CN109024721A - A kind of underpinning and improve the method that ability is cut in the bending resistance of existing building rigid foundation - Google Patents
A kind of underpinning and improve the method that ability is cut in the bending resistance of existing building rigid foundation Download PDFInfo
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- CN109024721A CN109024721A CN201810807583.7A CN201810807583A CN109024721A CN 109024721 A CN109024721 A CN 109024721A CN 201810807583 A CN201810807583 A CN 201810807583A CN 109024721 A CN109024721 A CN 109024721A
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- 238000005452 bending Methods 0.000 title claims abstract description 26
- 238000000034 method Methods 0.000 title claims abstract description 10
- 238000009424 underpinning Methods 0.000 title abstract 2
- 239000011440 grout Substances 0.000 claims abstract description 40
- 230000002787 reinforcement Effects 0.000 claims abstract description 40
- 239000002689 soil Substances 0.000 claims abstract description 30
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 29
- 239000010959 steel Substances 0.000 claims abstract description 29
- 238000010276 construction Methods 0.000 claims abstract description 14
- 238000010008 shearing Methods 0.000 claims description 17
- 229910001294 Reinforcing steel Inorganic materials 0.000 claims description 13
- 238000005553 drilling Methods 0.000 claims description 7
- 238000002360 preparation method Methods 0.000 claims description 5
- 239000002985 plastic film Substances 0.000 claims description 4
- 229920006255 plastic film Polymers 0.000 claims description 4
- 238000007789 sealing Methods 0.000 claims description 3
- 238000004140 cleaning Methods 0.000 claims description 2
- 239000010779 crude oil Substances 0.000 claims description 2
- 238000007788 roughening Methods 0.000 claims description 2
- 230000003014 reinforcing effect Effects 0.000 abstract description 12
- 238000009435 building construction Methods 0.000 abstract description 2
- 238000005728 strengthening Methods 0.000 abstract 2
- 239000002002 slurry Substances 0.000 description 10
- 239000004568 cement Substances 0.000 description 7
- 230000007547 defect Effects 0.000 description 4
- 239000000463 material Substances 0.000 description 3
- 210000003205 muscle Anatomy 0.000 description 3
- -1 rubble Substances 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 239000004698 Polyethylene Substances 0.000 description 2
- 238000004873 anchoring Methods 0.000 description 2
- 238000009412 basement excavation Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 229920000573 polyethylene Polymers 0.000 description 2
- 230000000712 assembly Effects 0.000 description 1
- 238000000429 assembly Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 239000011449 brick Substances 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000005253 cladding Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000007667 floating Methods 0.000 description 1
- 238000009415 formwork Methods 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 238000007569 slipcasting Methods 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D37/00—Repair of damaged foundations or foundation structures
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Abstract
The invention discloses a kind of methods that underpinning and raising existing building rigid foundation bending resistance cut ability, it is related to technical field of building construction, its key points of the technical solution are that load-carrying members including original rigid foundation and thereon, the end reinforced of original rigid foundation is fixedly connected with transverse bar by grout sleeve level, the middle part of transverse bar is fixedly connected with vertical connecting rod vertically, and one end of transverse bar is connected with soil nailing by tensioning component；It is provided with steel reinforcement cage around original rigid foundation, transverse bar passes through steel reinforcement cage and is fixedly connected with steel reinforcement cage and integral by concreting, forms new spread foundation；Basis reinforcing scope according to strengthening of foundation or increase load upper back structure reach basic top surface vertical force design value and strengthening of foundation or increase load after act on the bottom of foundation torque design value determine.The present invention solves the problems, such as that rigid foundation can not be transformed into spread foundation by conventional construction method, is conducive to the bending resistance for improving existing rigid foundation building.
Description
Technical Field
The invention relates to the technical field of building construction, in particular to a method for reinforcing a foundation and improving the bending and shearing resistance of an existing building rigid foundation.
Background
Due to environmental influences, existing building foundation foundations need to be reinforced, such as construction adjacent to newly built buildings, deep foundation pit excavation, newly built underground engineering, natural disasters and the like. The main treatment methods for foundation pit reinforcement at present comprise foundation grouting reinforcement, foundation basal area increase and anchor rod static pressure piles.
