CN115233689A - Combined type enclosure structure for soft soil foundation pit and construction method thereof - Google Patents

Abstract

The invention discloses a combined enclosure structure for a foundation pit in soft soil and a construction method thereof. The tops of the piles are connected in a straight line, and the tops of the piles are connected by capping beams; the bottom of the inclined piles is deep into the soil inside the foundation pit, and a capping plate is poured on the top. One end of the recoverable anchor rod obliquely passes through the first connecting through hole and the second connecting through hole in sequence and is inserted into the soil outside the foundation pit to limit the lateral displacement of the inclined pile and the retaining pile. Compared with the traditional vertical pile, the present invention bears the horizontal load through the inclined pile, which greatly improves the mechanical performance of the pile body; in addition, a soil reinforcement area is arranged at the bottom of the inclined pile to improve the properties of the soft soil and actively utilize the tensile force of the anchor rod. Sharing the lateral pressure acting on the inclined pile can limit the lateral displacement of the inclined pile and reduce the stress on the soil reinforcement area at the root of the inclined pile.

Description

A combined enclosure structure for foundation pits on soft soil and its construction method

technical field

The invention belongs to the technical field of construction engineering foundation pit enclosure, in particular to a combined enclosure structure for a soft soil foundation pit and a construction method thereof.

Background technique

With the rapid development of my country's economy and the continuous advancement of urban construction, the foundation pit project has developed in the direction of larger scale and deeper depth. The foundation pit enclosure structure plays a key role in ensuring the safety of the foundation pit and adjacent buildings.

At present, common foundation pit enclosure structures mainly include grading excavation, cantilever structure, internal support structure, pile-anchor structure, etc., but the above enclosure structures have certain limitations. Grading excavation is suitable for projects with good foundation soil quality and sufficient grading space on the construction site; cantilever structure construction speed is fast, but the rigidity is small, and it is suitable for foundation pits with shallow excavation depth; A large number of supporting piles and supporting beams need to be installed in large-scale foundation pits, which is expensive and difficult to support; the pile-anchor structure in soft soil foundation pits has problems such as poor ability to control deformation due to low pull-out bearing capacity of anchor rods .

Soft soil is widely distributed in my country's coastal areas. Soft soil has the characteristics of high water content, high compressibility, low bearing capacity, and low shear strength, and it is prone to settlement deformation under load. In order to prevent accidents in foundation pit engineering in soft soil areas, it is necessary to select a suitable foundation pit enclosure structure for deformation control to ensure the stability of the foundation pit. At present, the containment methods for soft soil foundation pits are still not perfect, especially for large-scale deep foundation pit projects, the ability of a single containment method to control deformation is often very limited.

Contents of the invention

In order to solve the above-mentioned technical problems existing in the prior art, the present invention provides a combined enclosure structure for foundation pits on soft soil and its construction method. The present invention does not require horizontal internal supports, and has high safety, economy, Environmental protection and other advantages.

The technical scheme that the present invention adopts is as follows:

A combined enclosure structure for foundation pits on soft ground, characterized in that it comprises:

Enclosure piles, a plurality of enclosure piles are vertically inserted at the edge of the foundation pit for retaining soil and water stop; the centers of the pile tops are connected in a straight line, and the pile tops are connected by a pressure beam; each enclosure pile extends into The part of the soil is provided with a first connection through hole connected with the recoverable anchor rod;

Inclined piles, set at an angle, the bottom of the inclined piles goes deep into the soil inside the foundation pit, the lower end is provided with a second connection through hole connected with the recyclable anchor rod, the top is poured with a top plate, and the top plate is fixedly connected with the top beam to secure the surrounding protection piles. , inclined piles, roof slabs and roof beams are integrated to form a combined enclosure structure;

The retrievable anchor rod is installed obliquely; one end of the retrievable anchor rod is inserted obliquely through the first connecting through hole and the second connecting through hole in the outer soil of the foundation pit to limit the oblique pile and the enclosure lateral displacement of the pile;

The soil reinforcement area is set around the bottom of the inclined pile to limit the displacement of the inclined pile.

