CN110952559A

CN110952559A - Narrow and long open caisson in thick and soft soil layer and construction method thereof

Info

Publication number: CN110952559A
Application number: CN201911289147.6A
Authority: CN
Inventors: 邱庚鸿; 何德华; 陈建宁; 黄金铭; 袁程; 郭一贤; 曹钰; 邹嘉威
Original assignee: Guangzhou Third Municipal Engineering Co Ltd
Current assignee: Guangzhou Third Municipal Engineering Co Ltd
Priority date: 2019-12-13
Filing date: 2019-12-13
Publication date: 2020-04-03

Abstract

The invention provides a narrow and long open caisson in a thick soft soil layer and a construction method thereof, which relate to the technical field of open caisson construction, wherein the open caisson is formed by splicing a plurality of segments, and the method comprises the following steps: step 1, setting a sunk well position, and arranging cement mixing piles in a soil layer at the sunk well position to reinforce the soil layer; step 2, manufacturing a first segment above the soil layer; step 3, draining and excavating soil in the well area until the sections descend to a preset distance away from the ground; step 4, manufacturing the next segment on the manufactured segment in an alignment manner; step 5, draining and excavating soil in the well region until the next segment descends to a preset distance away from the ground; step 6, repeating the steps 4-5 until all the segments are manufactured; and 7, grouting the bottom of the open caisson and sealing the bottom. The invention can prevent the phenomena of pit bottom uplift, sinking of soil layers around the open caisson and the like caused by overlarge water pressure in the open caisson in the sinking process.

Description

Narrow and long open caisson in thick and soft soil layer and construction method thereof

Technical Field

The invention relates to the technical field of open caisson construction, in particular to a narrow and long open caisson in a thick soft soil layer and a construction method thereof.

Background

The thick soft soil layer has the characteristics of high natural water content, low strength, easy uplift of pit bottom, quicksand repacking and the like, and is difficult to carry out open caisson construction. In Chen Guozi 'soft soil foundation open caisson sinking construction technology and application', an open caisson construction mode is provided, heavy well point dewatering is adopted as an auxiliary process, and silt is consolidated while the underground water level is lowered so as to ensure that consolidated soil quality can meet the requirement of open caisson sinking.

However, it is difficult to ensure the stability of the large open caisson when it is sunk, and the open caisson may be inclined due to the soft soil when it is sunk.

Disclosure of Invention

In view of the above technical problems, the present invention aims to provide a long and narrow caisson capable of ensuring a stable sinking of a thick and soft soil layer and a construction method thereof.

In order to solve the technical problem, the embodiment of the invention adopts the following technical scheme to realize:

the invention provides a construction method of a narrow and long open caisson in a thick and soft soil layer, wherein the open caisson is formed by splicing a plurality of segments, and the method comprises the following steps:

step 1, setting a sunk well position, and arranging cement mixing piles in a soil layer at the sunk well position to reinforce the soil layer;

step 2, manufacturing a first segment above the soil layer;

step 3, draining and excavating soil in the well area until the sections descend to a preset distance away from the ground;

step 4, manufacturing the next segment on the manufactured segment in an alignment manner;

step 5, draining and excavating soil in the well region until the next segment descends to a preset distance away from the ground;

step 6, repeating the steps 4-5 until all the segments are manufactured;

and 7, grouting the bottom of the open caisson and sealing the bottom.

Advantageously or exemplarily, in step 1, the soil layer at the open caisson location comprises: the soil layer of the inner area of the open caisson and the soil layer of the peripheral area of the open caisson.

Advantageously or exemplarily, the method further comprises, after step 2, making a tang portion on the lower end face of the first segment; the method further comprises the following steps: and manufacturing a support beam at the lower part of the first section close to the blade foot part, wherein two ends of the support beam are respectively connected to two sides of the first section, and the support beam is made of reinforced concrete.

Advantageously or exemplarily, in step 7, the slurry is injected to the height of the upper end surface of the support beam.

