CN108239983B

CN108239983B - Construction method of deep foundation pit

Info

Publication number: CN108239983B
Application number: CN201810037576.3A
Authority: CN
Inventors: 戴德军; 程喜
Original assignee: Seventh Engineering Co Ltd of China Railway 19th Bureau Group Co Ltd
Current assignee: Guangzhou Engineering Co Ltd of China Railway 19 Bureau Group Co Ltd
Priority date: 2018-01-16
Filing date: 2018-01-16
Publication date: 2020-03-24
Anticipated expiration: 2038-01-16
Also published as: CN108239983A

Abstract

The invention provides a construction method of a deep foundation pit, which comprises the following steps: dividing a substrate of the deep foundation pit into a plurality of first areas and a plurality of second areas, wherein the first areas and the second areas are arranged at intervals, the width of each first area is three times that of each second area, each first area is divided into a third area, a fourth area and a fifth area which are equal in width, and the fourth area is located between the third area and the fifth area; carrying out excavation operation on the second area, and pouring concrete in the excavated second area for carrying out primary bottom sealing; carrying out excavation operation on the fourth area, and pouring concrete in the excavated fourth area for carrying out secondary bottom sealing; and carrying out excavation operation on the third area and the fifth area, and pouring concrete in the excavated third area and the fifth area for carrying out third bottom sealing. The construction method of the invention effectively solves the problem of insufficient length of the steel sheet pile, and has the advantages of high construction speed and low construction cost.

Description

Construction method of deep foundation pit

Technical Field

The invention relates to the technical field of underground engineering construction, in particular to a construction method of a deep foundation pit.

Background

The steel sheet pile is a kind of hot rolled (or cold bending) shaped steel with locking notch or jaw, before the foundation pit of bearing platform construction is excavated, the steel sheet pile is driven into the ground, and the locking notches or jaws between adjacent steel sheet piles are mutually connected and occluded to form continuous steel sheet pile enclosure wall for retaining soil and water. The steel sheet pile is generally suitable for the foundation ditch engineering that the excavation degree of depth is not more than 7 meters, and to the deep foundation ditch that the foundation ditch degree of depth reaches more than 10 meters, current steel sheet pile can't satisfy the requirement. The length requirement of deep basal pit is satisfied through refuting two steel sheet piles to current way general, but the shortcoming through the mode of refuting is: the material waste is great, the field transportation cost is increased, the strength of the connected steel sheet pile is reduced, the deformation is easy to occur, and the construction cost of the deep foundation pit is greatly increased.

Disclosure of Invention

The invention aims to provide a construction method of a deep foundation pit with high efficiency and low cost.

In order to achieve the above object, the present invention provides a construction method of a deep foundation pit, comprising the steps of: determining an inserting and driving area of the steel sheet piles according to the length and the width of the deep foundation pit, punching the inserting and driving area, inserting and driving the steel sheet piles in the punched inserting and driving area, carrying out soil excavation operation on the area enclosed by the steel sheet piles to form the deep foundation pit, enclosing purlins are arranged between the steel sheet piles which are opposite to each other for reinforcement; dividing the substrate of the deep foundation pit into a plurality of first areas and a plurality of second areas along the length direction of the deep foundation pit, wherein the first areas and the second areas are arranged at intervals, the width of each first area is three times that of the second area, each first area is divided into a third area, a fourth area and a fifth area which are equal in width along the length direction, and the fourth area is located between the third area and the fifth area; carrying out excavation operation on the second area, and pouring concrete in the excavated second area for primary bottom sealing after all the second areas are excavated; carrying out excavation operation on the fourth area, and pouring concrete in the excavated fourth area for secondary bottom sealing after all the fourth areas are excavated; and carrying out excavation operation on the third area and the fifth area, and pouring concrete in the excavated third area and the fifth area for carrying out third bottom sealing after all the third area and the fifth area are excavated.

The further proposal is that the thickness of the concrete for the first bottom sealing is 1 m.

The further proposal is that the thickness of the concrete for the second bottom sealing is 1 m.

The further proposal is that the thickness of the concrete for the third bottom sealing is 1 m.

Further, the widths of the second region, the third region, the fourth region and the fifth region are all 1 m.

Further, the steel sheet pile adopts Larsen IV type steel sheet pile with length of 12 m.

