CN209760290U - Full-covering type pile foundation underpinning node - Google Patents

Abstract

The utility model provides an all-inclusive pile foundation underpinning node, which belongs to the technical field of civil engineering and includes an underpinning beam used to cover all existing caps, existing piles and support columns and an underpinning beam used to carry The underpinning pile, the connection surface between the underpinning beam and the existing cap is horizontally implanted with a number of connecting steel bars, and there are a number of matching grooves and grooves, and there are ordinary steel bars and some prestressed steel bars in the underpinning beam The underpinning pile is set under the underpinning beam to lift the underpinning construction and bear the underpinning beam, and finally form a new pile foundation. The utility model has a reasonable design and realizes all-inclusive, multi-dimensional pile foundation underpinning The reliable connection of the nodes effectively increases the shear contact area between the underpinning beam and the existing cap, reduces the interface slippage of the underpinning node, improves the integrity of the underpinning node, and avoids damage to the pier of the main bearing member. / column damage, reducing the engineering risk.

Description

An all-inclusive pile foundation underpinning node

technical field

The utility model belongs to the technical field of civil engineering, in particular to an all-inclusive pile foundation underpinning node.

Background technique

Pile foundation underpinning technology is the core technology for developing the underground space of existing buildings. In recent years, the construction of a large number of subways in my country has promoted the application and development of this technology, making it a solution to the problem of lines crossing existing building pile foundations in the construction of urban subways. An important technical means of construction problems. During the development of underground space, the structural form of the existing buildings, the size of the load, the importance of the underlying buildings, the control of engineering costs, the control of building deformation, and the conditions of the construction environment are all different, which makes the design of underpinning node connections very important. The difference, complexity and specificity of the existing technology mostly adopt the method of placing the existing cap on the upper end of the underpinning beam or wrapping the support column with the underpinning beam. The connection surface between it and the underpinning beam is small, and the Poor reliability, prone to slippage, and poor integration of post-cast underpinning beams with existing caps/support columns.

Utility model content

The purpose of the utility model is to provide an all-inclusive pile foundation underpinning node, which realizes reliable connection of all-inclusive, multi-dimensional pile foundation underpinning nodes.

The purpose of this utility model is achieved through the following technical solutions:

An all-inclusive pile foundation underpinning node, including support columns, existing caps and existing piles, the existing caps are set under the support columns to receive the support columns, and the existing piles are set on The underside of the existing cap is used to accept the existing cap; it includes underpinning beams and underpinning piles; the surrounding side walls of the existing cap are provided with several grooves extending in the horizontal direction, and the surface of the existing cap is chiseled There are several dents, the surrounding side walls of the existing cap, the side walls of the lower end of the supporting column, and the side walls of the upper end of the existing piles are horizontally provided with connecting steel bars for connecting the underpinning beams, and the underpinning beams are poured Cover the existing cap and pour the lower end of the cladding support column and the upper end of the existing pile at the same time. The underpinning beam is equipped with ordinary steel bars and several prestressed steel beams. The underpinning pile is set under the underpinning beam to carry Underpinning beam.

In any direction, the difference between the outer diameter of the underpinning beam and the outer diameter of the existing platform is ≥ 600 mm, and the existing platform is located at the center of the underpinning beam.

Further, the contact surface between the support column and the underpinning beam, and the contact surface between the existing pile and the underpinning beam are all chiseled with dents 2 .

Further, the depth of the first dent and the second dent is 0.5-1.5 cm.

Further, the depth of the groove is 3-7cm, and the width of the groove is 10-20cm.

Further, the connecting steel bars are connected to the supporting columns, the existing piles and the existing caps through horizontal drilled holes, and are fixed by construction glue.

Further, the prestressed steel tendons include several first prestressed steel tendons and several second prestressed steel tendons, the first prestressed steel tendons are arranged on both sides of the existing platform, and the second prestressed steel tendons The stress steel beam is arranged under the existing platform.

Further, the first prestressed steel strands and the second prestressed steel strands are arc-shaped steel strands with the arcs facing outward, and the middle sections of the arcs of the first prestressed steel strands and the second prestressed steel strands In a straight line.