Advantageously or exemplarily, the step 2 and the step 4, the making of the first segment and the making of the next segment comprise: fabricating a support structure within a segment, the support structure for structurally stabilizing the segment; and 7, after the bottom sealing is finished, removing the supporting structure.

Advantageously or exemplarily, the segment is a hollow cuboid comprising opposite first and second sides and opposite third and fourth sides, the first and second sides having a length greater than that of the third and fourth sides, and steps 3 and 5 include:

and S1, digging from the center of the well area to the joint between the first side, the second side, the third side and the fourth side simultaneously to form a downward sunken pot bottom.

And S2, excavating from the center of the well area to the third side and the fourth side simultaneously, wherein the excavation depth is the depth of the center of the bottom of the boiler.

And S3, excavating from the joints of the first, second, third and fourth sides to the middle points of the first and second sides at the same time, wherein the excavating depth is the depth of the center of the pot bottom.

Advantageously or exemplarily, in step 3, the process loops S1-S3 until the segment sinks to a preset distance from the ground; in step 5, loop S1-S3 until the next segment sinks a preset distance from the ground.

Advantageously or exemplarily, the step 3 and the step 5 comprise calculating the inclination angle of the bottom surface of the open caisson, and correcting the inclination when the bottom surface inclines to one side and the inclination angle is larger than the maximum allowable inclination angle; setting the open caisson region corresponding to the lower end of the inclined bottom surface as a first region, and setting the open caisson region corresponding to the upper end of the inclined bottom surface as a second region, wherein the correcting the inclination comprises:

and backfilling a soil layer in the first area, and excavating the soil layer in the second area until the inclination angle of the bottom surface is smaller than the maximum allowable inclination angle.

Advantageously or exemplarily, the correcting the tilt further comprises:

and after the inclination angle of the bottom surface is smaller than the maximum allowable inclination angle, continuously excavating the soil layer in the second area until the bottom surface inclines towards the other side opposite to the one side, resetting the first area and the second area, backfilling the soil layer in the reset first area, and excavating the soil layer in the reset second area until the inclination angle of the bottom surface is 0.

The invention provides a narrow and long open caisson in a thick and soft soil layer, which is manufactured by the construction method.

The various embodiments of the invention have the following beneficial effects:

1. the invention is suitable for open caisson construction at a thick soft soil layer, before installing the open caisson, cement paste mixing piles are firstly manufactured at the position of the open caisson to reinforce the soil layer, so that the phenomena of pit bottom uplift, open caisson surrounding soil layer sinking and the like caused by overlarge water pressure in the open caisson in the sinking process are prevented; simultaneously, the cement mixing pile can also make the open caisson sink and do not take place off normal or slope, can make the open caisson accurately sink to the elevation of designing requirement.

2. The cement mixing piles are arranged in the inner region and the outer region of the open caisson position, and the cement mixing piles arranged in the outer region of the open caisson can reduce active soil pressure borne by the open caisson; the soil layer can be consolidated to the cement stirring stake of regional setting in the open caisson, improves soil layer intensity and lateral resistance, reduces the displacement of open caisson, prevents in the open caisson soil layer uplift destruction and seepage flow destruction.

3. The invention is provided with the narrow and long open caisson, has large bearing area, allows larger embedding depth, can bear larger vertical load and horizontal load, and can meet the construction requirement in soft soil.

4. The supporting structure is dismantled after the bottom sealing is finished, and the subsequent construction is not influenced.

Drawings

The invention is further illustrated by means of the attached drawings, but the embodiments in the drawings do not constitute any limitation to the invention, and for a person skilled in the art, other drawings can be obtained on the basis of the following drawings without inventive effort.