The invention has the beneficial effects that: the foundation is divided into the second area, the third area, the fourth area and the fifth area which are equal in width, then the second area, the fourth area, the third area and the fifth area are sequentially dug and bottom sealing is poured, and by the method for excavating and pouring the bottom sealing at intervals, the back-gushing of soil bodies around the bottom of the steel sheet pile under pressure in the soil excavating process can be effectively prevented, meanwhile, mutual influence between the adjacent bottom sealing is avoided, and the speed of bottom sealing is high. The construction method of the invention has the advantages of high construction speed and low construction cost.

Drawings

Fig. 1 is a schematic structural diagram of an embodiment of a deep foundation pit of the present invention.

Fig. 2 is a schematic structural diagram of the substrate of the deep foundation pit embodiment of the present invention in a first state.

Fig. 3 is a schematic structural diagram of the substrate of the deep foundation pit embodiment of the invention in a second state.

Fig. 4 is a schematic structural diagram of the substrate of the deep foundation pit embodiment of the invention in a third state.

Fig. 5 is a schematic structural diagram of the substrate of the deep foundation pit embodiment of the invention in a fourth state.

Fig. 6 is a schematic structural diagram of the substrate of the deep foundation pit embodiment of the invention in a fifth state.

Fig. 7 is a schematic structural diagram of the substrate of the deep foundation pit embodiment of the invention in a sixth state.

The invention is further explained with reference to the drawings and the embodiments.

Detailed Description

In the embodiment of the invention, the depth of the main pier deep foundation pit reaches 10.5m and the length is 42m, if the most commonly used Larsen IV-type steel plate pile with the length of 12m is used as the enclosure wall, the effects of retaining soil and water cannot be realized by adopting the traditional method, and the method of alternately excavating and pouring the bottom seal effectively solves the problem of insufficient length of the steel plate pile, greatly improves the construction speed and reduces the cost.

Referring to fig. 1, fig. 1 is a schematic structural diagram of an embodiment of a deep foundation pit of the present invention. In this embodiment, the depth H1 of the deep foundation pit 1 is 10.5m, the length H2 of the steel sheet pile 2 is 12m, the concrete bottom sealing layer 10 is provided at the bottom of the deep foundation pit 1, and the construction of the main pier is performed on the surface of the concrete bottom sealing layer 10. Before the deep foundation pit 1 is excavated, an annular intercepting ditch 3 is excavated at the periphery of the deep foundation pit 1 to prevent water above the ground from entering the deep foundation pit 1. After the intercepting ditch 3 is dug, an inserting and punching area of the steel sheet pile 2 is determined according to the length and the width of the deep foundation pit 1, and then a hole is punched on the inserting and punching area by using a hole leading machine, wherein the hole is punched for the purpose of facilitating the insertion of the steel sheet pile 2 into the ground. And then, in the punched inserting and driving area, the steel sheet piles 2 are driven into the ground by using a pile driver, and locking notches between the adjacent steel sheet piles 2 are mutually connected and occluded to form the continuous steel sheet pile enclosure wall. The region that encloses steel sheet pile 2 is excavated earth and is operated, forms deep basal pit 1, and steel sheet pile 2 encloses into the perisporium of deep basal pit 1, sets up between just right steel sheet pile 2 and encloses purlin 4 and consolidate, improves steel sheet pile 2's stability. After the construction steps are completed, the foundation 11 of the deep foundation pit 1 is constructed by excavating at intervals and pouring a back cover, and the specific construction steps are shown in fig. 2 to 7.

Referring to fig. 2, fig. 2 is a schematic structural view of a substrate of an embodiment of a deep foundation pit of the present invention in a first state. In the present embodiment, only one of the sections of the substrate 11 is taken as an example for description, the length of the substrate 11 is 42m, and the length L of one of the sections shown in fig. 2 is 14 m. The substrate 11 is divided into a plurality of first regions 110 and a plurality of second regions 120 along the length direction of the deep foundation pit 1 (i.e., the X-axis direction shown in fig. 2), the first regions 110 and the second regions 120 are arranged at intervals, the width L1 of the first regions 110 is 3m, and the width L2 of the second regions 120 is 1 m. Each first region 110 is further divided into a third region 111, a fourth region 112 and a fifth region 113 of equal width along the length direction, and the fourth region 112 is located between the third region 111 and the fifth region 113. All of the second regions 120 are then excavated to form trenches in the second regions 120.

Referring to fig. 3, fig. 3 is a schematic structural view of the substrate of the deep foundation pit embodiment of the present invention in a second state. After all the second areas 120 are excavated, concrete is poured into the grooves of the second areas 120, the substrate 11 is subjected to primary bottom sealing, concrete layers 1200 are formed in the substrate 11 at intervals, and the thickness of the concrete layers 1200 is 1 m.