Further, construction glue is provided between the underpinning beam and the supporting column, between the underpinning beam and the existing pile, between the underpinning beam and the existing cap, and the concrete grade of the underpinning beam is high Concrete grade for existing caps.

Compared with the prior art, the utility model has the beneficial effects of:

The underpinning node of the utility model is simple to manufacture, low in production cost, wide in scope of application, and high in application value. The underpinning beam fully covers the existing cap, forming a wrapping force on the existing cap, effectively increasing the underpinning beam The contact area between the underpinning beam and the existing cap improves the integrity of the underpinning beam and the existing cap; and by setting the groove on the side of the existing cap of the pile foundation, the mechanical bite force of the underpinning node connection is increased; The surface of the existing cap is chiseled, and connecting steel bars are implanted on the side of the existing cap to increase the force of the pin bolts connecting the underpinning beam to the existing cap; prestressed steel beams are arranged around the existing cap to The friction resistance of the connection between the underpinning beam and the existing cap is increased, and the above multiple shearing measures are adopted to realize the reliable connection of the all-inclusive, multi-dimensional pile foundation underpinning node, and solve the problem of large tonnage and small deformation of the underpinning node It can minimize or even avoid damage to the pier/column of the main load-bearing member, effectively reducing the engineering risk.

Description of drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following drawings will be briefly introduced in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention. Therefore, it should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained according to these drawings without creative work.

Fig. 1 is a working schematic diagram of the all-inclusive pile foundation underpinning node provided by the first embodiment of the utility model;

Fig. 2 is the front view of the underpinning beam provided by the first embodiment of the utility model;

Fig. 3 is a side view of the underpinning beam provided by the first embodiment of the utility model;

Fig. 4 is a top view of the underpinning beam provided by Embodiment 1 of the present invention;

Reference signs: 1-support column, 2-existing cap, 21-groove, 22-connecting steel bar, 23-drilling, 3-existing pile, 4-underpinning beam, 41-first prestress Steel beam, 42-second prestressed steel beam, 5-underpinning pile, 1000 superstructure, 2000-cover beam, 3000-tunnel structure.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the utility model more clear, the technical solutions in the embodiments of the utility model will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the utility model. Obviously, the described The embodiments are some embodiments of the present utility model, but not all embodiments. The components of the embodiments of the invention generally described and illustrated in the figures herein may be arranged and designed in a variety of different configurations.

Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present utility model, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the scope of protection of the present utility model.

It should be noted that like numerals and letters denote similar items in the following figures, therefore, once an item is defined in one figure, it does not require further definition and explanation in subsequent figures.

The terms "first", "second", "third", etc. are only used for distinguishing descriptions, and should not be construed as indicating or implying relative importance.

Furthermore, the terms "parallel", "perpendicular", etc. do not mean that the components are absolutely parallel or perpendicular, but may be slightly inclined. For example, "parallel" only means that its direction is more parallel than "vertical", and does not mean that the structure must be completely parallel, but can be slightly inclined.

In the description of the present utility model, it should also be noted that, unless otherwise specified and limited, the terms "setting", "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection , can also be detachably connected, or integrally connected; can be directly connected, can also be indirectly connected through an intermediary, and can be internal communication between two components. Those of ordinary skill in the art can understand the specific meanings of the above terms in the present utility model in specific situations.

Embodiment one

As shown in Figures 1 to 4, an all-inclusive pile foundation underpinning node includes a support column 1, an existing cap 2 and an existing pile 3, and the existing cap 2 is set under the support column 1 to accept The support column 1 and the existing pile 3 are set under the existing cap 2 to support the existing cap 2; including the underpinning beam 4 and the underpinning pile 5; the surrounding side walls of the existing cap 2 are provided with several horizontal The groove 21 extending in the direction, the depth of the groove 21 is 3～7cm, the width of the groove 21 is 10～20cm, and the surface of the existing platform 2 is chiseled with some dents 1, and the depth of the dent 1 is 0.5～1.5cm. cm, the surrounding side walls of the existing cap 2, the side walls of the lower end of the support column 1, and the upper end of the existing pile 3 are all horizontally provided with connecting steel bars 22 for connecting the underpinning beam 4, and the underpinning beam 4 is poured Covering the existing cap 2 and pouring the lower end of the supporting column 1 and the upper end of the existing pile 3 at the same time, a number of prestressed steel beams are arranged in the underpinning beam 4, and the underpinning pile 5 is arranged under the underpinning beam 4 for To carry the underpinning beam 4.

