CN106836240B - Basement annular brace construction method for supporting - Google Patents

Abstract

The invention discloses a basement circular support construction method, which is characterized in that the construction steps include: (1) enclosure wall construction; (2) support column construction; (3) making a layer of annular outer support, a layer of annular inner support, concrete truss web, and first-floor support; (4) Excavate the earth to the bottom elevation of the second-floor circular support, make a second-floor circular support, then pour concrete slabs, and finally make the second-floor top support; (5) dig When the soil reaches 10cm below the bottom elevation of the basement floor, make plain concrete cushion first, and then pour concrete for the basement floor; (6) Blast the second-floor ring support, concrete slab, and second-floor roof support, and remove the support columns after the blasting is completed; ( 7) Pouring the roof of the second-floor basement; (8) Blasting the first-floor circular outer support, the first-floor annular inner support, the concrete truss web, and the first-floor roof brace; (9) Pouring the first-floor basement roof.

Description

Construction method of basement circular support

technical field

The invention relates to a support construction method, in particular to a basement annular support construction method.

Background technique

In the basement support system, the internal support structure has the characteristics of safety, reliability, and economical rationality, and is widely used in foundation pit engineering. However, the internal support provided by the conventional support method causes great inconvenience to the excavation of the basement and the construction of the underground structure, resulting in consequences such as prolonged construction period and poor economy. Using ring support instead of the support structure system of the conventional support method can obtain higher economic benefits. However, when the ring support is excavated deeply in the basement, especially when there are multiple supports, the lateral pressure on the first ring support usually exceeds the ultimate compressive strength of the concrete, and the ring support will experience excessive displacement, cracking and other defects in the ring support concrete. Phenomenon.

Contents of the invention

The invention provides a basement circular support construction method to solve the problems in the prior art.

For this reason, the present invention sets up two support systems, the first support is arranged on the top of the basement, and the second support is arranged in the middle of the basement. Since the first support will bear a very large force when the basement is excavated to the bottom elevation, according to the first The stress characteristics of the first support in construction The circular support is made into a truss structure. This structure has high rigidity and strong deformation resistance, while the force of the second support system will be significantly reduced, so the beam type is simply used. ring support. Considering the stress concentration at the corners, the enclosure structure at the four corners and the ring support roof structure are made of concrete slabs to strengthen the rigidity of the corners to resist deformation.

The width of the enclosure wall is 60-80mm, and the depth is 2-3 times of the excavation depth of the basement. The concrete used for the enclosure wall is above C30. The width of the outer support is 30cm, and the height is 40-50cm. The distance between the inner support of the first floor and the outer support of the first floor is 1.2-1.6m. 30cm in height, 40-50cm in height, 30cm in width and 40-50cm in height in the first layer of ring-shaped support, concrete truss webs are set between the ring-shaped outer support of the first layer and the ring-shaped inner support of the first layer, the width of the concrete truss webs is 20cm , with a height of 40 to 50 cm, support columns are set under the first layer of annular inner support and the first layer of annular outer support. The support columns are made of concrete columns or steel columns. .

The second-floor circular support and the roof support structure of the enclosure wall adopt a combination of concrete slabs and roof supports. Concrete slabs are set within 1/4 of the length of the long side of the basement and 1/3 of the length of the short side of the basement, and the middle of the basement is set with a roof. Support, the projection position of the second floor support is the same as that of the first floor support, and the support column of the second floor ring support is the same as the support column of the first floor ring outer support.

The first-floor support extends into the interior of the enclosure wall to form a rigid connection with the enclosure wall, and the second-floor support is welded to the reserved steel bars outside the enclosure wall to form a hinged structure to adapt to the characteristics of the enclosure structure. According to the test results, after the first-floor support and the enclosure wall form a rigid connection, the deformation of the ring support is uniform and relatively small, while the deformation of the enclosure wall is relatively large; after the second-floor support and the enclosure wall form a hinged structure , the deformation is relatively large, but the deformation of the enclosure wall is relatively small.

Construction steps include:

(1) Enclosure wall construction.

The retaining wall should not only protect the slope, but also prevent water seepage. The retaining wall also serves as the basement exterior wall. The construction of the enclosure wall adopts the fasting formwork, and the fasting formwork sinks into the ground through the vertical excitation force generated by the vertical reciprocating vibration of the vibrating hammer, and then fills the hollowing with slurry. The lower end is injected into the slot hole, and the formwork that has sunk into the ground first becomes the guide plate that sinks into the formwork later, and the two formworks show the interlocking effect of the plates, ensuring that the veneers are tightly combined in one plane to form a wall.

