing construction technology for building and demolishing a house foundation to ensure that the house settlement and the bearing performance meet the requirements.
The foundation treatment of the dangerous and old house has two forms: firstly, a rigid pile such as a concrete pile is adopted for reinforcement, and the foundation type is usually a bearing platform foundation; and secondly, flexible piles such as cement mixing piles are adopted for reinforcement, and the foundation type is usually a raft foundation. The invention adopts different technical schemes aiming at different pile foundation forms.
For the foundation reinforced by rigid piles such as concrete piles, the following technical scheme is adopted:
in order to improve economic benefit, original pile foundations and concrete foundations are utilized as far as possible. Because the height of the bearing platform is relatively high, after the raft foundation is transformed from the foundation structure form, if the height of the raft foundation is the same as that of the bearing platform, the raft foundation is relatively wasted, and the bearing platform can be properly cut down. The raft foundation is adopted as the foundation of the house after transformation, the thickness of the raft foundation is 600-800 mm, the raft foundation is composed of a reduced bearing platform and a newly poured foundation, the lower reinforcing steel bar of the newly poured foundation adopts a reinforcing steel bar with the diameter of 20-25 mm, the interval of the reinforcing steel bars is 150-200 mm, the bearing platform and the newly poured foundation are connected into a whole through connecting bars, the interval of the connecting bars is 200-250 mm, the diameter of the connecting bars is 22-25 mm, the length of the connecting bars extending into the embedded holes of the bearing platform is 250-300 mm, the diameter of the embedded holes of the bearing platform is 24-27 mm, gaps between the connecting bars and the embedded holes of the bearing platform are filled with epoxy resin, and the connecting bars are exposed out of the bearing platform and are 400-450 mm. And a post-cast hole is arranged in the bearing platform, and the diameter of the post-cast hole is the same as that of the concrete pile.
Original concrete pile arranges with the cushion cap form usually, arranges minor diameter concrete pile outside the cushion cap, and minor diameter concrete pile diameter is 150 ~ 300mm, sets up the block rubber at concrete pile bolck, and block rubber thickness is 100 ~ 150 mm. The small-diameter concrete pile head is provided with a precast concrete pipe hoop, the height of the precast concrete pipe hoop embedded into the small-diameter concrete pile head is 100mm, and the top of the precast concrete pipe hoop is 120-150 mm higher than the small-diameter concrete pile head. The gravel sand cushion is laid on the top of the small-diameter concrete pile, the thickness of the gravel sand cushion is 120-150 mm, the length of the small-diameter concrete pile can be the same as that of the concrete pile, if a hard layer is arranged on a shallow part under site geological conditions, the small-diameter concrete pile can stretch into the shallow hard layer by 500-800 mm and form a long-short pile structure with the concrete pile, the shallow hard layer is generally 10-20 m, and the deep hard layer into which the concrete pile stretches is generally a soil layer more than 20 m.
The gravel sand cushion layer is arranged on the small-diameter concrete pile so as to enable the small-diameter concrete pile and the soil to have better synergistic effect, the rigidity of the small-diameter concrete pile is very large, the soil is relatively small, the stress of the small-diameter concrete pile can be large under the same strain, the soil stress can be small, and the rigidity ratio of the small-diameter concrete pile and the surrounding soil body can be effectively reduced by laying the gravel sand cushion layer on the top of the small-diameter concrete pile. In order to prevent the gravel sand cushion layer from horizontally moving under the action of upper load and overflowing into the surrounding soil body to lose balance stress, a precast concrete pipe hoop is nested on the pile top of the small-diameter concrete pile.
