CN113846714B

CN113846714B - Method for repairing and reinforcing raft foundation

Info

Publication number: CN113846714B
Application number: CN202111147021.2A
Authority: CN
Inventors: 李庆涛; 夏浩然; 刘普; 陈建设; 柴英鹏; 屈路阳; 刘萌; 朱明权; 王浩; 徐成; 袁广林; 黄晨
Original assignee: China University of Mining and Technology CUMT
Current assignee: China University of Mining and Technology CUMT
Priority date: 2021-09-28
Filing date: 2021-09-28
Publication date: 2022-05-06
Anticipated expiration: 2041-09-28
Also published as: CN113846714A

Abstract

A method for repairing and reinforcing raft foundations is characterized in that steel pipes and jacks are used for supporting frame beams around frame columns; supporting the frame column by using a steel frame, a steel corbel and a jack; arranging a laser range finder on the ground around the frame column; slowly pressing each jack to enable the frame column and the frame beam to synchronously rise to a set height; arranging a plurality of grouting holes on an original raft foundation below the frame columns, and respectively performing grouting operation in a settlement crack inside the original raft foundation and in a suspension space of a foundation bottom plate; carrying out bar planting and steel bar binding operation on the original raft foundation; heightening an original raft foundation to form a raft heightening part; repairing the raft foundation and the frame beam; curing the poured concrete; and the jack unloads and removes the steel pipe, the steel frame and the steel bracket. The method can solve the problem of settlement damage of raft foundation caused by overload, and can ensure that the repaired and reinforced raft foundation has good bearing capacity and stable service life.

Description

Method for repairing and reinforcing raft foundation

Technical Field

The invention belongs to the technical field of building reinforcement, and particularly relates to a method for repairing and reinforcing a raft foundation.

Background

High-rise buildings and super high-rise buildings are produced while the technological level is rapidly developed and the construction land is increasingly reduced. However, in the high-rise building construction and the reconstruction and reinforcement, the foundation design occupies an important position in the whole high-rise building design. Raft foundations are widely used because of their advantages of good integrity, high bending rigidity, resistance to uneven loads of the superstructure and uneven settlement of the foundation, etc. The foundation is used as a part of a building structure and bears all loads transmitted by an upper structure, and the safety of the building is directly influenced by the quality of the design of the foundation. The method has higher and higher requirements on the foundation design of the building, but the problems of design errors, construction defects and the like are inevitable in the foundation design process. On the other hand, irreversible damage to the structure due to improper use or functional change of the building, damage to the foundation due to natural disasters, and the need for repairing the foundation itself are also sometimes encountered. The above problems cause the threat of life and property safety to owners and bring great economic loss and harm to the country. Therefore, in recent years, the construction focus of each country is gradually shifted to the aspects of maintenance, modification and reinforcement of the existing building, and the protection and reinforcement of the building are more and more emphasized.

The foundation is an important component of the building and is also the most concealed and difficult to reform. The quality problem of the foundation is often reflected by certain changes of the upper structure and is difficult to be directly discovered, and the quality of the foundation is directly related to the safety and the service performance of the building. For the reconstruction and reinforcement of the existing building, the principles of safety, applicability and economy are required from design to construction. Therefore, whether in the construction stage or in the delivered use, if the construction stage or the delivered use is removed and rebuilt, the construction cost is greatly increased, and meanwhile, the normal use process of the residents is seriously influenced. In consideration of the particularity of the foundation position of the building, the complexity degree is high, the difficulty is high in the transformation process, and the construction can be carried out only by making a detailed design and technical construction scheme. Therefore, it is necessary to research a method for improving and reinforcing foundation damage caused by incomplete design, construction defects, misuse, exceeding design service life and the like, which has short operation period, quick response and relatively simple construction process.

Because the building foundation is in a hidden position, the damage factor is difficult to directly judge, and the reconstruction is also very difficult. The method brings great challenges to the research work of foundation reinforcement and reconstruction, which is also the reason why the existing building foundation reinforcement is widely regarded by people all the time. In conclusion, the development of the raft foundation transformation and reinforcement method has important significance in realizing the foundation transformation and reinforcement design of the building and meeting the requirement of retaining the original design standard of the building.

Disclosure of Invention

Aiming at some problems in the prior art, the invention provides a method for repairing and reinforcing a raft foundation, which has the advantages of short operation period, quick effect, simple construction process, capability of solving the problem of overload settlement damage of the raft foundation, capability of ensuring that the reinforced raft foundation has good bearing capacity and stable service life, and capability of effectively meeting the requirements of the use function and the building safety level of the raft foundation.