Construction techniques include:

1) excavate the reserved groove;

2) Pre-drilled holes;

Pre-drill holes at the junction of the two templates, the diameter of the pre-drilled holes is 90-110cm;

3) Die sinking by vibration;

Start the vibrating hammer, sink the first formwork into the ground to reach the design depth, then place the second formwork closely side by side with the first formwork along the construction axis at the front side of the first formwork, and use the first formwork as a guide plate, sink into the formation to reach the design depth;

4) Perfusion lifts the first template;

Pour the slurry into the first template, and then pour it while lifting it until it is pulled out from the ground, and the slurry remains in the slot hole. After the filling and lifting, keep the slurry reaching the design elevation of the top of the wall;

5) sink into the template again;

Use the second formwork as a guide plate, sink into the ground to reach the design depth, refill and lift the second formwork; follow the above procedures to complete the enclosure wall.

At present, the traditional process is to use a series of processes such as excavation and slotting, mud wall protection, slag removal, underwater concrete pouring, and joint treatment. When slotting in permeable strata, the hole is prone to collapse, and the enclosure wall often does not reach the thickness and broken walls. Phenomenon. However, the present invention sinks the fasting formwork into the soil layer with a strong vertical excitation force, and the formwork and the grout play the role of retaining walls. The body is extruded densely, which improves the impermeability. Because the present invention is finished under the extruding action of former soil body by formwork. And in the process of lifting the formwork while grouting, the grout is injected into the groove from the bottom of the formwork, and the pressure of the grout column is greater than the lateral pressure of the soil, so there will be no shrinkage or collapse of the wall.

(2) Support column construction.

If there is no engineering pile under the support column, first construct the temporary support pile and then insert the support column into the temporary support pile. If there are engineered piles, insert the support columns directly into the temporary support piles.

(3) Make a layer of ring-shaped outer support, a layer of ring-shaped inner support, concrete truss web members, and a layer of top support.

(4) Excavate the soil to the bottom elevation of the second-floor circular support, and make the second-floor circular support. The concrete of the enclosure wall is partially peeled off at the second-floor support, and the reserved steel bars are welded outside the exposed main reinforcement, and then the concrete slab is poured, and finally the second floor is built. support.

(5) Excavate the soil to 10cm below the bottom elevation of the basement floor, make a plain concrete cushion first, and then pour concrete for the basement floor.

When pouring the basement floor construction, the technical scheme of combining dredging and plugging is adopted for the parts with large water inflow, and the method of forced sealing is used for the parts with small water inflow and low water pressure. Concrete mixed with quick-setting agent is poured and pounded internally, and the concrete will solidify in 1-2 minutes. For the case of large water gushing, use a plastic hose to guide water into the sump, and close the sump when the bottom plate of the cap is poured and rammed and reaches 80% strength. The plugging of the sump is carried out as follows: Concentrate water in the steel pipe, the steel pipe diameter is 50mm, and the inner wall of the steel pipe is threaded; screw the screw head into the steel pipe to seal the water pipe, and pour the concrete for the reserved pit on the bottom plate. The inner wall of the reserved pit is provided with grooves for water stop, and the post-cast concrete is mixed with UEA expansion agent to ensure a good combination of old and new concrete.

(6) Blast the second-floor ring support, concrete slab, and second-floor roof support, and remove the support columns after the blasting is completed.

Static blasting is adopted, the expansion force of the expansion material used in static blasting exceeds 30MPa, the diameter of the holes reserved for static blasting is 30-40mm, the distance between the reserved holes is controlled at 0.3-0.4m, and the distance between the reserved holes at the end and the bottom of the structure is 150mm~ 200mm, the area of holes in the cross-section of the member does not exceed 10% of the cross-sectional area; the main reinforcement or stirrup of the reinforced concrete member in the reserved hole is cut to ensure that the binding force of the reinforcement does not affect the blasting effect.

(7) Pouring the roof of the second-floor basement.

(8) Blast the first layer of annular outer support, the first layer of annular inner support, the concrete truss web member, and the first layer of top support.

(9) Pouring a basement roof.

Description of drawings

Figure 1 is a schematic diagram of a circular support structure for a first-floor basement, and Figure 2 is a schematic diagram of a circular support structure for a second-floor basement.

In the attached drawings: 1. Enclosure wall, 2. First floor support, 3. First floor circular outer support, 4. First floor circular inner support, 5. Concrete truss web, 6. Support column, 7. Second floor Layer ring support, 8, concrete slab, 9, second floor support.

Detailed ways

A project is an 18-story building with a frame-tube shear wall structure. The excavation depth of the basement is 7.2m, and the basement is irregular in shape.

In this embodiment, two support systems are set, the first support is set on the top of the basement, the second support is set in the middle of the basement, the first support ring support is made into a truss structure, and the second support system adopts a beam-type ring support. The enclosure structure at the four corners and the ring support roof structure are made into concrete slabs 8 .