The quantity of the small-diameter concrete piles is dually controlled according to the bearing capacity requirement and the settlement control requirement, the quantity of the small-diameter concrete piles is preliminarily determined according to the bearing capacity, the quantity S of the small-diameter concrete piles is determined according to the following formula, and S is equal to m2Az/Ap2，AzIs the area of the bottom of the raft foundation, m2Is the replacement rate of the small-diameter concrete pile, namely the ratio of the total cross-sectional area of the pile to the bottom area of the raft foundation, Ap2The sectional area of the small-diameter concrete pile and the replacement rate m of the small-diameter concrete pile2Determined according to the formula, f ═ m1R1/Ap1+(Ec2/Ec1)m2R2/Ap2+θ(Es/Ec1)fsIn the formula m1Is the replacement rate of the concrete pile, namely the ratio of the total sectional area of the concrete pile to the bottom area of the raft foundation, R1For the bearing capacity of the concrete pile, Ap1Is the cross-sectional area of the concrete pile, Ec1Is the modulus of elasticity of the concrete pile, Ec2Is the elastic modulus m of a small-diameter concrete pile2Is the replacement rate, R, of the small-diameter concrete pile2Bearing capacity of small diameter concrete pile, Ap2The sectional area of the small-diameter concrete pile is taken, theta is a reduction coefficient, and E is 0.5-0.6sIs the modulus of elasticity of the soil, fsThe bearing capacity of the soil foundation.
And (4) primarily determining the number of the small-diameter concrete piles according to the bearing capacity requirement, and then performing settlement rechecking. The settlement calculation formula is as follows:
First part complex modulus Es1The calculation formula is as follows: es1＝m1Ec1+m2Ec2+(1-m1-m2)EsSecond part composite modulus Es2The calculation formula is as follows: es2＝m1Ec1+(1-m1)Es。
And if the settlement exceeds 100mm, increasing the length and the number of the small-diameter concrete piles to perform re-settlement and rechecking until the settlement meets the requirement.
The construction steps comprise:
(1) chiseling concrete at the position, higher than the top elevation of the newly-poured foundation, of an original bearing platform to 150mm below the top elevation of the newly-poured foundation, cutting off redundant steel bars at the upper part, welding small stirrups to the stirrups at the lower part, wherein the heights of the small stirrups are 100mm, the diameters of the steel bars adopted by the small stirrups are 8mm, the intervals are 50-100 mm, and erecting stressed steel bars on the small stirrups and binding and fixing the steel bars;
(2) chiseling out the concrete at the concrete pile part of the original bearing platform and then pouring a hole, and cutting down the pile top of the concrete pile, wherein the elevation of the pile top of the concrete pile is 100-150 mm lower than that of the bottom of the original bearing platform; the concrete pile top reinforcing steel bars usually extend into an original bearing platform by 50cm, and after the concrete pile top is cut down to be in place, the exposed reinforcing steel bars of the concrete pile top are cut off to be flush with the concrete pile top after the concrete pile top is cut down to be in place;
(3) constructing small-diameter concrete piles between the bearing platforms, wherein the pile top elevation of the small-diameter concrete piles is 50-100 mm lower than the bottom elevation of the original bearing platform;
(4) sleeving a precast concrete pipe hoop on the pile top of the small-diameter concrete pile;
(5) paving a gravel sand cushion layer on the pile top of the small-diameter concrete pile;
(6) drilling a reserved hole by using an electric drill, inserting a connecting rib into the reserved hole, and sealing a gap between the reserved hole and the connecting rib by using epoxy resin;
(7) binding newly-poured foundation steel bars, erecting a newly-poured foundation template, pouring newly-poured foundation concrete, and pouring concrete at the position, lower than the top elevation of the newly-poured foundation, of the bearing platform;
(8) after the concrete pile is lowered to the proper position, paving a rubber block on the pile top of the concrete pile;
(9) after the house reaches three layers, the post-cast hole is sealed by the expanded concrete; because the concrete pile is easy to bear firstly under the action of upper load, the bearing capacity of the small-diameter concrete pile, particularly the bearing capacity of the concrete, is difficult to exert, the post-cast hole is sealed after the house reaches three layers, so that the small-diameter concrete pile and the concrete participate in bearing firstly, and the cooperative bearing capacity of the concrete pile, the small-diameter concrete pile and the concrete can be further enhanced after the number of layers is increased.