In order to achieve the purpose, the invention provides a method for repairing and reinforcing a raft foundation, which comprises the following steps:

jacking and supporting frame beams around a frame column above an overload settlement damage position;

selecting a supporting position which ensures that the frame column can rise and the frame beam and the bottom plate cannot be damaged secondarily; arranging vertical steel pipes below the supporting positions of the two sides of the frame column on each frame beam, enabling the upper ends of the steel pipes to be supported on the lower end surfaces of the frame beams, and installing jacks between the lower ends of the steel pipes and the ground;

two steel brackets are fixedly connected to the opposite two sides of the middle part or the upper part of the frame column, two steel frames are arranged below the two steel brackets, and each steel frame consists of a steel frame beam horizontally arranged below the frame beam and two vertical steel frame columns fixedly connected below the two ends of the steel frame beam; the lower ends of the steel frame columns in the two steel frames are abutted to the ground, and the upper ends of the steel frame beams are connected with the lower ends of the corresponding steel corbels through jacks;

step two, erecting a monitoring instrument;

arranging a plurality of laser range finders on the ground around the frame column, wherein the laser range finders are used for monitoring the rising height of the frame column and the deflection of the frame beam in the jacking process;

step three, jacking up the frame column;

jacking the frame columns by using the steel brackets, the steel frames and the jacks, and jacking the frame beams around the corresponding frame columns by using the steel pipes and the jacks synchronously; slowly pressing a jack at the upper end of the steel frame beam and a jack at the lower end of the steel tube, so that the frame columns are lifted to a set height, ensuring that each frame beam on the periphery reaches a horizontal state, synchronously driving the raft foundation subjected to settlement damage to lift towards the upper part in the lifting process of the frame columns, and forming a foundation bottom plate suspension space between the raft foundation subjected to settlement damage and the foundation;

in the process, the rising height of the frame column is recorded through a laser range finder; after jacking, locking each jack;

step four, forming a grouting hole A and a grouting hole B;

an inner side grouting area is selected at the central part of a raft plate foundation which is subjected to settlement damage below a frame column, and an outer side grouting area is selected at the peripheral part; a plurality of grouting holes A are formed in the inner grouting area in a mode of surrounding the frame columns, the lower ends of the grouting holes A are stopped inside the raft foundation subjected to settlement damage, and the grouting holes A are communicated with settlement cracks generated on the raft foundation subjected to settlement damage; a plurality of grouting holes B are formed in the outer grouting area around the frame columns, and the lower ends of the grouting holes B sequentially and vertically penetrate through the lower part of the raft foundation and the foundation which are subjected to settlement damage;

step six, grouting operation;

inserting grouting steel pipes B into the grouting holes B, sequentially filling the part below the raft foundation subjected to settlement damage through compaction grouting of the grouting steel pipes B, filling the suspended space of the foundation slab, forming cement soil by combining cement slurry and the soil, enhancing the bearing capacity of the foundation, and reconnecting the raft foundation subjected to overload settlement damage and the original raft foundation into a whole; inserting a grouting steel pipe A into the grouting hole A, and grouting settlement cracks in the raft plate foundation subjected to settlement damage by using the grouting steel pipe A so as to enhance the safety and stability of the raft plate foundation subjected to overload settlement damage;

step seven, planting bars and binding the bars;

selecting a drilling position on the raft foundation, and performing drilling operation; selecting a drilling position on the raft foundation, and performing drilling operation; then, planting a lacing wire and a longitudinal rib in the drilled hole; then binding the implanted lacing wire and the longitudinal bar;

step eight, repairing the raft foundation and the beam section;

erecting a heightening template at the upper end of the raft foundation, erecting a repairing template at the periphery of the cracking part on the frame beam, then pouring concrete above the original raft foundation by using the heightening template to form a raft foundation heightening part, and pouring concrete at the periphery of the cracking part on the frame beam by using the repairing template to form a repairing surface;

step nine, concrete curing;

curing the poured concrete;

step ten, unloading and removing the steel pipes, the steel corbels and the steel frame by using the jack;

and D, after the grouting material in the step nine reaches the design strength, slowly lowering the jack, monitoring the settlement condition of each frame column through a laser range finder, stopping the lowering of the jack if the frame column is greatly settled, and performing rework treatment on the steps seven to nine until no abnormal deformation condition occurs in the process of lowering the jack, namely removing the steel pipe, the steel corbel and the steel frame, removing the jack, and removing the laser range finder.