The width of the enclosure wall 1 is 70mm, and the depth is 2.5 times of the excavation depth of the basement. The concrete used for the enclosure wall 1 is C30. The width is 30cm, the height is 45cm, the distance between the first layer of annular inner support 4 and the first layer of annular outer support 3 is 1.4m, and a support is set between the first layer of annular outer support 3 and the enclosure wall 1, and the width of the support is 30cm , a height of 45cm, a layer of annular inner support 4 with a width of 30cm and a height of 45cm, a concrete truss web 5 set between a layer of annular outer support 3 and a layer of annular inner support 4, the width of the concrete truss web 5 is 20cm, The height is 45cm, and the support column 6 is set under the first layer of annular inner support 4 and the first layer of annular outer support 3. The support column 6 adopts concrete columns or steel columns. Temporary support piles.

The second-floor ring support 7 and the roof support structure of the enclosure wall 1 adopt a combination of concrete slab 8 and roof support. Concrete slabs are installed within 1/4 of the length of the long side of the basement and 1/3 of the length of the short side. The middle of the basement The top support is set, the projection position of the top support 9 on the second floor is the same as that of the top support 2 on the first floor, and the support column 6 of the ring support 7 on the second floor is the same as the support column 6 of the outer support 3 on the first floor.

The first layer of support extends into the inside of the enclosure wall 1 to form a rigid connection with the enclosure wall 1 , and the second layer of support is welded with the reserved reinforcement outside the enclosure wall 1 to form a hinged structure.

Construction steps include:

(1) Construction of enclosure wall 1.

The construction of enclosure wall 1 uses fasting formwork, and the fasting formwork sinks into the ground through the vertical excitation force generated by the vertical reciprocating vibration of the vibrating hammer, and then fills the fasting with slurry. The lower end of the formwork is injected into the slot hole, and the formwork that has sunk into the ground first becomes the guide plate that sinks into the formwork later, and the two formworks show the interlocking effect of the boards, ensuring that the single boards are tightly combined in one plane to form a wall.

Construction techniques include:

1) excavate the reserved groove;

2) Pre-drilled holes;

Pre-drill a hole at the junction of the two templates, the diameter of the pre-drilled hole is 100cm;

3) Die sinking by vibration;

Start the vibrating hammer, sink the first formwork into the ground to reach the design depth, then place the second formwork closely side by side with the first formwork along the construction axis at the front side of the first formwork, and use the first formwork as a guide plate, sink into the formation to reach the design depth;

4) Perfusion lifts the first template;

Pour the slurry into the first template, and then pour it while lifting it until it is pulled out from the ground, and the slurry remains in the slot hole. After the filling and lifting, keep the slurry reaching the design elevation of the top of the wall;

5) sink into the template again;

Use the second formwork as a guide plate, sink into the ground to reach the design depth, refill and lift the second formwork; follow the above procedures to complete the enclosure wall 1.

(2) Construction of support column 6 .

If there is no engineering pile below the support column 6, the support column 6 is inserted into the temporary support pile after the construction of the temporary support pile earlier. If there is an engineering pile, the support column 6 is directly inserted into the temporary support pile.

(3) Make a layer of annular outer support 3, a layer of annular inner support 4, a concrete truss web member 5, and a layer of top support 2.

(4) Excavate the soil to the bottom elevation of the second-floor circular support 7, and make the second-floor circular support 7. The enclosure wall 1 partially peels off the concrete at the second-floor support, welds the reserved reinforcement outside the exposed main reinforcement, and then pours the concrete slab 8, Finally, do the second floor support 9.

(5) Excavate the soil to 10cm below the bottom elevation of the basement floor, make a plain concrete cushion first, and then pour concrete for the basement floor.

When pouring the basement floor construction, the technical scheme of combining dredging and plugging is adopted for the parts with large water inflow, and the method of forced sealing is used for the parts with small water inflow and low water pressure. Concrete mixed with quick-setting agent is poured and pounded internally, and the concrete will solidify in 1-2 minutes. For the case of large water gushing, use a plastic hose to guide water into the sump, and close the sump when the bottom plate of the cap is poured and rammed and reaches 80% strength. The plugging of the sump is carried out as follows: Concentrate water in the steel pipe, the diameter of which is 50 mm, and the inner wall of the steel pipe is threaded; screw the screw head into the steel pipe to seal the water pipe, and pour the concrete for the reserved pit on the bottom plate. The inner wall of the reserved pit is provided with grooves for water stop, and the post-cast concrete is mixed with UEA expansion agent to ensure a good combination of old and new concrete.

(6) Blast the second-floor ring support 7, the concrete slab 8, and the second-floor roof support 9, and remove the support column 6 after the blasting is completed.