When the span of the underpinning beam 4 is large (that is, when the distance between the underpinning piles 5 on both sides is relatively long), a through hole is opened in the horizontal direction at the lower end of the existing pile 3, and a steel cable is threaded in the through hole, and the two ends of the steel cable The two ends of the underpinning beam 4 are fixedly connected to form a tension beam structure, which effectively reduces the bending moment of the underpinning beam.

The utility model fully wraps the existing bearing platform through the underpinning beam, forms a wrapping force on the existing bearing platform, effectively increases the contact area between the underpinning beam and the existing bearing platform, and improves the performance of the underpinning beam and the existing bearing platform. Integrity; and by setting grooves on the side of the existing cap of the pile foundation, the mechanical bite force of the underpinning joint connection is increased; the surface of the existing cap is chiseled, and the connecting steel is implanted on the side of the existing cap The strips increase the force of the pin bolts connecting the underpinning beam to the existing cap; the prestressed steel beams are set around the existing cap to increase the frictional resistance of the connection between the underpinning beam and the existing cap. The anti-shear measures realize the reliable connection of all-inclusive, multi-dimensional pile foundation underpinning nodes, solve the connection problems of large tonnage, small deformation and interface slippage of the underpinning nodes, and at the same time minimize or even avoid damage to the underpinning nodes. Damage to the pier/column of the main load-bearing member effectively reduces the engineering risk.

In some embodiments, in any direction, the difference between the outer diameter of the underpinning beam 4 and the outer diameter of the existing platform 2 is ≥ 600mm, and the existing platform 2 is located at the center of the underpinning beam 4; as shown in Figure 1 , that is, the distance from the bottom surface of the underpinning beam 4 to the bottom surface of the existing cap 2 is ≥300, the distance from the top surface of the underpinning beam 4 to the top surface of the existing cap 2 is ≥300, and the front of the underpinning beam 4 to the existing The distance from the front of the cap 2 is ≥300, and the distance from the back of the underpinning beam 4 to the back of the existing cap 2 is ≥300. The above design effectively ensures that the underpinning beam 4 wraps around the existing cap 2 Wholeness.

In some embodiments, the contact surface between the support column 1 and the underpinning beam 4, and the contact surface between the existing pile 3 and the underpinning beam 4 are all chiseled with a dent 2, and the depth of the dent 2 is 0.5-1.5 cm, because The underpinning beam 4 is poured after the support column 1 and the existing pile 3, and the underpinning beam 4 wraps the upper end of the existing pile 3 and the lower end of the support column 1 inside. The above design can make the underpinning There is a better connection effect between the replacement beam 4 and the support column 1 and the existing pile 3 .

In some embodiments, the connecting steel bar 22 is connected to the support column 1, the existing pile 3, and the existing cap 2 through the horizontally arranged drill holes 23, and is fixed by construction glue. Since the support column 1, the existing cap 2 and the existing pile 3 are built before the underpinning beam 4, in order to make the underpinning beam 4 and the support column 1, the existing cap 2, and the existing pile 3 have better connection strength, a connection is added at the connection Steel bar 22, and the support column 1, existing cap 2, and existing pile 3 were not preset in the early stage, so it is necessary to plant connecting steel bars 22 on the support column 1, existing pile 3, and existing cap 2 , and the above method is a relatively simple, fast and reliable way of planting bars.

In some embodiments, the prestressed steel tendons include several first prestressed steel tendons 41 and several second prestressed steel tendons 42, the first prestressed steel tendons 41 are arranged on both sides of the existing platform 2, and the second prestressed steel tendons The steel beam 42 is arranged under the existing platform 2; by arranging the first prestressed steel beam 41 and the second prestressed steel beam 42 on both sides and below the existing platform 2, and stretching them, and then On the whole, the horizontal prestress pointing to the existing cap 2 and the vertical prestress vertically pointing to the existing cap 2 are generated. The transverse prestress makes the new cap structure produce a binding force on the existing cap 2, so that The new and old structures are closely connected to jointly bear the load after the structure is formed, and the vertical prestress can offset the tensile stress generated at the lower edge of the existing cap 2 when it is loaded.