Fig. 1 is a top view of a long and narrow caisson section for a thick soft soil layer according to an exemplary embodiment of the present invention;

fig. 2 is a sectional view in a-a direction of fig. 1 of a long and narrow caisson section in a thick soft soil layer according to an exemplary embodiment of the present invention;

fig. 3 is a B-B direction sectional view of the long and narrow caisson section of a thick soft soil layer according to an exemplary embodiment of the present invention;

fig. 4 is an installation sectional view of a long and narrow caisson in a thick soft soil layer according to an exemplary embodiment of the present invention;

fig. 5 is a C-C sectional view of the long and narrow caisson in a thick soft soil layer according to an exemplary embodiment of the present invention;

fig. 6 is a flow chart of a construction method of a long and narrow open caisson in a thick and soft soil layer according to an exemplary embodiment of the present invention;

fig. 7 is a first excavation direction diagram of a narrow and long open caisson construction method for a thick and soft soil layer according to an exemplary embodiment of the present invention;

fig. 8 is a second excavation direction diagram of a narrow and long open caisson construction method for a thick and soft soil layer according to an exemplary embodiment of the present invention;

fig. 9 is a first state diagram of inclination correction of a long and narrow caisson in a thick soft soil layer according to an exemplary embodiment of the present invention;

fig. 10 is a second state diagram of inclination correction of a long and narrow caisson in a thick soft soil layer according to an exemplary embodiment of the present invention;

fig. 11 is a third state diagram of inclination correction of a long and narrow caisson in a thick soft soil layer according to an exemplary embodiment of the present invention;

fig. 12 is a fourth state diagram of inclination correction of a long and narrow caisson in a thick soft soil layer according to an exemplary embodiment of the present invention.

Reference numerals: 1-segment; 21-a first side; 22-a second side; 31-a third side; 32-a fourth side; 4-a blade foot portion; 5-a support beam; 6-inner partition wall; 7-steel pipe group; 8-a concrete column; 9-base.

Detailed Description

The invention is further described below with reference to the following examples in conjunction with the accompanying drawings.

The embodiment of the first aspect of the present invention provides a support structure, as shown in fig. 1 to 5, for supporting a long and narrow caisson segment 1 of a thick soft soil layer, wherein the segment 1 is a hollow cuboid, and comprises a first side 21 and a second side 22 which are opposite, and a third side 31 and a fourth side 32 which are opposite, and the lengths of the first side 21 and the second side 22 are greater than the lengths of the third side 31 and the fourth side 32.

The support structure is detachably connected to the segment 1, and comprises: a first support member vertically abutted between the first side surface 21 and the second side surface 22; and two ends of the second supporting piece are respectively abutted against the two adjacent side faces.

Wherein the first support piece counteracts the acting force of the soft soil on the first and

second side surfaces

31 and 32, and the second support piece counteracts the acting force of the soft soil on the vertical connection part of the adjacent side surfaces; the stress of the open caisson segment 1 is more uniform when the open caisson segment sinks, the pressure of soft soil on the segment 1 in the sinking process is effectively offset, and the sinking stability is improved.

In another embodiment, the first support is not vertically abutted between the first side 21 and the second side 22, but vertically abutted between the third side 31 and the fourth side 32. In another embodiment, the first support is arranged to abut perpendicularly between said first 21 and second 22 sides and between said third 31 and fourth 32 sides. The first support member is arranged between the third side surface 31 and the fourth side surface 32, so that the pressure of soft soil on the third side surface 31 and the fourth side surface 32 can be buffered, and the sinking stability can be further increased.

In one embodiment, when the first support is disposed between the third side 31 and the fourth side 32, the lengths of the first and

second sides

21,22 and the third and

fourth sides

31,32 are similar, such as a ratio of 1-2: 1.

In another embodiment, when the lengths of the first and second side surfaces 21,22 are different from the lengths of the third and fourth side surfaces 31,32, such as a ratio of 10-18: 3, the first support member 2 is only disposed between the first and second side surfaces 21,22 for obtaining a better support effect within a limited cost.