To adopting flexible stake to carry out the basis of consolidating like cement mixing stake, adopt following technical scheme:
the foundation of house after transformation adopts raft foundation, and raft foundation thickness is 600 ~ 800 mm. In order to improve the bearing capacity and the deformation resistance of the foundation, I-shaped steel is inserted into part of the cement mixing piles, and the length of the I-shaped steel is 1.8-2.5 times that of the cement mixing piles. And a rear pouring hole is arranged at the position where the I-shaped steel is arranged, and the diameter of the rear pouring hole is the same as that of the cement mixing pile. In order to avoid stress concentration in the stress process, rubber blocks are laid on the I-shaped steel, and the thickness of each rubber block is 150-200 mm. The anti-shear force that the back gate position received can be great after the I-steel bore load, so set up the strengthening rib at the back gate position, the strengthening rib is 4 reinforcing bars that the diameter is 25mm, sets up the stirrup that the interval is 200mm simultaneously, and the stirrup diameter is 8 mm.
The number of the I-beams is dual controlled according to the bearing capacity requirement and the settlement control requirement, the number of the I-beams is preliminarily determined according to the bearing capacity, the number G of the I-beams is determined according to the following formula, G is m2gAz/Ap2g，AzIs the area of the bottom of the raft foundation, m2gIs the replacement rate of I-shaped steel, i.e. the ratio of the total cross-sectional area of the pile to the bottom area of the raft foundation, Ap2gIs the cross section area of the I-steel and the replacement rate m of the I-steel2gIs determined according to the following formula,
f＝m1sR1s/Ap1s+(Ec2g/Ec1s)m2gR2g/Ap2g+3(Es/Ec1s)fsin the formula m1sIs the replacement rate of the cement mixing pile without inserted I-steel, namely the ratio of the total cross section area of the cement mixing pile without inserted I-steel to the bottom area of the raft foundation, R1sFor the bearing capacity of the cement mixing pile, Ap1sThe cross section of the cement mixing pile Ec1sIs the elastic modulus of the cement mixing pile, Ec2gIs the modulus of elasticity, m, of the I-steel2gIs the rate of replacement of I-steel, R2gBearing capacity of I-steel, Ap2gThe sectional area of the I-shaped steel is taken as the coefficient of reduction of β, and E is taken as 0.7-0.8sIs the modulus of elasticity of the soil, fsThe bearing capacity of the soil foundation.
And (4) performing settlement rechecking after preliminarily determining the number of the I-shaped steel according to the bearing capacity requirement. The settlement calculation formula is as follows:
where p is the stress transmitted from the upper part to the foundation, EsiIs the complex modulus, ziAnd zi-1The depth of the basal bottom surface is respectively within the range of the bottom surface of the ith layer and the ith-1 layer,
and
the average additional stress coefficient from the bottom surface of the foundation to the bottom surfaces of the ith and (i-1) th layers is determined according to the technical Specification for treating building foundations (JGJ-79-91), the composite modulus of the whole foundation can be divided into three parts along the depth direction, the first part is the foundation formed by cement mixing piles, I-shaped steel and soil, the second part is the foundation formed by the I-shaped steel and the soil, and the third part is the foundation formed by the soil of the lower lying layer.
First part complex modulus Es1sThe calculation formula is as follows: es1s＝m1sEc1s+m2gEc2g+(1-m1s-m2g)EsSecond part composite modulus Es2sThe calculation formula is as follows: es2s＝m2gEc2g+(1-m2g)Es。
And if the settlement exceeds 100mm, increasing the length and the number of the I-beams and performing re-settlement and rechecking until the settlement meets the requirement.
The construction steps comprise:
(1) chiseling out post-cast holes on raft concrete at the position where the I-shaped steel is installed, and cutting off redundant steel bars on the upper part;
(2) drilling an I-shaped groove in a cement mixing pile body by a drilling machine drilling tool through a rear pouring hole, mounting an I-shaped cutter at the head of the drilling machine to cut cement soil, hoisting an I-shaped steel by a crane, and ensuring the verticality by a positioning steel plate in the process of inserting the I-shaped steel into the I-shaped groove;
(3) and after the I-shaped steel is inserted, water glass is injected to seal a gap between the I-shaped steel and the I-shaped groove, and the injection pressure of the water glass is 1-1.2 MPa so as to ensure the grouting effect.