Further, in order to guarantee the high strength of being connected of steel corbel and frame post, in step one, the frame post has been seted up in the position that corresponds steel corbel inner end fixed plate and has been held the recess, and the fixed plate of steel corbel inner end inlays to be established in holding the recess, and the steel corbel is through running through the chemical crab-bolt fixed connection who passes through the fixed plate in the outside of frame post.

Further, in order to ensure stability in the supporting process, in the first step, the steel pipe is a square steel pipe column with a square cross section.

Further, in order to ensure the stability of the fixing position of the steel corbel in the process of jacking the frame column, the accommodating groove is matched with the fixing plate, the depth of the accommodating groove is preferably 50mm, and 8 bolt holes with the diameter of 22mm are circumferentially and uniformly formed in the edge part of the fixing plate; the model number of the chemical anchor bolt is M20.

Further, in order to effectively ensure the bearing capacity of the reinforced independent foundation and ensure the engineering quality after reinforcement, in the sixth step, in the process of filling the suspended space of the foundation slab, grouting holes B communicated with the suspended space of the foundation slab are added on the basis of the raft slab which is damaged by settlement according to the on-site soil body grouting situation for re-grouting until each grouting point can not continue to be grouted.

Further, in order to ensure that the reinforced part can satisfy the load-bearing strength, in step seven, the implanted lacing wire is

The longitudinal ribs are implanted

Further, in order to ensure that the implanted steel bars can be firmly fixed in the drilled holes through the structural adhesive, in the seventh step, before the steel bars are implanted into the drilled holes, brushing the walls of the drilled holes with steel wire brushes, and extending dust in the holes into the holes by an air pump to blow the dust completely; simultaneously, removing rust on the bonding surface of the steel bar by using a hand grinding wheel until the metallic luster is exposed; and then, wiping the dust on the surface of the steel bar by using cotton yarn dipped in acetone.

And further, in order to ensure that the strength of the mixed loading soil after pouring can meet the design requirement, in the step eight, the concrete is selected from high-strength non-shrinkage grouting material.

In the transformation and reinforcement method provided by the invention, the jack and the steel pipe are used for supporting the frame beams around the frame column, and meanwhile, the steel frame, the steel corbel and the jack are matched for supporting the frame column, so that the frame column and the frame beams around the frame column can be stably supported; in addition, the steel frame is an integral structure consisting of a steel frame beam and two steel frame columns, so that a more stable supporting structure can be provided; the frame column jacking mechanism formed by the steel bracket, the steel frame and the jack can stably and reliably jack the frame column. The frame beam jacking mechanism formed by the steel pipes and the jacks can stably and reliably jack the frame beams around the frame columns. The raft foundation damaged by settlement can be lifted through synchronous jacking operation of the frame column jacking mechanism and the frame beam jacking mechanism, so that the problem of overload settlement damage of the raft foundation can be effectively solved; in the repairing and reinforcing process, the jacking conditions of the frame columns and the frame beams are monitored in real time by using a laser range finder, so that the lifting heights of the frame columns and the frame beams in the jacking process can be timely and conveniently mastered, and the frame columns and the frame beams can be ensured to be in a smooth state at last, so that the subsequent modification link can be safely and reliably carried out, and meanwhile, the requirement of maintaining the stability of the foundation during the subsequent grouting and steel bar recovery is effectively ensured; after jacking is finished, the jack is locked when all the frame columns above the building are ensured to be positioned at the same height position after settlement damage occurs, so that the building can be stably and reliably supported after jacking, and the safe operation of the subsequent operation process can be ensured; the central part of the raft foundation is provided with the grouting hole A communicated with the settlement crack, so that grouting can be conveniently carried out in the settlement crack, the interior of the raft foundation subjected to settlement damage can be repaired by grouting, the bearing strength and the integral stability of the raft foundation subjected to settlement damage can be effectively improved, the peripheral part of the raft foundation subjected to settlement damage is provided with the grouting hole B communicated with the lower part of the foundation, not only can the part below the foundation be conveniently grouted, but also the suspended space of the foundation bottom plate formed between the lifted raft foundation and the foundation can be grouted, so that the part below the foundation, the lifted raft foundation subjected to settlement damage and the original raft foundation can be reconnected into a firm whole by grouting, the sufficient reinforcement effect is achieved, and meanwhile, the bearing capacity of the raft foundation subjected to repair and reinforcement is effectively guaranteed, the construction method ensures that the repaired and reinforced building meets the requirement of the construction safety level. The regional setting of inboard slip casting communicates the not grouting holes A that runs through the thickness direction of inside settlement crack, and set up in the regional setting of slip casting in the outside and communicate the grouting holes B that runs through the thickness direction of former independent basis below, not only can quick effectual the settlement crack that produces raft foundation restore the reinforced purpose, can also effectively realize fast and consolidate the purpose of support to the raft foundation after raising, thereby can realize the dual purpose of restoreing the reinforcement to raft foundation inside and raft foundation below under the condition that destroys the minimum to raft foundation. The original independent foundation is heightened after bar planting and binding, and the bearing capacity and the stability of the post lower raft foundation after reinforcement and transformation can be further improved. The method has the advantages that the bearing capacity and stability of the frame beams around the frame column can be improved by repairing the cracking position on the frame beam, and further the load of the frame column can be effectively shared. Like this, through strengthening and carrying out reinforced (rfd) dual reinforcement mode to taking place to subside the raft board basis of destruction and strengthening to the frame roof beam and promoted the holistic stability of building, ensured the building security level of restoreing the building after consolidating. The method enhances the bearing capacity of the settlement failure part of the column lower raft foundation, effectively ensures that the repaired and reinforced column lower raft foundation has stable and reliable bearing capacity, and ensures the building safety level and the service life of the modified building; the method can solve the problems of foundation settlement damage and uneven settlement caused by the fact that the thickness of the top plate of the foundation is over-limit, can ensure that the reinforced and transformed lower raft foundation has good bearing capacity and stable service life, and meets the requirements of the use function of the lower raft foundation and the building safety level.