Further, the soil reinforcement area is a cement mixing reinforcement formed at the bottom of the inclined pile by means of high-pressure rotary spraying or forced grouting.

Further, the inclined piles are prefabricated reinforced concrete pipe piles or I-shaped piles, and the angle between the inclined piles and the vertical direction is between 20° and 60°; the inclined piles are arranged at equal intervals and parallel to each other, and the pile ends at the lower Go deep into the soil layer below the bottom of the pit.

Further, the surrounding protection piles are vertical row piles, and the row piles adopt bored piles, SMW piles, prefabricated reinforced concrete I-shaped or section steel.

Further, the roofing beam is a cast-in-place strip structure, the roofing plate is cast-in-place above the inclined piles, the width of the roofing beam is greater than the pile diameter of the surrounding protection piles, and the width of the roofing plate is greater than the pile diameter of the inclined piles.

Further, the soil reinforcement area adopts grouting reinforcement method, cement-soil mixing pile reinforcement method or high-pressure rotary jetting reinforcement method.

Adopt the construction method of above-mentioned combined type enclosure structure, it is characterized in that, concrete construction steps are as follows:

Step 1: Construction of soil reinforcement area

Use grouting reinforcement method, cement-soil mixing pile reinforcement method or high-pressure rotary grouting reinforcement method to strengthen the soil in the design area, improve the shear strength of soft soil, reduce the lateral displacement after the inclined pile is driven, and improve the slope of the inclined pile. Anti-lateral bearing capacity;

Step 2: Construction of inclined piles and retaining piles

The inclined piles and vertical row piles are driven into the design area by static pressure method or high-pressure jet spraying method. The number, row number, angle and length of the inclined piles are determined according to the actual situation, and the vertical row piles are constructed to form enclosure piles;

Step 3: Construction of roof beams and roof panels

Excavate to the bottom of the design position of the roofing beam, construct the roofing beam of the enclosure pile and the roofing plate of the inclined pile, and pour the roofing beam and the roofing plate to realize the integration of the enclosure pile, the inclined pile, the roofing plate and the roofing beam;

Step 4: Excavate the foundation pit

After the roof beam and roof plate reach the design strength, according to the actual situation of the project, excavation shall be carried out layer by layer to the bottom of the foundation pit, and the grading slope, construction drainage ditch, foundation floor, and support belt shall be corrected;

Step Five: Construction of Recyclable Anchor

The recyclable anchor rod is anchored in the soil layer through the steps of manufacturing, drilling, hole forming, grouting, and tension locking. It can limit the lateral displacement of the inclined pile and the surrounding protection pile while strengthening the rock mass, and act as a tie rod. At the same time Test the horizontal displacement of the foundation pit, if it exceeds the value, add prestress;

Step 6: Remove the exposed inclined piles, top plate, and recoverable anchor rods

After the construction of the floor structure is completed, the exposed inclined piles and the top plate are removed, and the recyclable anchor rods are pulled out for recycling to reduce environmental pollution.

Compared with the prior art, the beneficial effects of the present invention are reflected in:

1. There is no horizontal internal support, which significantly reduces the project cost. The horizontal load is borne by the inclined pile. Compared with the traditional vertical pile, the mechanical performance of the pile body is greatly improved, and the arrangement of the inclined pile is more flexible, which increases the circumference of the foundation pit. The ability of the protective structure to control deformation.

2. Set up a soil reinforcement area at the bottom of the inclined pile to improve the properties of the soft soil, reduce the lateral displacement after the inclined pile is driven in, and improve the lateral bearing capacity of the inclined pile.

3. Actively use the tension of the recyclable anchor rod to share the lateral pressure acting on the inclined pile, which can limit the lateral displacement of the inclined pile, reduce the stress on the soil reinforcement area at the root of the inclined pile, and play the role of a tie rod; if the deformation is large Large, prestress can also be applied.