(4) Paving a rubber block on the top of the I-shaped steel;
(5) after the house reaches three layers, placing a reinforcement cage consisting of reinforcing ribs and stirrups into the post-pouring hole; the rigidity of the I-shaped steel is obviously much higher than that of the cement mixing pile or the rigidity of soil, so that the cement mixing pile is easy to bear firstly under the action of upper load, the bearing capacity, particularly the bearing capacity of soil, of the cement mixing pile is difficult to exert, the post-cast hole is sealed after the house reaches three layers, the cement mixing pile and the soil are firstly involved in bearing, and the cooperative bearing capacity of the cement mixing pile, the I-shaped steel and the soil can be further enhanced after the number of layers is increased.
(6) Pouring a post-pouring hole, wherein the post-pouring hole is made of expansive concrete; the pouring sequence of the post-pouring hole is that the periphery is firstly followed by the middle, and a symmetrical sealing mode is adopted as much as possible, so that the I-shaped steel is relatively uniform in bearing.
The invention has convenient construction operation, safety and reliability.
Drawings
Fig. 1 is a schematic view of a bearing platform, fig. 2 is a schematic view of an elevation of a raft foundation in the form of a foundation with rigid piles, fig. 3 is a schematic view of a plane of a raft foundation in the form of a foundation with rigid piles, and fig. 4 is a schematic view of a plane of a raft foundation in the form of a foundation with flexible piles.
1. The concrete pile comprises a bearing platform, 2 concrete piles, 3 rubber blocks, 4 post-cast holes, 5 connecting ribs, 6 small-diameter concrete piles, 7 prefabricated concrete pipe hoops, 8 gravel sand cushion layers, 9 newly-cast foundations, 10 cement mixing piles, 11 and I-steel.
Detailed Description
Example one
The basis in house adopts raft foundation after the transformation, raft foundation thickness is 700mm, raft foundation comprises back cushion cap 1 and the new foundation 9 of watering of cutting down, the steel bar that the diameter was 22mm is adopted to the new foundation 9 lower part reinforcing bar of watering, the reinforcing bar interval is 150mm, cushion cap 1 and the new foundation 9 of watering are connected into wholly through splice bar 5, the 5 intervals of splice bar are 200mm, the 5 diameters of splice bar are 22mm, splice bar 5 stretches into 1 pre-buried hole length of cushion cap and is 250mm, 1 pre-buried hole diameter of cushion cap is 24mm, the space adopts epoxy to clog between 5 and 1 pre-buried holes of cushion cap, 5 expose of splice bar in 1 length of cushion cap and be 400 mm. A post-cast hole 4 is arranged in the bearing platform 1, and the diameter of the post-cast hole 4 is the same as that of the concrete pile 2.
The small-diameter concrete pile 6 is arranged outside the bearing platform 1, the diameter of the small-diameter concrete pile 6 is 200mm, the rubber block 3 is arranged at the pile top of the concrete pile 2, and the thickness of the rubber block 3 is 120 mm. The pile head of the small-diameter concrete pile 6 is provided with a precast concrete pipe hoop 7, the height of the pile head of the small-diameter concrete pile 6, which is embedded into the precast concrete pipe hoop 7, is 100mm, and the top of the precast concrete pipe hoop 7 is 120mm higher than the pile top of the small-diameter concrete pile 6. Gravel sand cushion 8 is laid on 6 pile tops of minor diameter concrete pile, and gravel sand cushion 8 thickness is 120mm, and site geological conditions have the crust in the shallow portion of 15m, and minor diameter concrete pile 6 stretches into shallow portion crust 600mm, forms long and short pile structure with concrete pile 2.