Wherein, the proportion of the first, second, third and fourth sides is determined according to the site construction, in one embodiment, the proportion of the first and

second sides

21,22 to the third and

fourth sides

31,32 is 10:3, the length of the first and

second sides

21,22 is 40m, and the length of the third and

fourth sides

31,32 is 12 m; in another embodiment, the ratio of the first and

second sides

21,22 to the third and

fourth sides

31,32 is 18:3, the length of the first and

second sides

21,22 is 74m, and the length of the third and

fourth sides

31,32 is 12 m.

In a preferred embodiment, the first supporting member is only disposed between the first and second opposite side surfaces 21,22, which can reduce the cost, and the second supporting member supports the third and fourth side surfaces 31,32 with shorter length, and the supporting effect is not greatly affected by the absence of the first supporting member between the third and fourth side surfaces 31, 32.

In one embodiment, the segments 1 may be circular segments 1, with the support structure being provided between the inner walls of the circular segments 1.

In one embodiment, the method further comprises: an inner partition wall 6, the inner partition wall 6 being parallel to the first support. In a preferred embodiment, when the first supporting members are only arranged on the first and second lateral surfaces 21,22, one inner partition wall 6 is arranged to divide the segment 1 into two uniform left and right parts, i.e. the inner partition wall 6 is arranged at the midpoint of the first and second lateral surfaces 21,22, and the preferred embodiment can play a better supporting role. In another embodiment, the inner partition wall 6 may be provided in plurality.

In one embodiment, the first support comprises a steel tube set 7; the steel tube assembly 7 comprises a plurality of steel tubes, which in one embodiment are evenly distributed from left to right, and the two ends of the steel tubes are connected to the first and

second sides

21,22, respectively. In a further embodiment, two sets of steel pipes 7 are provided, which are respectively provided on the upper and middle portions of the first and second side surfaces 21,22 from top to bottom.

In one embodiment, the steel tube group 7 is provided with both the inner partition wall 6 and the first support member to obtain the maximum supporting effect.

In one embodiment, the second support member comprises a plurality of concrete columns 8, and the concrete columns 8 are provided in plurality and are sequentially arranged on two adjacent sides from top to bottom.

Due to the arrangement of the concrete columns 8, the relative relation between two adjacent side faces cannot be changed in the sinking process, and the two side faces are always kept in a mutually perpendicular state.

The supporting structure that sets up in this embodiment makes open caisson festival section atress more even when sinking, effectively offsets the pressure of the in-process weak soil of sinking to the festival section, increases the stability of sinking.

In a second aspect, the embodiment of the invention provides a narrow and long caisson in a thick and soft soil layer, as shown in fig. 1-5, the caisson is formed by splicing a plurality of caisson sections 1, the support structure is arranged in each section 1, and a base 9 formed by pouring is arranged at an opening at the lower end of each section 1 at the bottom.

In one embodiment, a cutting edge portion 4 is provided at the lower end surface of the bottom section 1, and a plurality of support beams 5 are further included, the support beams 5 are provided at the lower portions of the first side surface 21 and the second side surface 22 near the cutting edge portion 4, and the support beams 5 vertically abut between the first side surface 21 and the second side surface 22.

Because the supporting structure is detachably connected with the segment 1, the inner partition wall 6, the steel pipe and the concrete column 8 are detachably connected with the segment 1. In one embodiment, the detachable connection is a concrete pour, and upon detachment, the concrete pour connection is chiseled or broken.

The embodiment is provided with the narrow and long open caisson, so that the bearing area is large, the larger embedding depth is allowed, the larger vertical load and the larger horizontal load can be borne, and the construction requirement in soft soil can be met.

In a third aspect of the present invention, there is provided a method for constructing a long and narrow caisson in a thick and soft soil layer, for manufacturing the above caisson, as shown in fig. 6, the method includes the following steps:

step 1, setting a sunk well position, and arranging cement mixing piles in a soil layer at the sunk well position to reinforce the soil layer. In one embodiment, in step 1, the soil layer at the open caisson location comprises: the soil layer of the inner area of the open caisson and the soil layer of the peripheral area of the open caisson.