4. The recyclable anchor rods can be recycled after the construction of the base plate to reduce the pollution caused by the long-term existence of steel strands underground.

5. Compared with the traditional enclosure structure, the present invention has the advantages of strong ability to control deformation, low engineering cost, environmental friendliness and convenient construction.

Description of drawings

Fig. 1 is a sectional view of a combined enclosure structure for a soft soil foundation pit of the present invention;

Fig. 2 is a top view of a combined enclosure structure for foundation pits on soft ground according to the present invention;

Fig. 3 is a cross-sectional view of the bottom plate after construction of a combined enclosure structure for foundation pits on soft soil according to the present invention.

Detailed ways

The specific implementation manners of the embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation manners described here are only used to illustrate and explain the embodiments of the present invention, and are not intended to limit the embodiments of the present invention.

It should be noted that the embodiments of the present invention and the features of the embodiments may be combined with each other under the condition of no conflict.

The present invention will be described in detail below in conjunction with exemplary embodiments with reference to the accompanying drawings.

With reference to Fig. 1, Fig. 2 and Fig. 3, a kind of combined enclosure structure for soft ground foundation pit of the present invention comprises:

Enclosure piles 3, a plurality of enclosure piles 3 are vertically inserted on the edge of the foundation pit for retaining soil and water stop; the centers of the pile tops are connected in a straight line, and each pile top is connected by a pressure beam 4; each enclosure The part where the pile 3 protrudes into the soil is provided with a first connection through hole connected with the recoverable anchor rod 2;

Inclined pile 1, installed on an incline, the bottom of the inclined pile 1 goes deep into the soil inside the foundation pit, the lower end is provided with a second connection through hole connected with the recoverable anchor rod 2, and the top is poured with a top plate 5, and the top plate 5 and the top beam 4 The fixed connection connects the enclosure pile 3, the inclined pile 1, the top plate 5 and the top beam 4 to form a combined enclosure structure;

The retrievable anchor rod 2 is arranged obliquely; one end of the retrievable anchor rod 2 is inserted obliquely through the first connecting through hole and the second connecting through hole and then inserted into the soil outside the foundation pit to limit the inclined pile 1 Lateral displacement with the retaining pile 3;

The soil reinforcement area 6 is set around the bottom of the inclined pile 1 and is used to limit the displacement of the inclined pile 1 .

In one embodiment, the soil reinforcement area 6 is a cement mixing reinforcement formed at the bottom of the inclined pile 1 by means of high-pressure rotary spraying or forced grouting.

In an embodiment, the inclined piles 1 are prefabricated reinforced concrete pipe piles or I-shaped piles, and the angle between the inclined piles 1 and the vertical direction is between 20° and 60°; the inclined piles 1 are arranged at equal intervals. And they are parallel to each other, and the lower pile end penetrates into the soil layer below the pit bottom.

Specifically, when the inclined pile 1 connected to the top plate 5 described in the embodiment of the present invention has a large excavation depth and poor soil quality, it can be single or multiple, and can be single or double. Row.

In one embodiment, the surrounding protection piles 3 are vertical row piles, and the pile row adopts bored cast-in-place piles, SMW piles, prefabricated reinforced concrete I-shaped or section steel.

In an embodiment, the roofing beam 4 is a cast-in-situ strip structure, the roofing plate 5 is cast in-situ above the inclined pile 1 , the width of the roofing beam 4 is greater than the diameter of the enclosure pile 3 , and the width of the roofing plate 5 It is larger than the pile diameter of inclined pile 1.

In one embodiment, the soil reinforcement area adopts a grouting reinforcement method, a cement-soil mixing pile reinforcement method or a high-pressure rotary grouting reinforcement method.

The recyclable (prestressed) anchor rod 2 described in the embodiment of the present invention needs to be stretched multiple times according to the design to control the horizontal displacement at the purlin. For deeper foundation pits, the anchor rods can be laid in multiple layers according to the depth , by applying prestress in real time, the active control of the horizontal displacement around the foundation pit is realized.