Drawings

Fig. 1 is a schematic plan structure view of a reinforced raft foundation to be repaired in the invention;

FIG. 2 is a cross-sectional view taken along line A-A of FIG. 1;

FIG. 3 is a schematic view of the assembly of the steel corbel and frame post of FIG. 2;

FIG. 4 is a cross-sectional view taken along line B-B of FIG. 1;

fig. 5 is a schematic structural view of the original raft foundation under the column in the invention when not being modified and heightened;

fig. 6 is a schematic structural view of the original raft foundation under the column of the invention after being transformed and heightened;

fig. 7 is a schematic structural view of bar planting on a raft foundation in the present invention.

In the figure: 1. raft foundation, 2, foundation, 3, settlement crack, 4, grouting steel pipe A, 5, grouting steel pipe B, 6, frame column, 7, frame beam, 8, steel frame beam, 9, steel frame column, 10, fixing plate, 11, steel corbel, 12, jack, 13, steel base plate, 14, steel pipe, 15, laser range finder, 16, foundation subsidence space, 17-1, grouting hole A, 17-2, grouting hole B, 18, heightening part of raft foundation, 19, lacing bar, 20 and longitudinal bar.

Detailed Description

The present invention is further described below.

As shown in fig. 1 to 7, a method for repairing and reinforcing a raft foundation includes the following steps:

step one, jacking and supporting frame beams 7 around a frame column 6 above an overload settlement damage position;

selecting a supporting position which ensures that the frame column 6 can rise and the frame beam 7 and the bottom plate cannot be damaged secondarily; arranging vertical steel pipes 14 below the supporting positions of the two sides of the frame column 6 on each frame beam 7, enabling the upper ends of the steel pipes 14 to be supported on the lower end face of the frame beam 7, and installing a jack 12 between the lower end of each steel pipe 14 and the ground;

two steel brackets 11 are fixedly connected to the opposite two sides of the middle part or the upper part of the frame column 6, two steel frames are arranged below the two steel brackets 11, and each steel frame consists of a steel frame beam 8 horizontally arranged below the frame beam 7 and two vertical steel frame columns 9 fixedly connected below the two ends of the steel frame beam 8; the lower ends of the steel frame columns 9 in the two steel frames are abutted to the ground, and the upper ends of the steel frame beams 8 are connected with the lower ends of the corresponding steel corbels 11 through jacks 12; as a preferred, the base is installed to the lower extreme of steel frame post 9, the base adopts rag bolt and ground fixed connection to increase the stability and the reliability that steel frame supported, thereby can ensure better that 6 jacking operations of frame post can safe and reliable go on.