The rigid foundation and the extended foundation are defined as follows in the national standard specification GB50007 'design Specification of building foundation foundations': the reinforcement-free extended foundation, which is called as a rigid foundation in the past, refers to an under-wall strip foundation or an under-column independent foundation which is composed of bricks, rubble, concrete or rubble concrete, affluent and Sanhe soil and the like. The rigid foundation has weak bending moment or shearing force resistance.
The expansion foundation refers to a foundation which expands the load transmitted by the upper structure into a certain bottom area towards the side edge, so that the compressive stress acting on the base is equal to or less than the allowable bearing capacity of the foundation soil, and the stress in the foundation simultaneously meets the strength requirement of the material. The bending and shearing resistance of the extended foundation can be designed according to the load requirements of the superstructure.
In the JGJ123 technical specification for reinforcing the foundation of the existing building foundation, aiming at the reinforcement of the existing building foundation, only the reinforcement when the bearing capacity of the existing building foundation is insufficient or the size of the bottom surface of the foundation does not meet the specification requirement is involved, and the force transmission mode of the foundation is not changed. The modified rigid foundation is still a rigid foundation, and the defect of weak bending moment resistance or shear force resistance still exists.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a reinforced foundation which can reinforce the rigid foundation of the existing building and simultaneously improve the bending shear resistance.
In order to achieve the purpose, the invention provides the following technical scheme: a reinforced foundation comprises an original rigid foundation and a bearing structure on the original rigid foundation, wherein the end part of a steel bar of the original rigid foundation is horizontally and fixedly connected with a transverse bar through a grouting sleeve, the middle part of the transverse bar is vertically and fixedly connected with a vertical pull rod anchored at the bottom of a foundation pit, and one end of the transverse bar, far away from the original rigid foundation, is connected with a soil nail fixed inside the side wall of the foundation pit through a tensioning assembly; a reinforcement cage is arranged around the original rigid foundation, and the transverse rib penetrates through the reinforcement cage, is fixedly connected with the reinforcement cage and is poured into a whole by concrete to form a new extended foundation with three dimensions of length, width and height of the original rigid foundation; the reinforcement range of the foundation is determined according to a design value of vertical force transmitted from the upper structure to the top surface of the foundation after the foundation is reinforced or the load is added, and a design value of moment acting on the bottom surface of the foundation after the foundation is reinforced or the load is added.
Through adopting above-mentioned technical scheme, new extension basis becomes whole through horizontal muscle and grout sleeve and original rigid foundation fixed connection for when consolidating the basis and receiving external acting force, original rigid foundation and new extension basis undertake jointly. The vertical pull rod is anchored at the bottom of the foundation pit, so that the bottom of the newly expanded foundation is connected with the ground into a whole, and the stability is improved. Because the end of the transverse bar is fixedly connected with the soil nail through the tensioning assembly, the side wall of the newly expanded foundation is connected with the foundation into a whole, and because the soil nail is positioned around the newly expanded foundation, the periphery of the newly expanded foundation is tensioned and fixed by the tensioning assemblies in different directions, so that the bending and shearing resistance is improved.
The invention is further configured to: the vertical pull rod is in an inverted U shape, the top of the vertical pull rod is pressed on the transverse rib, and barbs which are obliquely arranged upwards are arranged at two ends of the bottom of the vertical pull rod.
Through adopting above-mentioned technical scheme, horizontal muscle is fixed spacing by perpendicular pull rod, prevents that horizontal muscle from shifting up. On one hand, the barb increases the anchoring strength between the vertical pull rod and the bottom of the foundation pit, and prevents the vertical pull rod from being pulled out; on the other hand, the barb also increases the connecting strength of the vertical pull rod and concrete, increases the connecting stability of the newly expanded foundation and the ground, and improves the reinforcing effect.
The invention is further configured to: the tensioning assembly comprises a turnbuckle, one end of the turnbuckle is fixedly connected with the transverse bar through a steel wire rope, and the other end of the turnbuckle is fixedly connected with the soil nail through the steel wire rope.
By adopting the technical scheme, after the steel wire ropes at the two ends of the turnbuckle are fixed, the distance between the turnbuckle can be adjusted, so that the tensioning assembly is in a tensioning state and in operation.