Adopt the construction method of the combined enclosure structure described in the embodiment of the present invention, concrete construction steps are as follows:

Step 1: Construction of soil reinforcement area 6

Use grouting reinforcement method, cement-soil mixing pile reinforcement method or high-pressure rotary grouting reinforcement method to strengthen the soil in the design area, improve the shear strength of soft soil, reduce the lateral displacement after the inclined pile is driven, and improve the slope of the inclined pile. Anti-lateral bearing capacity;

Step 2: Construction of inclined pile 1 and enclosure pile 3

The inclined piles and vertical row piles are driven into the design area by static pressure method or high-pressure jet spraying method. The number, row number, angle and length of the inclined piles are determined according to the actual situation, and the vertical row piles are constructed to form enclosure piles;

Step 3: Construction of the top beam 4 and the top plate 5

Excavate to the bottom of the design position of the roofing beam, construct the roofing beam of the enclosure pile and the roofing plate of the inclined pile, and pour the roofing beam and the roofing plate to realize the integration of the enclosure pile, the inclined pile, the roofing plate and the roofing beam;

Step 4: Excavate the foundation pit

After the roof beam and roof plate reach the design strength, according to the actual situation of the project, excavation shall be carried out layer by layer to the bottom of the foundation pit, and the grading slope, construction drainage ditch, foundation floor, and support belt shall be corrected;

Step Five: Construction of Recyclable Anchor 2

The recyclable anchor rod is anchored in the soil layer through the steps of manufacturing, drilling, hole forming, grouting, and tension locking. It can limit the lateral displacement of the inclined pile and the surrounding protection pile while strengthening the rock mass, and act as a tie rod. At the same time Test the horizontal displacement of the foundation pit, if it exceeds the value, add prestress;

Step 6: Remove the exposed inclined pile 1, the top plate 5, and the recyclable anchor 3

After the construction of the bottom plate structure is completed, the exposed inclined piles and the top pressing plate are removed, and the recyclable bolts are pulled out and recycled to reduce the pollution to the environment.

The invention can significantly reduce the engineering cost and reduce the occupation of the construction work space in the foundation pit; the horizontal load is borne by the inclined pile, and compared with the traditional vertical pile, the mechanical performance of the pile body is greatly improved. In addition, a soil reinforcement area is set at the bottom of the inclined pile to improve the properties of the soft soil. At the same time, the tensile force of the recyclable anchor rod is actively used to share the lateral pressure on the inclined pile, which can limit the lateral displacement of the inclined pile and reduce the soil at the root of the inclined pile. The force in the reinforced area of the body acts as a tie rod. If the deformation is large, prestress can also be applied. This enclosure system has a good effect on controlling the horizontal deformation of the foundation pit and reducing material consumption, and is basically not limited by the excavation depth. It has the advantages of safety, economy, and environmental protection in deep and large foundation pit projects in soft soil areas. .

Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention, those skilled in the art can make the above-mentioned The embodiments are subject to changes, modifications, substitutions and variations.

Claims (7)

1. The utility model provides a combination formula envelope for soft soil foundation pit which characterized in that includes:

the guard piles are vertically inserted at the edge of the foundation pit and used for retaining soil and stopping water; the centers of all pile tops are connected in a straight line, and all pile tops are connected through a capping beam; a first connecting through hole connected with a recoverable anchor rod is formed in the part, extending into the soil body, of each fender post;

the inclined piles are obliquely arranged, the bottoms of the inclined piles penetrate into soil on the inner side of the foundation pit, second connecting through holes connected with the recyclable anchor rods are formed in the lower ends of the inclined piles, a top pressing plate is poured on the top of the inclined piles, and the top pressing plate is fixedly connected with a top pressing beam to connect the enclosure piles, the inclined piles, the top pressing plate and the top pressing beam into a whole to form a combined enclosure structure;

the recoverable anchor rod is obliquely arranged; one end of the recoverable anchor rod penetrates through the first connecting through hole and the second connecting through hole in an inclined mode in sequence and then is inserted into soil on the outer side of the foundation pit, and the recoverable anchor rod is used for limiting lateral displacement of the inclined pile and the fender pile;

and the soil body reinforcing area is arranged around the bottom of the inclined pile and used for limiting the displacement of the inclined pile.