The number of the small-diameter concrete piles 6 is dually controlled according to the bearing capacity requirement and the settlement control requirement, the number of the small-diameter concrete piles 6 is preliminarily determined according to the bearing capacity, the number S of the small-diameter concrete piles 6 is determined according to the following formula, and S is m2Az/Ap2，AzIs the area of the bottom of the raft foundation, m2Is the replacement rate of 6 small-diameter concrete piles, namely the ratio of the total cross-sectional area of the piles to the bottom area of the raft foundation, Ap2The sectional area of the small-diameter concrete pile 6 and the replacement rate m of the small-diameter concrete pile 62According to the followingFormula (i) is determined1R1/Ap1+(Ec2/Ec1)m2R2/Ap2+θ(Es/Ec1)fsIn the formula m1Is the replacement rate of the concrete pile 2, namely the ratio of the total sectional area of the concrete pile 2 to the bottom area of the raft foundation, R1For the bearing capacity of the concrete pile 2, Ap1Is the cross section area of the concrete pile 2, Ec1Is the modulus of elasticity of concrete pile 2, Ec2Is a small-diameter concrete pile 6 elastic modulus, m2Is the replacement rate, R, of the small-diameter concrete pile 62Is the bearing capacity of a small-diameter concrete pile 6, Ap2The sectional area of the small-diameter concrete pile 6 is taken, theta is a reduction coefficient, and E is 0.5-0.6sIs the modulus of elasticity of the soil, fsThe bearing capacity of the soil foundation.
And (4) primarily determining the number of the small-diameter concrete piles 6 according to the bearing capacity requirement, and then performing settlement rechecking. The settlement calculation formula is as follows:
First part complex modulus Es1The calculation formula is as follows: es1＝m1Ec1+m2Ec2+(1-m1-m2)EsSecond part composite modulus Es2The calculation formula is as follows: es2＝m1Ec1+(1-m1)Es。
And if the settlement exceeds 100mm, increasing the length and the number of the small-diameter concrete piles 6 to perform re-settlement and recheck until the settlement meets the requirement. According to the steps, the number of the I-beams 11 is determined to be 125.
The construction steps comprise:
(1) chiseling concrete at the position, higher than the top elevation of the newly cast foundation 9, of the original bearing platform 1 to 150mm below the top elevation of the newly cast foundation 9, cutting off redundant steel bars at the upper part, welding small stirrups to the stirrups at the lower part, wherein the heights of the small stirrups are 100mm, the diameters of the steel bars adopted by the small stirrups are 8mm, the intervals are 50-100 mm, and erecting stressed steel bars on the small stirrups and binding and fixing the steel bars;
(2) chiseling out the post-cast hole 4 of the concrete pile 2 part of the original bearing platform 1, cutting down the pile top of the concrete pile 2, and lowering the elevation of the pile top of the concrete pile 2 by 100-150 mm compared with the elevation of the bottom of the original bearing platform 1; cutting off exposed reinforcing steel bars at the pile top of the concrete pile 2 after the pile top of the concrete pile 2 is cut down to the proper position, and leveling the pile top of the concrete pile 2 after the pile top of the concrete pile 2 is cut down to the proper position;
(3) constructing small-diameter concrete piles 6 between the bearing platforms 1, wherein the pile top elevation of the small-diameter concrete piles 6 is 50-100 mm lower than the bottom elevation of the original bearing platform 1;
(4) sleeving a precast concrete pipe hoop 7 on the pile top of the small-diameter concrete pile 6;
(5) paving a gravel sand cushion layer 8 on the pile top of the small-diameter concrete pile 6;
(6) drilling a reserved hole by using an electric drill, inserting a connecting rib 5 into the reserved hole, and sealing a gap between the reserved hole and the connecting rib 5 by using epoxy resin;
(7) binding reinforcing steel bars of the newly cast foundation 9, erecting a template of the newly cast foundation 9, pouring concrete of the newly cast foundation 9, and pouring concrete of a part, lower than the top elevation of the newly cast foundation 9, of the bearing platform 1;
(8) after the concrete pile 2 is lowered to the proper position, a rubber block 3 is paved on the pile top;
(9) and after the house reaches three layers, the post-pouring hole 4 is sealed by the expanded concrete.