In some embodiments, the second prestressed steel beam 42 includes two protruding ends protruding from the underpinning beam 4, and the two ends of the steel cables passing through the horizontal through holes at the lower end of the existing pile 3 are respectively connected to the two protruding ends. , using the above method, if the existing cap 2 slips downward, the steel cable will tighten the second prestressed steel beam 42, so that it will generate an upward force on the existing cap 2, effectively resisting the existing cap 2 Swipe down.

In some embodiments, the first prestressed steel tendons 41 and the second prestressed steel tendons 42 are arc-shaped steel tendons whose arc arches face outward, and the arcs of the first prestressed steel tendons 41 and the second prestressed steel tendons 42 The middle section of the arch is straight; when the first prestressed steel tendon 41 is stretched, the first prestressed steel tendon 41 will generate a bridge in the width direction of the newly built cap 2 from the underpinning beam 4 to the existing cap. 2, and then make the underpinning beam 4 produce opposite bonding force on the two ends of the existing cap 2, so that the new and old structures are closely connected, and jointly bear the load after the structure is formed.

In some embodiments, the first prestressed steel tendons 41 and the second prestressed steel tendons 42 are arc-shaped steel tendons whose arc arches face outward, and the arcs of the first prestressed steel tendons 41 and the second prestressed steel tendons 42 The middle section of the arch is linear; the first prestressed steel beam 41 and the second prestressed steel beam 42 both sides are arc-shaped, and the middle section is straight, when the first prestressed steel beam 41 and the second prestressed steel beam 41 and the second After the prestressed steel tendon 42 is stretched, the first prestressed steel tendon 41 and the second prestressed steel tendon 42 in the linear part will generate prestress. After removing the pile foundation of the existing cap 2 and using the underpinning beam 4. During underpinning, the prestress can offset the tensile stress generated at the lower edge of the existing bearing platform 2 when it is under load, and the first prestressed steel tendons 41 and the second prestressed steel tendons 42 in the arc shape can be easily In the length direction of the underpinning beam 4, there will be a prestress force pointing from the underpinning beam 4 to the existing cap 2, and then the underpinning beam 4 will produce opposite bonding force on the two ends of the existing cap 2, so that the new and old The structure is closely connected and jointly bears the load after the structure is formed; the first prestressed steel tendon 41 and the second prestressed steel tendon 42 of the arc-shaped part are stretched, so that the existing cap 2 is in a state of four-way stress, Even if the four directions of the existing cap 2 are subjected to the force from the underpinning beam 4 on the existing cap 2, the force can be better transmitted between the new and old structures, and the bearing capacity of the structure can be further improved.

In some embodiments, construction glue is provided between the underpinning beam 4 and the support column 1, between the underpinning beam 4 and the existing pile 3, between the underpinning beam 4 and the existing cap 2, and the concrete of the underpinning beam 4 The grade is higher than the concrete grade of the existing cap 2; the above design makes the underpinning beam 4 poured later and the support column 1 poured earlier, the existing pile 3, and the existing cap 2 have a better bonding effect, The connection strength is higher.

A construction method for an all-inclusive pile foundation underpinning node as described above, the construction steps are as follows:

S1. Digging the foundation pit to expose the pile foundation and ensure the stability of the pile foundation during excavation;

S2. make rebate 21 on the side of existing cap 2, rebate depth 5cm, height 15cm;

S3. Chiseling the entire surface of the existing cap 2, the lower side of the supporting column 1, and the upper side of the existing pile 3 to a depth of 1 cm, and strictly controlling the chiseling depth during the chiseling process;

S4. Drill holes 23 on the side of the existing cap 2, the lower side of the support column 1, and the upper side of the existing pile 3, pour construction glue into them, and implant connecting steel bars; Change the load to design;