The invention is further configured to: the soil nail comprises a prefabricated plug and coaxially fixed deformed steel bars, and an inflow pipe is arranged on the plug.
Through adopting above-mentioned technical scheme, after drilling on the foundation ditch lateral wall, put into the drilling with the deformed steel bar in, the drill way shutoff of drilling is connected to the end cap, and the slip casting machine of inflow pipe outside is connected, and in the thick liquid flowed into the drilling through the inflow pipe, because deformed steel bar and end cap coaxial fixed for the distance is the same basically around deformed steel bar and the drilling, and the cladding thickness is unanimous around the deformed steel bar after the thick liquid solidifies, improves soil nail's intensity.
The invention is further configured to: the grouting sleeve comprises a pipe body provided with a threaded through hole along the central axis, the middle part of the pipe body is thickened along the circumferential direction to form a convex ring, and a plurality of grout overflow holes communicated with the threaded through hole are formed in the convex ring along the circumferential direction; one end of the pipe body side wall is provided with a slurry inlet port communicated with the thread through hole, and the other end of the pipe body side wall is provided with a slurry outlet port communicated with the thread through hole.
By adopting the technical scheme, the convex ring increases the strength of the grouting sleeve, so that higher connection strength can be still maintained when the grouting hole is formed in the convex ring. The grout inlet of the grouting sleeve is connected with an external grouting machine through a pipeline, and the grout outlet of the grouting sleeve is blocked by a sealing head. In order to prevent the grout outlet from being blocked, a polyethylene film with the thickness of 0.03mm is wound and coated on the middle part of each grouting sleeve. After the concrete of the newly-expanded foundation is poured, high-pressure cement paste is injected into the grouting sleeve by using the grouting machine, the cement paste is filled in the threaded through hole of the grouting sleeve, and the end parts of the reinforcing steel bars and the transverse bars are coated, so that the reinforcing steel bars and the transverse bars are fixedly connected into a whole after the cement paste is solidified and hardened. In addition, in the grouting process, high-pressure slurry water breaks through the plastic film coated on the surface of the grouting sleeve through the slurry overflow hole, and the cement slurry enters a gap between the original rigid foundation and the new expansion foundation from the slurry overflow hole, so that the interface connection strength of the two is higher.
The invention is further configured to: when two adjacent grouting sleeves are connected, the grout outlet port of one grouting sleeve is connected with the grout inlet port of the other grouting sleeve through a grout pipe.
By adopting the technical scheme, during grouting, only the grouting interface of the first grouting sleeve needs to be grouted, and grout can enter the next grouting sleeve through the grout pipe without single grouting, so that the construction efficiency is improved.
Aiming at the defects in the prior art, the invention also aims to provide a construction method for improving the bending and shearing resistance of the existing building rigid foundation, which can reinforce the existing building rigid foundation and simultaneously improve the bending and shearing resistance.
In order to achieve the purpose, the invention provides the following technical scheme: a construction method for improving bending and shearing resistance of an existing building rigid foundation comprises the following steps:
s1: excavating a foundation pit around the original rigid foundation to expose the original rigid foundation, wherein the depth of the foundation pit is lower than the bottom elevation of the original foundation, and the size and the bearing capacity of the foundation to be expanded are designed;
s2: roughening and cleaning the interface of the original rigid foundation, exposing the reinforcing steel bars in the original rigid foundation, wherein the length of the exposed reinforcing steel bars is at least equal to one half of that of a grouting sleeve, sleeving the end parts of the reinforcing steel bars with the grouting sleeve, and sleeving the other end of the sleeve with a fixed transverse bar; two adjacent grouting sleeves are communicated through a grout pipe, a grout inlet interface of the first grouting sleeve is connected with an external grouting machine, and a grout outlet interface of the last grouting sleeve is blocked by a sealing head; the grout overflow hole in the middle of the grouting sleeve is wrapped by plastic film;
s3: binding and installing a reinforcement cage on the transverse bar, drilling a hole on the side wall of the foundation pit, fixing a soil nail which is obliquely arranged downwards, connecting the end part of the transverse bar with the end part of the soil nail by using a tensioning assembly, and adjusting to a tensioning state;
s4: performing anti-bending checking calculation, calculating the preparation quantity of the vertical pull rods, uniformly fixing the vertical pull rods in the middle of the transverse ribs, and implanting two ends of each vertical pull rod below the bottom surface of the foundation pit;
s5: the periphery of the reinforcement cage supports and fixes the template according to the size of the foundation to be expanded, and the end part of the transverse bar is exposed out of the foundation to be expanded; and pouring concrete, forming a new expansion foundation together with the reinforcement cage, the transverse ribs and the vertical pull rod, wherein the upper part of the new expansion foundation is wrapped at the root of the bearing structure to form a platform shape.