Example two
In this embodiment, for the foundation reinforced by the flexible pile such as the cement mixing pile 10, the following technical scheme is adopted:
the raft foundation is adopted as the foundation of the house after transformation, the thickness of the raft foundation is 700mm, the length of the cement mixing piles 10 is 15m, I-shaped steel 11 is inserted into part of the cement mixing piles 10, and the length of the I-shaped steel 11 is 30 m. The raft foundation is provided with a post-cast hole 4 at the arrangement part of the I-shaped steel 11, and the diameter of the post-cast hole 4 is the same as that of the cement mixing pile 10. And a rubber block 3 is laid on the I-shaped steel 11, and the thickness of the rubber block 3 is 180 mm. Set up the strengthening rib in 4 positions in back watering hole, the strengthening rib is 4 diameter for 25 mm's reinforcing bar, sets up the stirrup that the interval is 200mm simultaneously, and the stirrup diameter is 8 mm.
The number of the I-beams 11 is dually controlled according to the bearing capacity requirement and the settlement control requirement, the number of the I-beams 11 is preliminarily determined according to the bearing capacity, the number G of the I-beams 11 is determined according to the following formula, G is m2gAz/Ap2g，AzIs the area of the bottom of the raft foundation, m2gIs the replacement rate of I-shaped steel 11, namely the ratio of the total cross-sectional area of the pile to the bottom area of the raft foundation, Ap2gIs 11 sectional areas of the I-beams and 11 replacement rates m of the I-beams2gIs determined according to the following formula,
f＝m1sR1s/Ap1s+(Ec2g/Ec1s)m2gR2g/Ap2g+β(Es/Ec1s)fsin the formula m1sIs the replacement rate of the cement mixing pile 10 without the inserted I-beam 11, namely the ratio of the total cross section area of the cement mixing pile 10 without the inserted I-beam 11 to the bottom area of the raft foundation, R1sFor the bearing capacity of the cement mixing pile 10, Ap1sIs the cross section area of a cement mixing pile 10, Ec1sIs a cement mixing pile 10 modulus of elasticity, Ec2gIs the modulus of elasticity, m, of 11I-steel2gIs the I-steel 11 substitution rate, R2gBearing capacity of I-steel 11, Ap2gIs the sectional area of the I-shaped steel 11, the reduction coefficient of β is 0.75, EsIs the modulus of elasticity of the soil, fsThe bearing capacity of the soil foundation;
and (4) primarily determining the number of the I-beams 11 according to the bearing capacity requirement, and then performing settlement rechecking. The settlement calculation formula is as follows:where p is the stress transmitted from the upper part to the foundation, EsiIs the complex modulus, ziAnd Zi-1The depth of the basal bottom surface is respectively within the range of the bottom surface of the ith layer and the ith-1 layer,
and
the average additional stress coefficient from the bottom surface of the foundation to the bottom surfaces of the ith and (i-1) th layers is determined according to the technical Specification for treating building foundations (JGJ-79-91), the composite modulus of the whole foundation can be divided into three parts along the depth direction, the first part is the foundation formed by the cement mixing piles 10, the I-shaped steel 11 and the soil, the second part is the foundation formed by the I-shaped steel 11 and the soil, and the third part is the foundation formed by the soil of the lower lying layer. First part complex modulus Es1sThe calculation formula is as follows: es1s＝m1sEc1s+m2gEc2g+(1-m1s-m2g)EsSecond part composite modulus Es2sThe calculation formula is as follows: es2s＝m2gEc2g+(1-m2g)Es。
And if the settlement exceeds 100mm, increasing the length and the number of the I-beams 11 to perform re-settlement and rechecking until the settlement meets the requirement. According to the steps, the number of the I-beams 11 is determined to be 76.