The setting method of the cement mixing pile comprises the following steps: arranging a drilling machine on a soil layer at the open caisson position, wherein the drilling machine rotates forwards, and a drill bit drills to a preset depth; and opening the grouting pump and simultaneously reversely rotating the drilling machine, and lifting the drill bit to the ground surface. And in the process of lifting the drill bit, a grouting pump performs grouting in the hole to form the cement mixing pile.

In one embodiment, in the soil layer in the inner region of the open caisson, the cement mixing piles are grid type cement mixing piles with the D800@ 600; in the soil layer of the peripheral area of the open caisson, the cement mixing piles are double-row cement mixing piles with the diameter D800@ 600.

In the embodiment, cement mixing piles are arranged in the inner area and the outer area of the open caisson position, and the cement mixing piles arranged in the outer area of the open caisson can reduce the active soil pressure borne by the open caisson; the soil layer can be consolidated to the cement stirring stake of regional setting in the open caisson, improves soil layer intensity and lateral resistance, reduces the displacement of open caisson, prevents in the open caisson soil layer uplift destruction and seepage flow destruction.

Step 2, a first segment 1 is manufactured above the soil layer.

One method of making the first segment 1 is as follows: and (3) setting an outer die and an inner die at a preset open caisson position, grouting an area enclosed by the outer die and the inner die, and forming the section 1. Another method for manufacturing the first segment 1 is to use an assembled open caisson to hoist the prefabricated segment 1 to the open caisson position.

In one embodiment, the method further comprises, after step 2, making a tang portion 4 on the lower end face of the first segment 1; the method further comprises the following steps: after the step 2, a support beam 5 is manufactured at the lower part of the first section 1 close to the cutting edge part 4, two ends of the support beam 5 are respectively connected to two sides of the first section 1, and the support beam 5 is made of reinforced concrete.

And 3, draining and excavating soil in the well area until the segment 1 descends to a preset distance away from the ground.

Wherein the preset distance is more than 1m and is determined by the actual construction environment.

In one embodiment, before step 1, calculating the size of the open caisson and the segment 1 thereof according to the site construction requirements, and carrying out construction preparation and measurement setting-out at the open caisson position so as to facilitate the manufacture of the cement mixing pile; before step 2, guiding and bedding construction is carried out at the open caisson position, the guiding and bedding are dismantled before the first section 1 is manufactured, namely step 3, and the guiding and bedding construction comprises manufacturing of templates and reinforcing steel bars and leveling of the installation position.

And 4, aligning and manufacturing the next segment 1 on the manufactured segment 1.

The method of making the next segment 1 is similar to the method of making the first segment 1. The method for manufacturing the next segment 1 in alignment comprises the following steps: and arranging an inner die and an outer die on the upper end surface of the manufactured segment 1, and grouting the area enclosed by the inner die and the outer die to form the segment 1. Another method for manufacturing the next segment 1 in the alignment mode is to adopt an assembled open caisson to hoist the prefabricated next segment 1 to the manufactured segment 1.

And 5, draining and excavating soil in the well region until the next segment 1 descends to a preset distance away from the ground.

And 6, repeating the steps 4-5 until all the segments 1 are manufactured.

And 7, grouting the bottom of the open caisson and sealing the bottom. In one embodiment, in step 7, the slurry is injected to the height of the upper end surface of the support beam.

In one embodiment, steps 2 and 4, the making of the first segment 1 and the making of the next segment 1 comprise: the above-described support structure is made in the segment 1, which support structure serves to keep the segment 1 structurally stable. In one embodiment, in step 7, the slurry is poured to a distance from the lower end surface of the support beam, and after the bottom sealing is finished, the support beam is chiseled. And 7, after the bottom sealing is finished, removing the supporting structure.