By adopting the technical scheme, the poured new expansion foundation and the original rigid foundation are integrated, the new expansion foundation is stably connected with the ground on the bottom surface and the periphery, and the reinforcing effect and the bending and shearing resistance are improved.
The invention is further configured to: the plane size of the foundation pit in the step S1 exceeds 80-100cm of each side of the length and the width of the designed reinforced foundation, and the design steps of the specification and the bearing capacity of the newly expanded foundation are as follows:
obtaining a bearing capacity characteristic value of a crude oil foundation according to design information of an existing building foundation, or directly determining an existing actual bearing capacity characteristic value of the foundation; investigating the design data of the existing building reinforcement and reconstruction, obtaining the design value of the vertical force transmitted from the upper structure to the top surface of the foundation after the foundation is reinforced or the load is increased, and the design value of the moment acting on the bottom surface of the foundation after the foundation is reinforced or the load is increased; according to the obtained F value, the M value and the obtained characteristic value of the bearing capacity of the foundation, estimating to obtain the length and the width of the reinforced foundation, checking the characteristic value of the bearing capacity of the foundation until the characteristic value is met, and obtaining the length and the width of the foundation to be reinforced; designing the height of the foundation, checking the shearing resistance, and checking the punched bearing capacity of the joint of the column and the foundation and the variable step of the foundation.
By adopting the technical scheme, the bearing capacity of the newly expanded foundation is checked, and the stability and the safety of the reinforced foundation are improved.
The invention is further configured to: in the step S5, the strength of the cast concrete is not lower than C20, and if the original foundation cracks or is damaged due to non-load reasons, a foundation reinforcement grouting reinforcement method is adopted for reinforcement.
By adopting the technical scheme, the newly expanded foundation has better strength, and the stability and the bending and shearing resistance are improved.
The invention is further configured to: in the step S4, the preparation number of the vertical pull rods is calculated and checked according to the bending resistance of the foundation in the standard GB50007 "design specification of foundation of building foundation".
By adopting the technical scheme, the single bearing capacity of the vertical pull rod cannot exceed the tensile strength value, and the service life is prolonged.
In summary, compared with the prior art, the invention has the following beneficial effects:
1. the invention overcomes the defect that the traditional construction method has high requirement on the original rigid foundation material, and solves the technical problem that the traditional construction method can not reform the rigid foundation into the extended foundation;
2. because the vertical pull rod, the tensioning assembly and the soil nail are adopted, the newly expanded foundation is more stably connected with the ground, the reinforcing effect is improved, and meanwhile, the bending resistance and shearing resistance of the original rigid foundation are improved;
3. the construction method has wide application range, has low requirement on the original rigid base material, is safe and reliable for the vertical pull rod, the tensioning assembly and the soil nail, is convenient for large-scale popularization, and can be widely applied to the construction of building reinforcement and reconstruction.
Drawings
FIG. 1 is a schematic view of an effect structure after cast concrete reinforcement;
FIG. 2 is a schematic view of an excavation range of a foundation pit according to the embodiment;
FIG. 3 is a schematic view of the connection structure of the original rigid foundation and the transverse bar;
FIG. 4 is a cross-sectional view highlighting the internal structure of the grout sleeve;
FIG. 5 is a schematic view of the structure of an expansion mechanism added to an original rigid foundation;
FIG. 6 is a schematic view of a structure of a soil nail fixed on the side wall of a foundation pit;
fig. 7 is a schematic diagram of a structure for installing a reinforcement cage and a vertical pull rod in a foundation pit.