The construction steps comprise:
(1) chiseling out a post-cast hole 4 of the raft plate concrete at the position where the I-shaped steel 11 is installed, and cutting off redundant steel bars on the upper part;
(2) a drilling machine drilling tool penetrates through the rear pouring hole 4 to drill an I-shaped groove in the pile body of the cement mixing pile 10, an I-shaped cutter is mounted at the head of the drilling machine to cut cement soil, a crane is adopted to hoist the I-shaped steel 11, and the perpendicularity is ensured by positioning a steel plate in the process that the I-shaped steel 11 is inserted into the I-shaped groove;
(3) and after the I-shaped steel 11 is inserted, water glass is injected to seal a gap between the I-shaped steel 11 and the I-shaped groove, and the injection pressure of the water glass is 1-1.2 MPa so as to ensure the grouting effect.
(4) Paving a rubber block 3 on the top of the I-shaped steel 11;
(5) after the house reaches three layers, placing a reinforcement cage consisting of reinforcing ribs and stirrups into the post-pouring hole 4;
(6) pouring a post-pouring hole 4, wherein the post-pouring hole 4 is made of expansive concrete; the pouring sequence of the post-pouring hole 4 is that the periphery is firstly poured and then the middle is poured, and a symmetrical sealing mode is adopted as much as possible.
Claims (1)
1. A foundation reinforcing construction method for building foundation is characterized in that the following technical scheme is adopted for a foundation reinforced by flexible piles such as cement mixing piles:
the method comprises the following steps that a raft foundation is adopted as a foundation of a house after transformation, the thickness of the raft foundation is 600-800 mm, I-shaped steel is inserted into part of cement mixing piles, and the length of the I-shaped steel is 1.8-2.5 times that of the cement mixing piles; a post-cast hole is arranged at the position where the I-shaped steel is arranged, and the diameter of the post-cast hole is the same as that of the cement mixing pile; paving a rubber block on the I-shaped steel, wherein the thickness of the rubber block is 150-200 mm; reinforcing ribs are arranged at the position of the post-cast hole, the reinforcing ribs are 4 reinforcing steel bars with the diameter of 25mm, and stirrups with the spacing of 200mm are arranged at the same time, and the diameter of each stirrup is 8 mm;
the construction steps comprise:
(1) chiseling out post-cast holes on raft concrete at the position where the I-shaped steel is installed, and cutting off redundant steel bars on the upper part;
(2) drilling an I-shaped groove in a cement mixing pile body by a drilling machine drilling tool through a rear pouring hole, mounting an I-shaped cutter at the head of the drilling machine to cut cement soil, hoisting an I-shaped steel by a crane, and ensuring the verticality by a positioning steel plate in the process of inserting the I-shaped steel into the I-shaped groove;
(3) after the I-shaped steel is inserted, water glass is injected to seal a gap between the I-shaped steel and the I-shaped groove, and the injection pressure of the water glass is 1-1.2 MPa so as to ensure the grouting effect;
(4) paving a rubber block on the top of the I-shaped steel;
(5) after the house reaches three layers, placing a reinforcement cage consisting of reinforcing ribs and stirrups into the post-pouring hole;
(6) pouring a post-pouring hole, wherein the post-pouring hole is made of expansive concrete; the pouring sequence of the post-pouring hole is that the periphery is firstly followed by the middle, and a symmetrical sealing mode is adopted;
for the foundation reinforced by rigid piles such as concrete piles, the following technical scheme is adopted: the method comprises the following steps of utilizing an original pile foundation and a concrete foundation to properly lower a bearing platform, adopting a raft foundation as a foundation of a modified house, wherein the thickness of the raft foundation is 600-800 mm, the raft foundation is composed of the lowered bearing platform and a new poured foundation, reinforcing steel bars with the diameter of 20-25 mm are adopted as lower reinforcing steel bars of the new poured foundation, the spacing between the reinforcing steel bars is 150-200 mm, the bearing platform and the new poured foundation are connected into a whole through connecting bars, the spacing between the connecting bars is 200-250 mm, the diameter of the connecting bars is 22-25 mm, the length of the connecting bars extending into pre-buried holes of the bearing platform is 250-300 mm, the diameter of the pre-buried holes of the bearing platform is 24-27 mm, gaps between the connecting bars and the pre-buried holes of the bearing platform are filled with epoxy resin, the connecting bars are exposed out of the length of the bearing platform to be 400-450 mm, post-poured holes;