For effectual assurance joint strength, the frame post 6 has been seted up in the position that corresponds 11 inner end fixed plates 10 of steel corbel and has been held the recess, and the fixed plate 10 of 11 inner ends of steel corbel inlays and establishes in holding the recess, and steel corbel 11 is through running through the chemical crab-bolt fixed connection of fixed plate 10 in the outside of frame post 6. In order to ensure the stability of the fixed position of the steel corbel in the process of jacking the frame column, the accommodating groove is matched with the fixing plate, the depth of the accommodating groove is preferably 50mm, and 8 bolt holes with the diameter of 22mm are circumferentially and uniformly formed in the edge part of the fixing plate; the model number of the chemical anchor bolt is M20.

In order to ensure the smoothness of contact and protect the local part of the original building from being damaged in jacking, a steel backing plate 13 is paved between the bottom of each jack 12 and the ground, and the steel backing plate 13 is paved between each steel pipe 14 and the frame beam 7; and a steel backing plate 13 is paved between the lower end of each steel frame column 9 and the ground, and the steel backing plate 13 is paved between the bottom of the jack 12 and the steel frame beam 9.

In order to ensure the stability of the support and at the same time to ensure sufficient load-bearing capacity during the jacking, two steel pipes 14 and two 50 ton jacks 12 are provided at the support positions on each side of the frame beam 7 for support. As a further preference, during the supporting process, the smooth contact between the steel tube 14 and the frame beam 7 through the steel backing plate 13 is ensured;

preferably, the steel pipe 14 is a square steel pipe column having a square cross section, and preferably has a size of 200mm × 200mm and a wall thickness of 5 mm.

Step two, erecting a monitoring instrument;

arranging a plurality of laser distance meters 15 around the frame column 6 on the ground for monitoring the rising height of the frame column 6 and the deflection of the frame beam 7 in the jacking process;

step three, jacking up the frame column 6;

jacking the frame column 6 by using the steel bracket 11, the steel frame and the jack 12, and jacking the frame beam 7 corresponding to the periphery of the frame column 6 by using the steel pipe 14 and the jack 12 synchronously; slowly pressing a jack 12 at the upper end of a steel frame beam 8 and a jack 12 at the lower end of a steel pipe 14 to enable the frame column 6 to rise to a set height and ensure that each frame beam 7 on the periphery reaches a horizontal state, synchronously driving the raft foundation 1 subjected to settlement damage to rise to the upper part in the process of rising the frame column 6, and forming a foundation slab suspension space between the raft foundation 1 subjected to settlement damage and the foundation 2;

in this process, the rising height of the frame post 6 is recorded by the laser range finder 15; after the jacking is finished, locking each jack 12;

in order to ensure the stable operation of the jacking process and the safety of the operation process, after the jack 12 presses 5 times, whether the frame column 6 ascends or not is checked, whether the surfaces of the frame beam 7 and the frame column 6 crack or not is observed, and the reciprocating operation is carried out until the ascending height of the frame column 6 reaches a set height and the two sides of each frame beam 7 around the frame column are in a horizontal state.

Step four, forming a grouting hole A and a grouting hole B;

an inner side grouting area is selected at the central part of the raft plate foundation 1 which is subjected to sedimentation damage below the frame column 6, and an outer side grouting area is selected at the peripheral part; a plurality of grouting holes A17-1 are formed in the inner grouting area around the frame column 6, the lower ends of the grouting holes A17-1 are stopped inside the raft foundation 1 subjected to settlement damage, and the grouting holes are communicated with settlement cracks 3 generated in the raft foundation 1 subjected to settlement damage; a plurality of grouting holes B17-2 are formed in the outer grouting area around the frame column 6, and the lower ends of the grouting holes B17-2 sequentially and vertically penetrate through the foundation 2 and the lower part of the raft foundation 1 subjected to settlement damage;

in order to ensure that a plurality of frame columns can be stably and orderly jacked to ensure the controllability of a jacking process, if a plurality of frame columns 6 are provided, after jacking support treatment in the step one is carried out one by one, jacks 12 around each frame column 6 are sequentially and slowly pressed to jack each frame column 6, each frame column 6 is jacked, marks are made in the jacking process, the settlement condition of each side of each frame column 6 is recorded and observed at any time, jacking is not carried out if one side is horizontal, then the other side is jacked to be in a horizontal state until the jacking height of the other side reaches a set height, and both sides are in a horizontal state.

