阅读说明：本技术 用于沿海的钢板桩、围堰及旋喷墙的组合结构及施工方法 (Combined structure of steel sheet pile, cofferdam and rotary spraying wall for coastal and construction method ) 是由 程保根 易文明 翟雪梅 陈世全 何富刚 于 2021-09-16 设计创作，主要内容包括：本发明公开了一种用于沿海的钢板桩、围堰及旋喷墙的组合结构,设置在沿海滩地上,所述沿海滩地包括透水层和位于所述透水层下方的不透水层,所述组合结构包括围堰及旋喷墙组件和双排钢板桩,围堰及旋喷墙组件设置在外海与基坑之间,双排钢板桩竖直设置在所述围堰及旋喷墙组件与所述基坑之间；所述双排钢板桩包括第一层钢板桩、第二层钢板桩、钢管支撑和砂土层,本发明通过设置在围堰及旋喷墙组件与基坑之间设置双排钢板桩,以跟挡水围堰、高压旋喷防渗墙形成组合结构,共同挡水及确保基坑稳定,克服了施工场地狭小、施工工期紧张、基础承载力低等困难,快速创造水闸干地施工的条件。(The invention discloses a combined structure of a steel sheet pile, a cofferdam and a rotary spraying wall for coastal areas, which is arranged on the coastal area, wherein the coastal beach area comprises a permeable layer and a impermeable layer positioned below the permeable layer, the combined structure comprises a cofferdam, a rotary spraying wall assembly and double-row steel sheet piles, the cofferdam and the rotary spraying wall assembly are arranged between the open sea and a foundation pit, and the double-row steel sheet piles are vertically arranged between the cofferdam, the rotary spraying wall assembly and the foundation pit; the double-row steel sheet pile comprises a first layer of steel sheet pile, a second layer of steel sheet pile, a steel pipe support and a sand layer, and the double-row steel sheet pile is arranged between the cofferdam and the rotary spraying wall assembly and the foundation pit to form a combined structure with the water retaining cofferdam and the high-pressure rotary spraying impervious wall, so that water is retained together, the stability of the foundation pit is ensured, the difficulties of narrow construction field, short construction period, low foundation bearing capacity and the like are overcome, and the condition of dry construction of the water gate is created quickly.)

1. A integrated configuration for steel sheet pile, cofferdam and rotary spray wall in coastal region, characterized in that, set up on the coastal beach, the coastal beach includes permeable bed and the impermeable bed that is located the permeable bed below, the integrated configuration includes:

the cofferdam and rotary spraying wall assembly is arranged between the open sea and the foundation pit;

the double rows of steel sheet piles are vertically arranged between the cofferdam and the rotary spraying wall assembly and the foundation pit;

double steel sheet pile includes:

the first layer of steel sheet piles are vertically arranged;

the second layer of steel sheet piles are arranged in parallel with the first layer of steel sheet piles, and gaps are formed between the first layer of steel sheet piles and the second layer of steel sheet piles;

the steel pipe support is arranged between the first layer of steel plate piles and the second layer of steel plate piles and is provided with a first end and a second end, the first end of the steel pipe support is fixedly connected with the first layer of steel plate piles, and the second end of the steel pipe support is fixedly connected with the second layer of steel plate piles;

and the sand layer is backfilled between the first layer of steel sheet piles and the second layer of steel sheet piles.

2. The combined structure of steel sheet piles, cofferdams and rotary spraying walls for coastal areas of claim 1, wherein the upper end surface of the first layer of steel sheet piles and the upper end surface of the second layer of steel sheet piles are located at the same horizontal plane, the steel pipe supports comprise a plurality of support steel pipes arranged in parallel, and the distance between two adjacent support steel pipes is equal;

the direction of the double-row steel sheet piles is the same as that of the cofferdam and the rotary spraying wall assembly, and the direction of the cofferdam and the rotary spraying wall assembly is the same as that of a coastline of the coastal beach.

3. The combination structure of steel sheet piles, cofferdams and jet grouting walls for coastal according to claim 2, characterized in that said first layer of steel sheet piles is arranged at the position of the axis of the wall-protecting high jet grouting pile of said foundation pit, and said second layer of steel sheet piles is arranged between said foundation pit and said first layer of steel sheet piles.