Static blasting is adopted, the expansion force of the expansion material used in static blasting is 35MPa, the diameter of the hole reserved for static blasting is 35mm, the distance between the reserved holes is controlled at 0.3-0.4m, the reserved position of the end hole is 200mm from the bottom of the structure, and the transverse The area of holes on the cross-section shall not exceed 10% of the cross-sectional area; the main bars or stirrups of reinforced concrete members in the reserved holes shall be cut off to ensure that the binding force of the steel bars does not affect the blasting effect.

(7) Pouring the roof of the second-floor basement.

(8) Blast the first layer of annular outer support 3, the first layer of annular inner support 4, the concrete truss web 5, and the first layer of top support 2.

(9) Pouring a basement roof.

Through computer simulation analysis, this structure is compared with other support systems. The first case is to adopt this embodiment, the second case is to simply adopt inner support, and the third case is to adopt ring support on the first and second floors. Table 1 is a comparison of the displacement and mechanical properties of different support systems. It is found in the table that the maximum horizontal displacement of the support in this embodiment is far smaller than that of the second case and the third case, which are 38.6% of the second case, which is the second case. 57.9% of the two cases. The maximum axial force of this embodiment is significantly reduced, being 59.6% and 79.9% of the second case, respectively. The maximum bending moment of this embodiment is significantly reduced, being 62.8% and 79.0% of the second case, respectively.

Table 1 Comparison of displacement and mechanical properties of different support systems

According to the on-site inspection, the structure of the basement is stable during the construction process, the support displacement does not exceed 11mm, the support beam structure is stable, and no abnormal phenomenon occurs.

Claims (1)

1. A basement circular support construction method, characterized in that two support systems are set, the first support is arranged on the top of the basement, the second support is arranged in the middle of the basement, and the first support annular support is made into a truss structure , the second support system adopts beam-type ring support; the enclosure structure at the four corners and the ring support roof structure are made of concrete slabs; The width of the enclosure wall is 60-80mm, and the depth is 2-3 times of the excavation depth of the basement. The concrete used for the enclosure wall is above C30. The width of the outer support is 30cm, and the height is 40-50cm. The distance between the inner support of the first floor and the outer support of the first floor is 1.2-1.6m. 30cm in height, 40-50cm in height, 30cm in width and 40-50cm in height in the first layer of ring-shaped support, concrete truss webs are set between the ring-shaped outer support in the first layer and the ring-shaped inner support in the first layer, the width of the concrete truss webs is 20cm , with a height of 40-50cm, a support column is set under the first layer of annular inner support and the first layer of annular outer support. The support column is a concrete column or a steel column, and the support column is set on the engineering pile, otherwise a temporary support pile is set under the support column; The second-floor circular support and the roof support structure of the enclosure wall adopt a combination of concrete slabs and roof supports. Concrete slabs are set within 1/4 of the length of the long side of the basement and 1/3 of the length of the short side of the basement, and the middle of the basement is set with a roof. support, the projected position of the top support on the second floor is the same as that of the top support on the first floor, and the support columns of the circular support on the second floor are the same as the support columns of the circular outer support on the first floor; Construction steps include: (1) Enclosure wall construction; The construction of the enclosure wall adopts the fasting formwork, and the fasting formwork sinks into the ground through the vertical excitation force generated by the vertical reciprocating vibration of the vibrating hammer, and then fills the hollowing with slurry. The lower end is injected into the slot hole, and the formwork that has sunk into the ground first becomes the guide plate that sinks into the formwork later, and the two formworks show the interlocking effect of the plates, ensuring that each single plate body is tightly combined to form a wall in a plane; (2) Support column construction; If there is no engineering pile under the support column, first construct the temporary support pile and then insert the support column into the temporary support pile; if there is an engineering pile, directly insert the support column into the temporary support pile; (3) Make a layer of ring-shaped outer support, a layer of ring-shaped inner support, concrete truss web members, and a layer of top support; (4) Excavate the soil to the bottom elevation of the second-floor circular support, and make the second-floor circular support. The concrete of the enclosure wall is partially peeled off at the second-floor support, and the reserved steel bars are welded outside the exposed main reinforcement, and then the concrete slab is poured, and finally the second floor is built. support; (5) Excavate the soil to 10cm below the bottom elevation of the basement floor, make a plain concrete cushion first, and then pour concrete for the basement floor; (6) Blast the second-floor ring support, concrete slab, and second-floor roof support, and remove the support columns after the blasting is completed; (7) Pouring the roof of the second-floor basement; (8) Blasting the first layer of annular outer support, the first layer of annular inner support, the concrete truss web member, and the first layer of support; (9) Pouring a basement roof.