arranging a small-diameter concrete pile outside a bearing platform, wherein the diameter of the small-diameter concrete pile is 150-300 mm, arranging a rubber block on the pile top of the concrete pile, the thickness of the rubber block is 100-150 mm, arranging a precast concrete pipe hoop on the pile head of the small-diameter concrete pile, the height of the precast concrete pipe hoop embedded into the pile head of the small-diameter concrete pile is 100mm, the top of the precast concrete pipe hoop is 120-150 mm higher than the pile top of the small-diameter concrete pile, paving a gravel sand cushion layer on the pile top of the small-diameter concrete pile, the thickness of the gravel sand cushion layer is 120-150 mm, the pile length of the small-diameter concrete pile is the same as that of the concrete pile, and the site geological condition is that a hard layer is arranged on a shallow part, the small-diameter concrete pile extends into the shallow hard layer for 500-800 mm, and forms a long and short pile structure with the concrete pile, the shallow hard layer is 10-20 m, and the deep hard layer into which the concrete pile extends is more than;
the number of the small-diameter concrete piles is controlled according to the requirements of bearing capacity and settlement control, the number of the small-diameter concrete piles is determined primarily according to the bearing capacity, the number S of the small-diameter concrete piles is determined according to the following formula, S is m2Az/Ap2, Az is the bottom area of a raft foundation, m2 is the replacement rate of the small-diameter concrete piles, namely the ratio of the total cross-sectional area of the piles to the bottom area of the raft foundation, Ap2 is the cross-sectional area of the small-diameter concrete piles, m2 is determined according to the following formula, f is m1R1/Ap1+ (Ec2/Ec1) m2R2/Ap2+ theta (Es/Ec1) fs, m1 is the replacement rate of the concrete piles in the formula, namely the ratio of the total cross-sectional area of the concrete piles to the bottom area of the raft foundation, R1 is the bearing capacity of the concrete, Ap1 is the cross-sectional area of the concrete piles, Ec1 is the modulus of the concrete piles, and the small-modulus of the concrete piles 2 is the modulus of the small-modulus of the, m2 is the replacement rate of the small-diameter concrete pile, R2 is the bearing capacity of the small-diameter concrete pile, Ap2 is the sectional area of the small-diameter concrete pile, theta is the reduction coefficient, 0.5-0.6 is taken, Es is the elastic modulus of soil, and fs is the bearing capacity of a soil foundation;
and (3) primarily determining the number of the small-diameter concrete piles according to the bearing capacity requirement, and then performing settlement rechecking, wherein the settlement calculation formula adopts the following steps:
wherein p is the stress transmitted to the foundation from the upper part, Esi is the composite modulus, Zi and Zi-1 are the depths from the bottom surface of the foundation to the bottom surfaces of the i-th layer and the i-1 st layer respectively, and the average additional stress coefficient from the bottom surface of the foundation to the bottom surfaces of the i-th layer and the i-1 st layer respectively, which are determined according to the technical Specification for treating building foundation (JGJ-79-91), the composite modulus of the whole foundation can be divided into three parts along the depth direction, the first part is the foundation formed by concrete piles, small-diameter concrete piles and soil, the second part is the foundation formed by concrete piles and soil, and the third part is the foundation formed by lower lying layer soil; the first part composite modulus Es1 calculation formula is as follows: es1 ═ m1Ec1+ m2Ec2+ (1-m1-m2) Es, and the second part complex modulus Es2 is calculated as follows: es2 ═ m1Ec1+ (1-m1) Es.
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| CN104912067A (en) * | 2014-03-15 | 2015-09-16 | 温州荣强海洋科技有限公司 | High-pressure rotary spraying threaded pile |
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