4. The combined structure of steel sheet piles, cofferdams and rotary spraying walls for coastal areas of claim 3, wherein the length of the first layer of steel sheet piles and the second layer of steel sheet piles is 12m, the distance between the first layer of steel sheet piles and the second layer of steel sheet piles is 2m, the distance between two adjacent support steel pipes is 4m, the distance between the steel pipe supports and the upper end face of the first layer of steel sheet piles is 1m, the upper end face of the sand layer is overlapped with the upper end face of the first layer of steel sheet piles, and the depth of the sand layer is 1.5 m.

5. The composite structure of steel sheet piles, cofferdams and jet grouting walls for coastal according to claim 1, characterized in that said cofferdams and jet grouting wall assembly comprises:

the water retaining cofferdam is arranged above the permeable layer, and the lower side surface of the water retaining cofferdam is attached to the upper side surface of the permeable layer;

the high-pressure jet grouting impervious wall is vertically arranged, the lower end of the high-pressure jet grouting impervious wall penetrates through the permeable layer and is inserted into the impermeable layer, and the upper section of the high-pressure jet grouting impervious wall is arranged in the water retaining cofferdam.

6. The combination of steel sheet piles, cofferdams and jet grouting walls for coastal according to claim 5, characterized in that said water-retaining cofferdam comprises:

a plurality of sand filling bags which are sequentially stacked into a strip structure with a trapezoidal/triangular vertical section;

the high-pressure rotary-spraying impervious wall is superposed with the axis of the water-retaining cofferdam, and the high-pressure rotary-spraying impervious wall is arranged along the length direction of the water-retaining cofferdam;

the direction of the axis of the water retaining cofferdam is the same as the direction of the coastline of the coastal beach, and the gradient of two side slopes of the water retaining cofferdam is not more than 1: 2.

7. The combined structure of steel sheet piles, cofferdams and rotary spraying walls for coastal areas of claim 6, wherein the difference between the highest point of the water-retaining cofferdam and the average high tide level is not less than 0.5m, and the highest point of the water-retaining cofferdam is arranged above the water surface;

and the distance between the lower end surface of the high-pressure rotary-spraying impervious wall and the upper side surface of the impervious layer is not less than 2 m.

8. A construction method of a combined structure of steel sheet piles, cofferdams and jet grouting walls for coastal areas, which is characterized in that the combined structure of steel sheet piles, cofferdams and jet grouting walls for coastal areas as claimed in claims 5 to 7 is constructed to the coastal beach, comprising the following steps:

determining the construction position of a foundation pit;

determining the construction positions of the cofferdam and the rotary spraying wall assembly and the double-row steel sheet piles;

constructing the cofferdam and the rotary spraying wall assembly;

constructing the double-row steel sheet piles;

and (6) excavating a foundation pit.

9. The construction method of a combined structure of steel sheet piles, cofferdams and jet grouting walls for coastal areas according to claim 8, wherein the construction of the cofferdams and jet grouting wall assemblies specifically comprises the following steps:

obtaining an average high tide level according to hydrological results, and determining the height of the water retaining cofferdam;

when the water level of the open sea side is lower than the ground elevation of the construction position of the water retaining cofferdam, laying sand filling bags;

and (5) synchronously constructing the high-pressure jet grouting impervious wall from the top of the water retaining cofferdam downwards.

10. The construction method of the combined structure of the steel sheet pile, the cofferdam and the jet grouting wall for the coastal according to claim 8, wherein the construction of the double-row steel sheet pile specifically comprises the following steps:

arranging a first layer of steel sheet piles;

a second layer of steel sheet piles is arranged inwards;

excavating a cavity with the depth of 1.5m between the first layer of steel sheet piles and the second layer of steel sheet piles;

connecting a steel pipe support at a position 1m away from the top of the first layer of steel sheet pile;

laying a geomembrane at the bottom of the cavity and on the side of the first layer of steel plate pile;

and backfilling sandy soil of the sandy soil layer.

Technical Field

The invention relates to the field of cofferdam construction, in particular to a combined structure and a construction method of a steel sheet pile, a cofferdam and a rotary spraying wall used in coastal areas.

Background

Along the beach ground, many sluice gates are built on the basis of soil with water permeability such as backfill soil, miscellaneous fill soil, silt clay and the like, and the sluice gates are often large in covering layer thickness, low in natural strength, long in consolidation drainage time and small in bearing capacity.