Reference numerals: 1. a building; 11. original rigid foundation; 111. reinforcing steel bars; 12. a load bearing structure; 13. new and old foundation interface; 2. tamping a soil layer; 21. a foundation pit; 211. the side wall of the foundation pit; 3. a foundation reinforcement range; 4. an expansion mechanism; 41. transverse ribs; 42. grouting a sleeve; 421. a threaded through hole; 422. a slurry inlet interface; 423. a pulp outlet port; 424. a convex ring; 425. a slurry overflow hole; 5. soil nailing; 6. a reinforcement cage; 7. a vertical pull rod; 71. a barb; 8. a new extension basis; 9. a tension assembly.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings.
In which like parts are designated by like reference numerals. It should be noted that the terms "front," "back," "left," "right," "upper" and "lower" used in the following description refer to directions in the drawings, and the terms "bottom" and "top," "inner" and "outer" refer to directions toward and away from, respectively, the geometric center of a particular component.
Example (b): a reinforced foundation is shown in figure 1, and comprises an original rigid foundation 11 and a bearing structure 12, wherein the original rigid foundation 11 forms a building 1, a reinforcing steel bar 111 is arranged inside the original rigid foundation 11, the end part of the reinforcing steel bar 111 is fixedly connected with an expansion mechanism 4 positioned around the original rigid foundation 11, a vertical pull rod 7 vertically anchored in a ramming earth layer 2 is fixed on the expansion mechanism 4, a reinforcing cage 6 is arranged between the expansion mechanism 4 and the vertical pull rod 7, and the expansion mechanism 4, the vertical pull rod 7 and the reinforcing cage 6 are poured by concrete to form a new expansion foundation 8. Soil nails 5 which are arranged in a downward inclined mode are fixed on the outer side of the new expansion foundation 8 in the rammed soil layer 2, and the soil nails 5 are connected with the expansion mechanism 4 through a tensioning assembly 9.
The construction method of the reinforced foundation comprises the following steps:
(1) the design data of the original rigid foundation 11 of the existing building 1 are investigated to obtain design parameters including the length l ', the width b ', the height h ', the strength of the original rigid foundation 11 and the original upper load (the vertical force design value F ', the moment design value M ' acting on the bottom surface of the foundation) transmitted to the foundation.
(2) Investigating the original rigid foundation 11 design data of the existing building 1 to obtain the characteristic value (f) of the bearing capacity of the original rigid foundation 11a') or directly determining the characteristic value (f) of the existing actual bearing capacity of the foundationa)。
(3) The design data of the original rigid foundation 11 of the existing building 1 are investigated, and a vertical force design value (F) transmitted from the upper structure to the top surface of the foundation after the foundation is reinforced or the load is increased and a moment design value (M) acted on the bottom surface of the foundation after the foundation is reinforced or the load is increased are obtained.
(4) Designing the length l and the width b of the new extension foundation 8:
obtaining a characteristic value (f) of the bearing capacity of the foundation according to the existing technical Specification for reinforcing the foundation of the existing building (JGJ123) and the step (2)a) Firstly, estimating to obtain the length l and the width b of the new extension foundation 8;
when the axle center load acts:
p≤fa，
when the eccentric load acts, the following requirements are met besides the above formula:
pmax≤1.2fa，
wherein,
wherein f isaThe symbol obtained in step (2), F obtained in step (3), and M obtained in step (3) are shown in the existing technical Specification for foundation reinforcement of existing building foundations (JGJ 123).
(5) Designing the height of the new extension foundation 8 and performing shear checking calculation:
the shear checking calculation needs to check the punched bearing capacity of the joint of the column and the foundation and the variable-order position of the foundation, and the checking calculation formula is as follows:
Fl≤0.7βkp*ft*αm*h0，
αm＝(αt+αb)/2，
Fl＝pjAl，
in the above formula: h is0-a base effective height;
other symbols are detailed in the current design code of foundation of building foundation (GB 50007).
(6) Referring to fig. 2, the length l, width b and height h of the design according to the new extended base 80A foundation pit 21 is excavated around the original rigid foundation 11, and the depth of the foundation pit 21 is lower than the bottom elevation of the original rigid foundation 11, and is generally 10-30cm lower than the bottom of the original rigid foundation 11. The plane size of the foundation pit 21 exceeds 80cm-100cm on each side of the length and width of the foundation reinforcement range 3, and all the floating soil above the original rigid foundation 11 is excavated to expose the original rigid foundation 11.