In one embodiment, the segment 1 is a hollow cuboid comprising first and second

opposite sides

21,22 and third and fourth

opposite sides

31,32, the first and

second sides

21,22 having a length greater than the third and

fourth sides

31,32, and the steps 3 and 5 include:

and S1, digging from the center of the well area to the joints among the first, second, third and

fourth sides

21,22,31 and 32 to form a pot bottom which is concave downwards.

And S2, excavating towards the third side surface 31 and the fourth side surface 32 from the center of the well area, wherein the excavating depth is the central depth of the bottom of the boiler, and the excavating direction is shown in figure 7.

S3, excavating towards the middle points of the first side surface 21 and the second side surface 22 from the connecting positions of the first side surface 21, the second side surface 21, the third side surface 21 and the fourth side surface 22, wherein the excavating depth is the depth of the center of the pot bottom, and the excavating direction is shown in figure 8.

The embodiment provides a feasible underground region soil-excavating sinking mode, the bottom of a pan is excavated from the center, then the pan is excavated towards the third and the fourth side surfaces 31 and 32 as the short sides, and finally the pan is excavated from the joints of the four corners towards the middle points of the first and the second side surfaces 21 and 22 as the long sides, so that the sunk well can be guaranteed to sink uniformly and slowly.

In the above embodiment, the sinking speed of the first segment 1 is not more than 0.5m for one day, the height difference of the end surface of the uppermost segment 1 is not more than 0.3m during the sinking process, and the depth of the center of the bottom of the pan is 1.5 m.

In one embodiment, the excavation depth of S2 and S3 is not equal to the pan bottom center depth, and S2 and S3 are repeated a plurality of times until the open caisson region is level with the pan bottom center depth. In one embodiment, the excavation depth of S2 and S3 is 0.5 m.

In one embodiment, in step 3, loop S1-S3 until the segment sinks a preset distance from the ground; in step 5, loop S1-S3 until the next segment sinks a preset distance from the ground.

In the sinking process, because instability exists in the actual excavation process, the open caisson cannot be guaranteed to be always kept horizontal, and the open caisson can sink unevenly, the actual axis P2 deviates from the design axis P1, and in a serious condition, the open caisson can be inclined greatly to influence the quality of the open caisson.

In one embodiment, as shown in fig. 9-12, step 3 and step 5 include calculating the inclination angle of the bottom surface of the open caisson, and correcting the inclination when the bottom surface is inclined to one side and the inclination angle is larger than the maximum allowable inclination angle, as shown in fig. 9; setting the open caisson region corresponding to the lower end of the inclined bottom surface as a first region, and setting the open caisson region corresponding to the upper end of the inclined bottom surface as a second region, wherein the correcting the inclination comprises:

In the embodiment, an eccentric excavation mode is adopted, a soil layer is backfilled towards the inclined lower end face, excavation is strengthened towards the inclined raised upper end face, and inclination can be effectively corrected.

In one embodiment, the inclination angle of the bottom surface is obtained by calculating the inclination angle of the upper end surface of the uppermost segment 1.

In one embodiment, the correcting for tilt further comprises: after the inclination angle of the bottom surface is smaller than the maximum allowable inclination angle, as shown in fig. 10, soil is excavated in the second area continuously until the bottom surface inclines towards the other side opposite to the one side, as shown in fig. 11, the first area and the second area are reset, the soil is backfilled in the reset first area, and the soil is excavated in the reset second area until the inclination angle of the bottom surface is 0, as shown in fig. 12.

In this embodiment, since the caisson is displaced by gravity after the inclination, the caisson still continues to excavate a soil layer in the originally set second area after the caisson is first restored to the vertical angle, and the caisson is inclined to the opposite side, so that the caisson is displaced by the opposite displacement under the action of gravity. This embodiment can offset the displacement that produces because the open caisson slope effectively, corrects the displacement simultaneously at the correction slope.