The method comprises the steps of creating dry-land construction conditions for a water supply gate, arranging an earth-rock cofferdam (containing a weir body and a foundation) for retaining water at the periphery of the water supply gate, and putting slopes towards a foundation pit along the position close to the foot of the cofferdam at the side of the foundation pit (the excavation slope ratio of the foundation pit is 1: 3-1: 5 generally), wherein if the slope putting of the foundation pit is slow, the required area of the foundation pit is large and exceeds the design range; if the foundation pit side slope is steep, the covering layer side slope can be unstable and slide into the foundation pit in the construction period, so that great potential safety hazard is caused to the engineering; for the water gate project with narrow site and tight construction period, the existing treatment scheme or technical measure can not meet the requirements of site construction.

Disclosure of Invention

The invention aims to solve the technical problem that the slope of the foundation pit slope can not meet the requirements of site construction in a narrow place, and aims to provide a steel sheet pile, cofferdam and rotary spraying wall combined structure and a construction method for coastal use, so as to solve the problem of water retaining in the narrow place on the coastal beach.

The invention is realized by the following technical scheme:

a composite structure of steel sheet piles, cofferdams and jet grouting walls for coastal areas, which are arranged along a beach, the coastal beach area comprises a permeable layer and a impermeable layer positioned below the permeable layer, the composite structure comprises:

the cofferdam and rotary spraying wall assembly is arranged between the open sea and the foundation pit;

the double rows of steel sheet piles are vertically arranged between the cofferdam and the rotary spraying wall assembly and the foundation pit;

double steel sheet pile includes:

the first layer of steel sheet piles are vertically arranged;

the second layer of steel sheet piles are arranged in parallel with the first layer of steel sheet piles, and gaps are formed between the first layer of steel sheet piles and the second layer of steel sheet piles;

the steel pipe support is arranged between the first layer of steel plate piles and the second layer of steel plate piles and is provided with a first end and a second end, the first end of the steel pipe support is fixedly connected with the first layer of steel plate piles, and the second end of the steel pipe support is fixedly connected with the second layer of steel plate piles;

and the sand layer is backfilled between the first layer of steel sheet piles and the second layer of steel sheet piles.

Specifically, the upper end surface of the first layer of steel sheet piles and the upper end surface of the second layer of steel sheet piles are located on the same horizontal plane, the steel pipe support comprises a plurality of support steel pipes which are arranged in parallel, and the distance between every two adjacent support steel pipes is equal;

the direction of the double-row steel sheet piles is the same as that of the cofferdam and the rotary spraying wall assembly, and the direction of the cofferdam and the rotary spraying wall assembly is the same as that of a coastline of the coastal beach.

Preferably, the first layer of steel sheet piles is arranged at the axial position of the wall-protecting high-pressure jet piles of the foundation pit, and the second layer of steel sheet piles is arranged between the foundation pit and the first layer of steel sheet piles.

As an embodiment, the lengths of the first layer of steel sheet piles and the second layer of steel sheet piles are 12m, the distance between the first layer of steel sheet piles and the second layer of steel sheet piles is 2m, the distance between two adjacent support steel pipes is 4m, the distance between the steel pipe supports and the upper end face of the first layer of steel sheet piles is 1m, the upper end face of the sandy soil layer is overlapped with the upper end face of the first layer of steel sheet piles, and the depth of the sandy soil layer is 1.5 m.

Specifically, cofferdam and rotary spray wall subassembly includes:

the water retaining cofferdam is arranged above the permeable layer, and the lower side surface of the water retaining cofferdam is attached to the upper side surface of the permeable layer;

the high-pressure jet grouting impervious wall is vertically arranged, the lower end of the high-pressure jet grouting impervious wall penetrates through the permeable layer and is inserted into the impermeable layer, and the upper section of the high-pressure jet grouting impervious wall is arranged in the water retaining cofferdam.

Preferably, the water-retaining cofferdam includes:

a plurality of sand filling bags which are sequentially stacked into a strip structure with a trapezoidal/triangular vertical section;

the high-pressure rotary-spraying impervious wall is superposed with the axis of the water-retaining cofferdam, and the high-pressure rotary-spraying impervious wall is arranged along the length direction of the water-retaining cofferdam;

the direction of the axis of the water retaining cofferdam is the same as the direction of the coastline of the coastal beach, and the gradient of two side slopes of the water retaining cofferdam is not more than 1: 2.

As another embodiment, the difference between the highest point of the water-retaining cofferdam and the average high tide level is not less than 0.5m, and the highest point of the water-retaining cofferdam is arranged above the water surface;

and the distance between the lower end surface of the high-pressure rotary-spraying impervious wall and the upper side surface of the impervious layer is not less than 2 m.