S5. Make reinforcement cages, and arrange prestressed steel tendons on each side of the existing cap 2. Several prestressed steel tendons are used on each side of the cap platform, and several prestressed steel tendons are arranged on each of the bottom two layers of the cap. The specific arrangement of the steel tendons depends on the The number and position are designed according to the actual underpinning load;

S6. Spray construction glue on the entire surface of the existing cap 2;

S7. Concrete is poured and maintained, and underpinning piles 5 and underpinning beams 4 are sequentially built to form an underpinning system. The grade of newly poured concrete should be higher than that of the existing cap;

S8. After the underpinning beam is maintained to a certain strength, stretch the prestressed steel beam to the preset pre-camber. The tensioning sequence is from top to bottom, symmetrical tensioning, and the tensioning control method adopts ordinary prestressed concrete post-tensioning method;

S9. Jack up the underpinning beam 4, cut off the existing pile 3 after the settlement and deformation of the underpinning beam system is stable, connect the underpinning beam 4 and the underpinning pile 5 with cast-in-place concrete, form a new pile foundation, and complete the underpinning .

Compared with the experimental design of previous scholars, the scale of the test piece is generally small, and the reduction of the concrete area caused by the uneven distribution of the shear stress is ignored. However, the shear surface of the pile foundation underpinning node joint is relatively large, and the shear stress should be considered in the calculation. Because of the influence of uneven distribution, the effective height of the underpinning node interface is reduced, and the calculation formula is as follows:

Considering that the new and old concrete interface of this underpinning node is a potential bonding weak surface, which is different from the whole cast-in-place concrete, the formula for calculating the bond shear strength value of the new and old concrete interface is as follows:

f _ctd =0.7f _t

The formula for calculating the shear resistance provided by the connecting reinforcement at the upper interface of the old and new concrete is as follows:

V _s ＝A _s f _yd (μsinα'+cosα')

The underpinning beam is a cast-in-place integral reinforced concrete prestressed simply supported beam, and the shear effect of the stirrup at the joint interface cannot be ignored. At the same time, since the underpinning beam is a deep beam, the calculation formula for the shear capacity of the deep beam is as follows:

The frictional resistance between the old and new concrete interface is obtained by multiplying the axial pressure provided by the prestressed steel beam on the old and new interface by the friction coefficient, and the calculation formula is as follows:

N _eff ＝0.64A _s σ _com ＝0.64×0.7A _s f _ptk

Considering that the underpinning beam is an "all-inclusive" underpinning beam node, and its "wrapping effect" is reflected by the cast-in-place concrete as a whole, the concrete bonding force of the outsourcing part is calculated according to the cast-in-place concrete component, and the calculation formula is as follows:

According to the above analysis of various factors of shear resistance of pile foundation underpinning interface, due to the existence of weak interface between old and new concrete, the shear resistance factors of underpinning node interface play different roles in different stages and change with the increase of underpinning load. At the beginning of the underpinning, the load is small, and the interface has no initial slippage. The shear bearing capacity is mainly provided by the cohesive force formed by the "wrapping force", the mechanical bite force of the groove and the pre-compression friction resistance; when the load exceeds the initial slippage Bearing capacity, interface slippage, cohesive force failure, and interface shear resistance are mainly realized by pre-compression friction resistance, stirrup shear action and connecting steel bar action.

Therefore, the calculation formula of the interface shear bearing capacity of the all-inclusive pile foundation underpinning beam is as follows:

Interface initial sliding bearing capacity:

Ultimate shear capacity:

In the above formula, λ is the shear-span ratio of the underpinning beam, f _t is the design value of the tensile strength of the concrete, which is the lower value among the new and old members; b is the section width; h ₀ is the effective height of the overall pouring section; f _yv is Design value of the tensile strength of shear reinforcement; A _sv is the area of shear reinforcement; s is the spacing of shear reinforcement along the length direction; f _ctd is the design value of concrete shear strength _{f ctd} = 0.7f _t ; Plane area, take 2/3 of the interface area; N is the axial force perpendicular to the shear plane that exists at the same time as the shear force, compression is positive and tension is negative, and N≤0.6f _ctd A _c , when N is tension, take f _ctd = 0; N _eff is the effective control of prestress, the prestress uses Φ _s 1860 grade steel strand, the area of the steel strand is A _s , the control stress σ _com under the anchor is 0.7f _ptk , considering various prestress losses, the permanent stress The ratio of A s to the control stress under anchor is 0.64; A _s is the area of the shear reinforcement; f _yd is the yield strength of the shear reinforcement; f _cd is the design value of the concrete compressive strength; α' is the distance between the shear reinforcement and the shear plane Angle, 45°≤α'≤90°; c and μ are the roughness coefficients of the old and new interfaces, and the values of c and μ are as follows:

Note: The rough interface in the table requires at least 3mm rough depth and 40mm width.

The above are only preferred embodiments of the present utility model, and are not intended to limit the present utility model. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present utility model should be included in the utility model. within the scope of protection.

Claims (9)

1. A full-covering type pile foundation underpinning node comprises a supporting column (1), an existing bearing platform (2) and an existing pile (3), wherein the existing bearing platform (2) is arranged below the supporting column (1) and used for bearing the supporting column (1), and the existing pile (3) is arranged below the existing bearing platform (2) and used for bearing the existing bearing platform (2); the method is characterized in that: comprises a underpinning beam (4) and an underpinning pile (5); the novel bearing platform is characterized in that a plurality of grooves and tongues (21) extending in the horizontal direction are formed in the peripheral side wall of the existing bearing platform (2), a plurality of first dents are chiseled on the surface of the existing bearing platform (2), a plurality of connecting steel bars (22) used for being connected with the underpinning beam (4) are horizontally arranged on the peripheral side wall of the existing bearing platform (2), the side wall of the lower end of the supporting column (1) and the side wall of the upper end of the existing pile (3), the underpinning beam (4) is poured and coated on the existing bearing platform (2) and is simultaneously poured and coated on the lower end of the supporting column (1) and the upper end of the existing pile (3), a plurality of prestressed steel bundles are arranged in the underpinning beam (4), and the underpinning pile (5) is arranged below the underp.

2. The fully-encased pile foundation underpinning node of claim 1, further comprising: in any direction, the difference between the length of the underpinning beam (4) and the length of the existing bearing platform (2) is more than or equal to 600mm, and the existing bearing platform (2) is positioned in the center of the underpinning beam (4).

3. The fully-encased pile foundation underpinning node of claim 1, further comprising: and the contact surfaces of the support columns (1) and the underpinning beam (4) and the contact surfaces of the existing piles (3) and the underpinning beam (4) are all chiseled with dents II.

4. The fully-encased pile foundation underpinning node of claim 3, wherein: the depth of the first dent and the second dent is 0.5-1.5 cm.

5. the fully-encased pile foundation underpinning node of claim 1, further comprising: the depth of the rabbet (21) is 3-7 cm, and the width of the rabbet (21) is 10-20 cm.

6. The fully-encased pile foundation underpinning node of claim 1, further comprising: the connecting steel bar (22) is connected with the supporting column (1), the existing pile (3) and the existing bearing platform (2) through a drill hole (23) horizontally arranged and is fixed by building glue in a bonding mode.

7. The fully-encased pile foundation underpinning node of claim 1, further comprising: the prestressed steel bundles comprise a plurality of first prestressed steel bundles (41) and a plurality of second prestressed steel bundles (42), the first prestressed steel bundles (41) are arranged on two sides of the existing bearing platform (2), and the second prestressed steel bundles (42) are arranged below the existing bearing platform (2).

8. The fully-encased pile foundation underpinning node of claim 7, wherein: the first prestressed steel beam (41) and the second prestressed steel beam (42) are arc-shaped steel beams with arc arches facing outwards, and the middle sections of the arc arches of the first prestressed steel beam (41) and the second prestressed steel beam (42) are linear.

9. The fully-encased pile foundation underpinning node of claim 1, further comprising: building glue is arranged between the underpinning beam (4) and the support column (1), between the underpinning beam (4) and the existing pile (3), between the underpinning beam (4) and the existing bearing platform (2), and the concrete grade of the underpinning beam (4) is higher than that of the existing bearing platform (2).