The construction method of the embodiment of the invention is suitable for open caisson construction at a thick and soft soil layer, before the open caisson is installed, cement paste mixing piles are firstly manufactured at the open caisson position to reinforce the soil layer, so that the phenomena of pit bottom uplift, open caisson surrounding soil layer sinking and the like caused by overlarge water pressure in the open caisson in the sinking process are prevented; simultaneously, the cement mixing pile can also make the open caisson sink and do not take place off normal or slope, can make the open caisson accurately sink to the elevation of designing requirement.

Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the protection scope of the present invention, although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A construction method of a narrow and long open caisson in a thick and soft soil layer is characterized in that the open caisson is formed by splicing a plurality of segments, and the method comprises the following steps:

step 2, manufacturing a first segment above the soil layer;

step 6, repeating the steps 4-5 until all the segments are manufactured;

and 7, grouting the bottom of the open caisson and sealing the bottom.

2. The construction method of the narrow and long open caisson in thick and soft soil layer as claimed in claim 1, wherein in step 1, the soil layer at the open caisson position comprises: the soil layer of the inner area of the open caisson and the soil layer of the peripheral area of the open caisson.

3. The method for constructing a long and narrow caisson in a thick and soft soil layer according to claim 1, further comprising, after step 2, forming a blade portion on the lower end surface of the first section; the method further comprises the following steps: and manufacturing a support beam at the lower part of the first section close to the blade foot part, wherein two ends of the support beam are respectively connected to two sides of the first section, and the support beam is made of reinforced concrete.

4. The method as claimed in claim 3, wherein the step 7 is performed by grouting to the height of the upper end surface of the support beam.

5. The construction method of the long and narrow open caisson in thick and soft soil as claimed in claim 1, wherein in the step 2 and the step 4, the step of making the first segment and the step of making the next segment comprises: fabricating a support structure within a segment, the support structure for structurally stabilizing the segment; and 7, after the bottom sealing is finished, removing the supporting structure.

6. The method as claimed in claim 1, wherein the segment is a hollow cuboid comprising opposite first and second sides and opposite third and fourth sides, the first and second sides having a length greater than that of the third and fourth sides,

in step 3 and step 5, the method comprises the following steps:

s1, digging from the center of the well area to the joint between the first, second, third and fourth sides to form a pot bottom sinking downwards,

s2, excavating from the center of the well area to the third and the fourth sides at the same time, wherein the excavating depth is the depth of the center of the bottom of the pan,

7. The construction method of long and narrow open caisson in a thick and soft soil layer as claimed in claim 6, wherein in step 3, repeating S1-S3 until said segments are sunk to a preset distance from the ground; in step 5, loop S1-S3 until the next segment sinks a preset distance from the ground.

8. The construction method of the long and narrow open caisson in a thick and soft soil layer as claimed in claim 1, wherein in step 3 and step 5, the inclination angle of the bottom surface of the open caisson is calculated, and when the bottom surface is inclined to one side and the inclination angle is larger than the maximum allowable inclination angle, the inclination is corrected;

setting the open caisson region corresponding to the lower end of the inclined bottom surface as a first region, and setting the open caisson region corresponding to the upper end of the inclined bottom surface as a second region, wherein the correcting the inclination comprises:

backfilling the soil layer in the first area, and/or excavating the soil layer in the second area until the inclination angle of the bottom surface is smaller than the maximum allowable inclination angle.

9. The construction method of the long and narrow open caisson in a thick and soft soil layer according to claim 8, wherein the correcting the inclination further comprises:

when the inclination angle of the bottom surface is smaller than the maximum allowable inclination angle, continuously excavating the soil layer in the second area until the bottom surface inclines towards the other side opposite to the one side,

resetting the first area and the second area,

and backfilling the soil layer in the reset first area, and excavating the soil layer in the reset second area until the inclination angle of the bottom surface is 0.

10. A long and narrow open caisson in thick and soft soil layer, which is manufactured by the construction method as claimed in any one of claims 1-9.