Step six, grouting operation;

inserting grouting steel pipes B5 into the grouting holes B17-2, sequentially filling the part below the raft foundation 1 which is subjected to settlement damage through the grouting steel pipes B5 in a compacting grouting manner, filling the suspended space of the foundation slab, combining cement paste and soil to form cement soil, enhancing the bearing capacity of the foundation 2, and reconnecting the raft foundation 1 which is subjected to overload settlement damage and the original raft foundation 1 into a whole; in the process, the grouting steel pipe B5 is firstly inserted below the foundation 2, after the part below the foundation 2 is completely filled, the grouting steel pipe B5 is lifted, the lower end of the grouting steel pipe is stopped in the suspension space of the foundation slab, and then the suspension space of the foundation slab is fully filled; a grouting steel pipe A4 is inserted into the grouting hole A17-1, and the grouting steel pipe A4 is used for grouting settlement cracks 3 in the raft plate foundation 1 which is damaged by settlement, so that the safety and stability of the raft plate foundation 1 which is damaged by overload settlement are enhanced;

in order to effectively ensure the bearing capacity of the reinforced independent foundation and ensure the engineering quality after reinforcement, grouting holes B17-2 communicated with the suspended space of the foundation slab are added on the raft foundation 1 damaged by settlement according to the field soil mass grouting condition for re-grouting in the process of filling the suspended space of the foundation slab until each grouting point can not continue to feed slurry. Preferably, during the grouting process, attention is paid to protect underground pipe networks and cables, and whether the drainage well enters the cement paste or not is observed.

Step seven, planting bars and binding the bars;

selecting a drilling position on the raft foundation 1, and performing drilling operation; according to the design requirement, paying off is carried out to obtain a drilling position, drilling is carried out at the design position through an electric hammer, the aperture of the drilling hole is 4-6 mm larger than the diameter of the steel bar to be implanted, and the depth of the drilling hole is not smaller than the diameter of the steel bar to be implanted by 20 d. MakingPreferably, the tie bars 19 in the raft foundation 1 are

The longitudinal ribs 20 are

Filling special structural adhesive upwards from the bottom of the drilled hole, wherein the filling height is 2/3 of the depth of the drilled hole, and then implanting the lacing wires 19 and the longitudinal ribs 20 until the structural adhesive is solidified; then the implanted lacing wires 19 and the longitudinal ribs 20 are bound;

in order to ensure that the implanted steel bars can be firmly fixed in the drilled hole through structural adhesive, before the steel bars are implanted into the drilled hole, brushing the wall of the drilled hole with a steel wire brush, and extending dust in the hole into the hole with an air pump to blow the dust completely; simultaneously, removing rust on the bonding surface of the steel bar by using a hand grinding wheel until the metallic luster is exposed; and then, wiping the dust on the surface of the steel bar by using cotton yarn dipped in acetone. Through the brush hair processing to the pore wall, to the cleaning process of downthehole, to the rust cleaning and the dust removal processing on reinforcing bar surface, can be favorable to the structure glue more stable with reinforcing bar and pore wall bonding to can effectually ensure the firm stability of bar planting.

Preferably, the depth of the bar planting on the top of the original raft foundation 1 should not exceed 4/5 of the thickness of the original raft foundation 1.

Preferably, the drawing is familiar before the steel bars are bound, the batching tables and the batching boards of the steel bars are checked, the diameters, the shapes, the sizes and the number of the steel bars are checked, and if errors and omissions exist, the correction and the supplement are carried out; meanwhile, preparing iron wires, binding tools and the like for binding; during binding, the binding difficulty is reduced by paying attention to the sequence matched with other specialties such as templates and the like, joints of stirrups are required to be staggered on reinforcing steel bars at four corners, and crossed points of inserted bar corners and longitudinal reinforcing steel bars are required to be firmly fastened to prevent the framework from being inclined. The steel bars need to be horizontally and vertically bound, and the space between the steel bars is uniform.

Step eight, repairing the raft foundation 1 and the beam section;

erecting a heightening template at the upper end of the raft foundation 1, erecting a repairing template at the periphery of the cracking part on the frame beam 7, then pouring concrete above the original raft foundation 1 by using the heightening template to form a raft foundation heightening part 18, and pouring concrete at the periphery of the cracking part on the frame beam 7 by using the repairing template to form a repairing surface;

fig. 5 shows a schematic structural diagram of an original raft foundation under a column without being transformed and heightened, wherein a foundation sinking space 16 exists, fig. 6 shows a schematic structural diagram of the original raft foundation under the column after being transformed and heightened, the foundation sinking space 16 is eliminated, a foundation heightened part 18 is formed through heightening and transformation, and the bearing capacity of the raft foundation 1 under the frame column 6 is effectively improved.