2. The combined type enclosure structure for the foundation pit of the soft soil foundation according to claim 1, wherein the soil body reinforcing area is a cement stirring reinforcing body formed at the bottom of the inclined pile by means of high-pressure rotary spraying or forced grouting.

3. The combined type enclosure structure for the foundation pit of the soft soil foundation according to claim 1, wherein the inclined pile is a prefabricated reinforced concrete pipe pile or an I-shaped pile, and the included angle between the inclined pile and the vertical direction is 20-60 degrees; the inclined piles are arranged at equal intervals and are parallel to each other, and the pile end at the lower end extends into a soil layer below the pit bottom.

4. The combined type enclosure structure for the foundation pit of the soft soil foundation according to claim 1, wherein the enclosure piles are vertical row piles, and the row piles adopt cast-in-situ bored piles, SMW construction method piles, prefabricated reinforced concrete I-shaped piles or profile steel.

5. The combined type enclosure structure for the foundation pit of the soft soil foundation according to claim 1, wherein the capping beam is a cast-in-situ bar structure, the capping plate is cast in situ above the inclined piles, the width of the capping beam is larger than the pile diameter of the enclosure piles, and the width of the capping plate is larger than the pile diameter of the inclined piles.

6. The combined type enclosure structure for the foundation pit of the soft soil foundation according to claim 1, wherein the soil body reinforcing area adopts a grouting reinforcing method, a cement soil mixing pile reinforcing method or a high-pressure jet grouting reinforcing method.

7. A construction method using a combined type envelope structure as claimed in any one of claims 1 to 6, characterized in that the concrete construction steps are as follows:

the method comprises the following steps: construction soil body reinforcing area

The soil body in the designed area is reinforced by adopting a grouting reinforcement method, a cement soil mixing pile reinforcement method or a high-pressure jet grouting reinforcement method, so that the shear strength of soft soil is improved, the lateral displacement generated after the inclined pile is driven in is reduced, and the lateral bearing capacity of the inclined pile is improved;

step two: construction inclined pile and fender pile

The inclined piles and the vertical row piles are driven into a design area through a static pressure method or a high-pressure jet grouting method, the number, the row number, the angle and the length of the inclined piles are determined according to actual conditions, and the vertical row piles are constructed to form fender piles;

step three: construction capping beam and capping plate

Excavating to the bottom of a design position of a capping beam, constructing the capping beam of the fender pile and a capping plate of the inclined pile, and integrally pouring the capping beam and the capping plate to integrate the fender pile, the inclined pile, the capping plate and the capping beam;

step four: excavation foundation pit

After the capping beam and the capping plate reach the design strength, excavating to the bottom of the foundation pit in a partitioned and layered manner according to the actual engineering situation, correcting the slope surface, the construction drainage ditch, the foundation bottom plate and the support belt;

step five: construction recoverable anchor rod

The recoverable anchor rod is anchored in a soil layer after the steps of manufacturing, drilling, hole forming, grouting, tensioning and locking, lateral displacement of the inclined pile and the fender pile is limited while a rock body is reinforced, the function of a pull rod is achieved, horizontal displacement of the foundation pit is tested, and if the horizontal displacement exceeds a certain value, prestress is applied;

step six: demolish and expose inclined pile, roof pressing board, recoverable stock

After the construction of the bottom plate structure is completed, the exposed inclined piles and the exposed top pressing plate are removed, and the recoverable anchor rods are pulled out and recovered, so that the pollution to the environment is reduced.

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