Referring to fig. 4, fig. 4 is a schematic structural view of the substrate of the deep foundation pit embodiment of the present invention in a third state. After the concrete is poured into the grooves of the second area 120, all the fourth areas 112 are excavated to form the grooves in the fourth areas 112.

Referring to fig. 5, fig. 5 is a schematic structural view of the substrate of the deep foundation pit embodiment of the present invention in a fourth state. After all the fourth areas 112 are excavated, concrete is poured into the grooves of the fourth areas 112, the substrate 11 is subjected to bottom sealing for the second time, concrete layers 1120 are formed in the substrate 11 at intervals, and the thickness of the concrete layers 1120 is 1 m.

Referring to fig. 6, fig. 6 is a schematic structural view of the substrate of the deep foundation pit embodiment of the present invention in a fifth state. After the concrete is poured into the grooves of the fourth region 112, all of the third region 111 and the fifth region 113 are subjected to excavation work, and grooves are formed in the third region 111 and the fifth region 113.

Referring to fig. 7, fig. 7 is a schematic structural view of the substrate of the deep foundation pit embodiment of the present invention in a sixth state. After all the third area 111 and the fifth area 113 are excavated, concrete is poured into the grooves of the third area 111 and the fifth area 113, the substrate 11 is subjected to bottom sealing for the third time,

concrete layers

1110 and 1130 are formed in the substrate 11 at intervals, and the thickness of the

concrete layers

1110 and 1130 is 1 m.

The concrete bottom sealing layer 10 (see fig. 1) with the thickness of 1m is formed on the surface of the substrate 11 through the method, water and sand are prevented from flowing back into the deep foundation pit 1 through the bottom of the steel sheet pile 2, meanwhile, the concrete bottom sealing layer 10 improves the supporting strength of the substrate 11, and the main pier poured on the concrete bottom sealing layer 10 is more stable and is not easy to collapse. Through the mode of the interval excavation, the reverse surge of the soil body on the periphery of the bottom of the steel sheet pile 2 under the pressure in the process of excavating the groove is effectively prevented. The mode of excavating the back covers at intervals avoids the mutual influence between the adjacent back covers, and the speed of the back covers is high.

Of course, the above embodiments are only preferred embodiments of the present invention, and there may be more variations in practical applications, for example, the thickness of the back cover may be more than 1 m; any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A construction method of a deep foundation pit is characterized in that:

determining an inserting and driving area of a steel sheet pile according to the length and the width of the deep foundation pit, punching the inserting and driving area, inserting and driving the steel sheet pile in the punched inserting and driving area, excavating soil in the area enclosed by the steel sheet pile to form the deep foundation pit, enclosing the steel sheet pile into the peripheral wall of the deep foundation pit, and arranging an enclosing purlin between the steel sheet piles which are opposite to each other for reinforcement;

dividing a base of a deep foundation pit into a plurality of first areas and a plurality of second areas along the length direction of the deep foundation pit, wherein the first areas and the second areas are arranged at intervals, the width of each first area is three times that of each second area, each first area is divided into a third area, a fourth area and a fifth area which are equal in width along the length direction, and the fourth area is located between the third area and the fifth area;

carrying out excavation operation on the second area, and pouring concrete in the excavated second area for primary bottom sealing after all the second area is excavated;

carrying out excavation operation on the fourth area, and pouring concrete in the excavated fourth area for secondary bottom sealing after all the fourth area is excavated;

and carrying out excavation operation on the third area and the fifth area, and pouring concrete in the excavated third area and the fifth area for carrying out third bottom sealing after all the third area and the fifth area are excavated.

2. The construction method of the deep foundation pit according to claim 1, wherein:

the thickness of the concrete of the first back cover is 1 m.

3. The construction method of the deep foundation pit according to claim 1, wherein:

the thickness of the concrete of the second back cover is 1 m.

4. The construction method of the deep foundation pit according to claim 1, wherein:

the thickness of the concrete of the third back cover is 1 m.

5. The construction method of the deep foundation pit according to claim 1, wherein:

the widths of the second, third, fourth and fifth regions are all 1 m.

6. A construction method of a deep foundation pit according to any one of claims 1 to 5, wherein:

the steel sheet pile is a Larsen IV type steel sheet pile with the length of 12 m.