Preferably, the concrete is selected from high-strength non-shrinkage grouting material, a ratio test of water and the grouting material is carried out before pouring, and the water cement ratio is preferably 0.15; meanwhile, the insertion type vibrator is utilized to vibrate in a fast insertion and slow pulling mode, the vibrating insertion points are uniformly arranged and move point by point, the vibration is performed sequentially, and the vibration is uniform and cannot be omitted. The moving distance is not more than 1.5 times of the action radius of the vibrating rod, and is generally 30-40 cm. When the upper layer is vibrated, the lower layer is inserted by 50mm to eliminate the joint between the two layers. The pouring process is carried out continuously, if the interval exists, joints are needed before the initial setting of the concrete, the joint is generally not more than 2 hours, otherwise, the joints are needed to be processed according to construction joints. When the slump of the concrete is more than 15cm, vibrating once; when the slump is less than 15cm, mechanical vibration is mainly used, manual tamping is used as an auxiliary, and the tamping time is preferably 15-30 s. In the concrete pouring process, the steel bars cannot be moved at will, and the accuracy of checking the thickness of the steel bar protective layer and the firmness and position of the embedded part is often enhanced, so that the strength of the concrete reaches C40 and above.

Step nine, concrete curing;

curing the poured concrete;

preferably, the concrete surface is maintained by spraying water with a sprayer, and the sprayer is responsible for a special person to continuously spray water for several times a day after the concrete surface is dried. Ensure that the later strength is greatly improved.

Step ten, unloading and removing the steel pipe 14, the steel corbel 11 and the steel frame by using the jack 12;

and after the grouting material in the step nine reaches the design strength, slowly lowering the jack 12, monitoring the settlement condition of each frame column 6 through the laser range finder 15, stopping the lowering of the jack 12 if the frame column 6 has large settlement, and performing rework treatment on the steps seven to nine until no abnormal deformation condition occurs in the process of lowering the jack 12, namely removing the steel pipe 14, the steel corbel 11 and the steel frame, removing the jack 12 and removing the laser range finder 15.

Claims

1. A method for repairing and reinforcing a raft foundation is characterized by comprising the following steps:

jacking and supporting frame beams (7) around a frame column (6) above an overload settlement damage position;

selecting a supporting position which ensures that the frame column (6) can rise and the frame beam (7) and the bottom plate cannot be damaged secondarily; arranging vertical steel pipes (14) below supporting positions, which are positioned at two sides of the frame column (6), on each frame beam (7), supporting the upper ends of the steel pipes (14) on the lower end surface of the frame beam (7), and installing jacks (12) between the lower ends of the steel pipes (14) and the ground;

two steel brackets (11) are fixedly connected to the two opposite sides of the middle part or the upper part of the frame column (6), two steel frames are arranged below the two steel brackets (11), and each steel frame consists of a steel frame beam (8) horizontally arranged below the frame beam (7) and two vertical steel frame columns (9) fixedly connected below the two ends of the steel frame beam (8); the lower ends of the steel frame columns (9) in the two steel frames are abutted to the ground, and the upper ends of the steel frame beams (8) are connected with the lower ends of the corresponding steel corbels (11) through jacks (12);

step two, erecting a monitoring instrument;

arranging a plurality of laser distance measuring instruments (15) around the frame column (6) on the ground, wherein the laser distance measuring instruments are used for monitoring the rising height of the frame column (6) and the deflection of the frame beam (7) in the jacking process;

thirdly, jacking up the frame column (6);

jacking the frame columns (6) by using the steel brackets (11), the steel frames and the jacks (12), and jacking the frame beams (7) around the corresponding frame columns (6) by using the steel pipes (14) and the jacks (12) synchronously; slowly pressing a jack (12) at the upper end of a steel frame beam (8) and a jack (12) at the lower end of a steel pipe (14) to enable a frame column (6) to rise to a set height and ensure that each frame beam (7) on the periphery reaches a horizontal state, synchronously driving a raft plate foundation (1) subjected to settlement damage to rise upwards in the process of rising the frame column (6), and forming a foundation plate suspension space between the raft plate foundation (1) subjected to settlement damage and a foundation (2);

in the process, the rising height of the frame column (6) is recorded through a laser range finder (15); after the jacking is finished, locking each jack (12);

fourthly, forming a grouting hole A (17-1) and a grouting hole B (17-2);