(7) Referring to fig. 3, the outer periphery of the original rigid foundation 11 is a new and old foundation interface 13, the new and old foundation interface 13 is chiseled and brushed clean by a tool to expose the end of the steel bar 111 inside the original rigid foundation 11, a hole is expanded around the end of the steel bar 111, and the expansion mechanism 4 is installed at the end of the steel bar 111.
Referring to fig. 3 and 4, the expanding mechanism 4 includes a transverse bar 41 and a grouting sleeve 42, and the reinforcing bar 111 is fixedly connected to an end of the transverse bar 41 by the grouting sleeve 42. The transverse bar 41 can be deformed steel bar with the diameter of 30mm, and one end of the transverse bar 41, which is far away from the original rigid foundation 11, extends out of the boundary of the foundation reinforcement range 3 by 5-10 cm.
The grouting sleeve 42 comprises a pipe body provided with a threaded through hole 421 along the central axis direction, one end side wall of the pipe body is radially provided with a grout inlet 422 communicated with the threaded through hole 421, the other end side wall of the pipe body is radially provided with a grout outlet 423 communicated with the threaded through hole 421, the middle part of the pipe body is integrally formed along the circumferential direction of the pipe body with a convex ring 424, the convex ring 424 is radially provided with grout overflow holes 425 communicated with the threaded through hole 421 along the pipe body, the aperture of the grout overflow holes 425 can be 3-5mm, and the number of the grout overflow holes 425 can be 4 and are uniformly distributed.
The end of the reinforcing bar 111 and the end of the transverse bar 41 are inserted into the screw through-holes 421 from both ends of the grout sleeve 42, respectively. For grouting convenience, two adjacent grouting sleeves 42 may be connected in the following manner: the grout outlet 423 of one of the grouting sleeves 42 is connected with the grout inlet 422 of the other grouting sleeve 42 through a grout pipe. The grout inlet 422 of the first grouting sleeve 42 is connected to an external grouting machine through a pipeline, and the grout outlet 423 of the last grouting sleeve 42 is plugged. In order to prevent the grout holes 425 from being blocked, a polyethylene film with a thickness of 0.03mm is wound and coated on the middle portion of each grouting sleeve 42.
(8) Referring to fig. 5, a hole is drilled and a screw steel is implanted in the sidewall 211 of the foundation pit 21, a slurry is injected into the hole to form a soil nail 5 after the slurry is solidified, the soil nail 5 is obliquely arranged downwards, and the included angle between the soil nail 5 and the horizontal plane can be 15-30 degrees. And the exposed end part of the deformed steel bar is welded and fixed with a lifting ring. In order to facilitate the fixation and grouting of the deformed steel bar, a plug which is matched with the diameter of the drilled hole is fixedly sleeved at the end part of the deformed steel bar, and an inflow pipe can be arranged on the plug.
(9) Referring to fig. 6, a reinforcement cage 6 is bound and fixed in the foundation pit 21 in the region where the transverse bar 41 extends, and the joint between the reinforcement cage 6 and the transverse bar 41 may be wound and fixed by iron wires or welded and fixed. The middle part of the transverse bar 41 is vertically fixed with a vertical pull rod 7, the vertical pull rod 7 can be in an inverted U shape, the top end of the vertical pull rod 7 is pressed on the upper side of the transverse bar 41, and the bottom end of the vertical pull rod 7 is inserted into the ramming soil layer 2 below the foundation pit 21 for anchoring. In order to improve the fixing effect of the vertical pulling rod 7, a plurality of barbs 71 which are inclined upwards are fixed on the bottom end of the vertical pulling rod 7 along the height direction.
Before the vertical pull rod 7 is fixed, the preparation quantity of the vertical pull rod 7 is checked, and the bending resistance check calculation is carried out:
according to the F value and the M value obtained in the step (3) and the step (4), calculating and checking the bending resistance of the foundation according to the existing design standard of the foundation of the building foundation (GB50007), and obtaining the configuration quantity A of the vertical pull rods 75；
The area of the stressed steel bar of the vertical pull rod 7 can be determined according to the following formula:
wherein:
M—MIor MII；
fy is the design value of the tensile strength of the vertical pull rod,
according to A5And (5) reinforcing bars by numerical values.
(10) Referring to fig. 7, a layer of interface agent is coated on the interface 13 of the new and old foundations on the formwork supported at the periphery of the proposed new extension foundation 8, and concrete is poured for forming. And after the concrete is solidified and hardened to meet the design strength requirement, the template is disassembled. In order to improve the strength of the new extension foundation 8, the concrete strength is not lower than C20.
The end part of the transverse bar 41 is connected and fixed with the end part of the soil nail 5 by a tensioning assembly 9, the tensioning assembly 9 comprises a flange and a steel wire rope fixedly connected to the end connected with the flange, and the flange is adjusted to enable the steel wire rope to be in a tensioning state. The remaining space of the foundation pit 21 is filled with backfill.
(11) In order to improve the connection strength between the original rigid foundation 11 and the newly expanded foundation 8, high-pressure cement paste is injected into the grouting sleeve 42 by using a grouting machine, the cement paste is filled in the threaded through hole 421 of the grouting sleeve 42 and covers the end parts of the reinforcing steel bars 111 and the end parts of the transverse steel bars 41, and thus after the cement paste is solidified and hardened, the reinforcing steel bars 111 and the transverse steel bars 41 are fixedly connected into a whole.
In addition, in the grouting process, high-pressure grout breaks through the plastic film coated on the surface of the grouting sleeve 42 through the grout overflow holes 425, and the grout enters a gap between the original rigid foundation 11 and the new extension foundation 8 from the grout overflow holes 425, so that the interface connection strength of the two is higher.
The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments, and all technical solutions belonging to the idea of the present invention belong to the protection scope of the present invention. It should be noted that modifications and embellishments within the scope of the invention may occur to those skilled in the art without departing from the principle of the invention, and are considered to be within the scope of the invention.
Claims (10)
1. A reinforced foundation comprising an original rigid foundation (11) and a load-bearing structure (12) thereon, characterized in that: the end part of a steel bar (111) of the original rigid foundation (11) is horizontally and fixedly connected with a transverse bar (41) through a grouting sleeve (42), the middle part of the transverse bar (41) is vertically and fixedly connected with a vertical pull rod (7) anchored at the bottom of the foundation pit (21), and one end, far away from the original rigid foundation (11), of the transverse bar (41) is connected with a soil nail (5) fixed inside the side wall of the foundation pit (21) through a tensioning assembly (9); a reinforcement cage (6) is arranged around the original rigid foundation (11), and the transverse ribs (41) penetrate through the reinforcement cage (6), are fixedly connected with the reinforcement cage (6) and are poured into a whole by concrete to form a new expansion foundation (8) with three dimensions of length, width and height of the original rigid foundation (11); the reinforcement range of the foundation is determined according to a design value of vertical force transmitted from the upper structure to the top surface of the foundation after the foundation is reinforced or the load is added, and a design value of moment acting on the bottom surface of the foundation after the foundation is reinforced or the load is added.
2. The reinforced foundation of claim 1, wherein: the vertical pull rod (7) is in an inverted U shape, the top of the vertical pull rod (7) is pressed on the transverse rib (41), and two ends of the bottom of the vertical pull rod (7) are provided with barbs (71) which are obliquely arranged upwards.
3. The reinforced foundation of claim 2, wherein: the tensioning assembly (9) comprises a turnbuckle, one end of the turnbuckle is fixedly connected with the transverse bar (41) through a steel wire rope, and the other end of the turnbuckle is fixedly connected with the soil nail (5) through the steel wire rope.
4. The reinforced foundation of claim 1, wherein: the soil nail (5) comprises a prefabricated plug and coaxially fixed deformed steel bars, and an inflow pipe is arranged on the plug.
5. The reinforced foundation of claim 1, wherein: the grouting sleeve (42) comprises a pipe body provided with a threaded through hole (421) along the central axis, the middle part of the pipe body is thickened along the circumferential direction to form a convex ring (424), and a plurality of grout overflow holes (425) communicated with the threaded through hole (421) are formed in the convex ring (424) along the circumferential direction; one end of the side wall of the pipe body is provided with a pulp inlet port (422) communicated with the thread through hole (421), and the other end of the side wall of the pipe body is provided with a pulp outlet port (423) communicated with the thread through hole (421).