an inner side grouting area is selected at the central part of the raft plate foundation (1) which is subjected to settlement damage below the frame column (6), and an outer side grouting area is selected at the peripheral part; a plurality of grouting holes A (17-1) are formed in the inner side grouting area in a mode of surrounding the frame column (6), the lower ends of the grouting holes A (17-1) are stopped inside the raft plate foundation (1) subjected to settlement damage, and are communicated with settlement cracks (3) generated on the raft plate foundation (1) subjected to settlement damage; a plurality of grouting holes B (17-2) are formed in the outer grouting area around the frame column (6), and the lower ends of the grouting holes B (17-2) sequentially and vertically penetrate through the foundation (2) and the lower part of the raft plate foundation (1) subjected to settlement damage;

step six, grouting operation;

inserting a grouting steel pipe B (5) into the grouting hole B (17-2), sequentially filling the part below the raft plate foundation (1) which is subjected to settlement damage through compacting grouting of the grouting steel pipe B (5), filling the suspended space of the foundation slab, combining cement paste and soil to form cement soil, enhancing the bearing capacity of the foundation (2), and reconnecting the raft plate foundation (1) which is subjected to overload settlement damage and the original raft plate foundation (1) into a whole; inserting a grouting steel pipe A (4) into the grouting hole A (17-1), and grouting a settlement crack (3) in the raft plate foundation (1) which is damaged by settlement by using the grouting steel pipe A (4) so as to enhance the safety and stability of the raft plate foundation (1) which is damaged by overload settlement;

step seven, planting bars and binding the bars;

selecting a drilling position on the raft foundation (1) and performing drilling operation; then, the lacing wire (19) and the longitudinal bar (20) are implanted into the drilled hole; then the implanted lacing wire (19) and the implanted longitudinal bar (20) are bound;

step eight, repairing the raft foundation (1) and the beam section;

erecting a heightening template at the upper end of the raft foundation (1), erecting a repairing template at the periphery of a cracking part on the frame beam (7), then pouring concrete above the original raft foundation (1) by using the heightening template to form a raft foundation heightening part (18), and pouring concrete at the periphery of the cracking part on the frame beam (7) by using the repairing template to form a repairing surface;

step nine, concrete curing;

curing the poured concrete;

step ten, unloading and removing the steel pipe (14), the steel corbel (11) and the steel frame by using the jack (12);

and (3) after the grouting material in the step nine reaches the design strength, slowly lowering the jack (12), monitoring the settlement condition of each frame column (6) through a laser range finder (15), stopping the lowering of the jack (12) if the frame column (6) has large settlement, and performing rework treatment on the steps seven to nine until no abnormal deformation condition occurs in the process of lowering the jack (12), namely dismantling the steel pipe (14), the steel corbel (11) and the steel frame, dismantling the jack (12) and dismantling the laser range finder (15).

2. The method for repairing and reinforcing a raft foundation according to claim 1, wherein in the first step, the frame columns (6) are provided with accommodating grooves at positions corresponding to the fixing plates at the inner ends of the steel corbels (11), the fixing plates (10) at the inner ends of the steel corbels (11) are embedded in the accommodating grooves, and the steel corbels (11) are fixedly connected to the outer sides of the frame columns (6) through chemical anchor bolts penetrating through the fixing plates (10).

3. The method for repairing and reinforcing a raft foundation according to claim 1 or 2, wherein in step one, the steel tubes (14) are square steel tube columns with square cross sections.

4. The method for repairing and reinforcing a raft foundation according to claim 2, wherein the accommodating grooves are matched with the fixing plate (10) and have a depth of 50mm, and 8 bolt holes with a diameter of 22mm are circumferentially and uniformly arranged on the edge part of the fixing plate (10); the model number of the chemical anchor bolt is M20.

5. The method for repairing and reinforcing a raft foundation according to claim 4, wherein in the sixth step, in the process of filling the suspension space of the foundation slab, grouting holes B (17-2) communicated with the suspension space of the foundation slab are added on the raft foundation (1) damaged by settlement according to the on-site soil body grouting condition for re-grouting until each grouting point cannot continue to eat the grout.

6. A method for repairing and reinforcing a raft foundation according to claim 5, wherein in step seven, the implanted tie bars (19) are

8@450, the implanted longitudinal rib (20) being

14@150。

7. The method for repairing and reinforcing a raft foundation of claim 6, wherein in step seven, before the steel bars are implanted into the drill holes, the wall of each drill hole is brushed by using a steel wire brush, and dust in each hole is completely blown out by extending an air pump into each hole; simultaneously, removing rust on the bonding surface of the steel bar by using a hand grinding wheel until the metallic luster is exposed; and then the cotton yarn is dipped in acetone to wipe the dust on the surface of the steel bar.

8. The method of claim 5, wherein in step eight, the concrete is selected from high-strength non-shrinkage grouting material.