6. The reinforced foundation of claim 5, wherein: when two adjacent grouting sleeves (42) are connected, the grout outlet (423) of one grouting sleeve (42) is connected with the grout inlet (422) of the other grouting sleeve (42) through a grout pipe.
7. A construction method for improving the bending and shearing resistance of the existing building rigid foundation is characterized by comprising the following steps: the method comprises the following steps:
s1: excavating a foundation pit (21) around the original rigid foundation (11) to expose the original rigid foundation (11), wherein the depth of the foundation pit (21) is lower than the bottom elevation of the original foundation, and the size and the bearing capacity of the foundation to be expanded are designed;
s2: roughening and cleaning the interface of the original rigid foundation (11), exposing the reinforcing steel bars (111) in the original rigid foundation (11), wherein the length of the exposed reinforcing steel bars (111) is at least equal to one half of that of a grouting sleeve (42), sleeving the grouting sleeve (42) at the end part of each reinforcing steel bar (111), and sleeving a fixed transverse bar (41) at the other end of each sleeve; two adjacent grouting sleeves (42) are communicated by a grout pipe, a grout inlet interface (422) of the first grouting sleeve (42) is connected with an external grouting machine, and a grout outlet interface (423) of the last grouting sleeve (42) is blocked by a sealing head; the grout overflow hole (425) in the middle of the grouting sleeve (42) is wrapped by plastic film;
s3: binding and installing a reinforcement cage on the transverse bar (41), drilling a hole on the side wall of the foundation pit (21), fixing a soil nail (5) which is obliquely arranged downwards, connecting the end part of the transverse bar (41) with the end part of the soil nail (5) by using a tensioning assembly (9) and adjusting to a tensioning state;
s4: performing anti-bending checking calculation, calculating the preparation quantity of the vertical pull rods (7), uniformly fixing the vertical pull rods (7) in the middle of the transverse ribs (41), and implanting two ends of each vertical pull rod (7) below the bottom surface of the foundation pit (21);
s5: the periphery of the reinforcement cage (111) supports and fixes the template according to the size of the foundation to be expanded, and the end part of the transverse reinforcement (41) is exposed out of the foundation to be expanded; and pouring concrete, forming a new expansion foundation (8) together with the reinforcement cage (111), the transverse ribs (41) and the vertical pull rod (7), wherein the upper part of the new expansion foundation (8) is wrapped at the root part of the bearing structure (12) and is in a table shape.
8. The construction method for improving the bending and shearing resistance of the existing building rigid foundation according to claim 7, characterized in that: the plane size of the foundation pit (21) in the step S1 exceeds 80-100cm of each side of the designed length and width of the reinforced foundation, and the design steps of the specification and the bearing capacity of the newly expanded foundation (8) are as follows:
obtaining a bearing capacity characteristic value of a crude oil foundation according to design information of an existing building foundation, or directly determining an existing actual bearing capacity characteristic value of the foundation; investigating the design data of the existing building reinforcement and reconstruction, obtaining the design value of the vertical force transmitted from the upper structure to the top surface of the foundation after the foundation is reinforced or the load is increased, and the design value of the moment acting on the bottom surface of the foundation after the foundation is reinforced or the load is increased; according to the obtained F value, the M value and the obtained characteristic value of the bearing capacity of the foundation, estimating to obtain the length and the width of the reinforced foundation, checking the characteristic value of the bearing capacity of the foundation until the characteristic value is met, and obtaining the length and the width of the foundation to be reinforced; designing the height of the foundation, checking the shearing resistance, and checking the punched bearing capacity of the joint of the column and the foundation and the variable step of the foundation.
9. The construction method for improving the bending and shearing resistance of the existing building rigid foundation according to claim 7, characterized in that: in the step S5, the strength of the cast concrete is not lower than C20, and if the original foundation cracks or is damaged due to non-load reasons, a foundation reinforcement grouting reinforcement method is adopted for reinforcement.
10. The construction method for improving the bending and shearing resistance of the existing building rigid foundation according to claim 7, characterized in that: in the step S4, the preparation number of the vertical pull rods (7) is calculated and checked according to the bending resistance of the foundation in the standard GB50007 "design code of building foundation".
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