A construction method of a combined structure of a steel sheet pile, a cofferdam and a rotary spraying wall for coastal construction to a coastal beach comprises the following steps:

determining the construction position of a foundation pit;

determining the construction positions of the cofferdam and the rotary spraying wall assembly and the double-row steel sheet piles;

constructing the cofferdam and the rotary spraying wall assembly;

constructing the double-row steel sheet piles;

and (6) excavating a foundation pit.

Specifically, the construction of the cofferdam and the rotary spray wall assembly specifically comprises the following steps:

obtaining an average high tide level according to hydrological results, and determining the height of the water retaining cofferdam;

when the water level of the open sea side is lower than the ground elevation of the construction position of the water retaining cofferdam, laying sand filling bags;

and (5) synchronously constructing the high-pressure jet grouting impervious wall from the top of the water retaining cofferdam downwards.

Specifically, the construction of the double-row steel sheet pile specifically comprises the following steps:

arranging a first layer of steel sheet piles;

a second layer of steel sheet piles is arranged inwards;

excavating a cavity with the depth of 1.5m between the first layer of steel sheet piles and the second layer of steel sheet piles;

connecting a steel pipe support at a position 1m away from the top of the first layer of steel sheet pile;

laying a geomembrane at the bottom of the cavity and on the side of the first layer of steel plate pile;

and backfilling sandy soil of the sandy soil layer.

Compared with the prior art, the invention has the following advantages and beneficial effects:

according to the invention, the double-row steel sheet piles are arranged between the cofferdam and the rotary spraying wall assembly and the foundation pit to form a combined structure with the water retaining cofferdam and the high-pressure rotary spraying impervious wall, so that water is retained together and the stability of the foundation pit is ensured, the difficulties of narrow construction field, short construction period, low foundation bearing capacity and the like are overcome, and the conditions for dry construction of the water gate are created quickly.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the principles of the invention.

Fig. 1 is a schematic structural view of a combined structure of a steel sheet pile, a cofferdam and a jet grouting wall for coastal areas according to the present invention.

Reference numerals: 1-water retaining cofferdam, 2-high pressure jet grouting impervious wall, 3-impervious bed, 4-pervious bed, 5-double rows of steel sheet piles, 6-steel pipe support, 7-original ground line, 8-foundation pit and 9-open sea.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail with reference to the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are for purposes of illustration only and are not to be construed as limitations of the invention.

It should be noted that, for convenience of description, only the portions related to the present invention are shown in the drawings.

In the present invention, the embodiments and features of the embodiments may be combined with each other without conflict. The present invention will be described in detail below with reference to the accompanying drawings in conjunction with embodiments.

The sluice in this embodiment is established on permeable bed 4's basis, and permeable bed 4 in this embodiment includes backfill soil, miscellaneous fill soil, silt matter clay etc. and it possesses certain water permeability, and natural strength is low, consolidation drainage time is long, the bearing capacity is little.

Example one

A combined structure of steel sheet piles, cofferdams and rotary spraying walls for coastal areas is arranged on the coastal areas, each coastal area comprises a permeable layer 4 and a waterproof layer 3 positioned below the permeable layer 4, the combined structure comprises cofferdams and rotary spraying wall assemblies and double rows of steel sheet piles 5,

the cofferdam and rotary spraying wall assembly is arranged between the open sea 9 and the foundation pit 8, and the double-row steel sheet piles 5 are vertically arranged between the cofferdam and rotary spraying wall assembly and the foundation pit 8;

the inner sides of the cofferdam and the rotary spraying wall component are foundation pits 8 constructed in a dry land of the sluice, and the two are close to each other; in order to ensure the stability of the cofferdam foundation and the excavation of the foundation pit 8 to the designed elevation, under the condition that the field between the cofferdam and the foundation pit 8 is narrow, a stable slope (such as a slope ratio of 1: 3-1: 5) of silt or miscellaneous fill cannot be adopted, so that double rows of steel sheet piles 5 are arranged between the cofferdam and the rotary spraying wall assembly and the foundation pit 8, and the stability of the foundation pit 8 is kept by arranging the double rows of steel sheet piles 5.

The double-row steel sheet pile 5 in the embodiment comprises a first layer of steel sheet pile, a second layer of steel sheet pile, a steel pipe support 6 and a sand layer.

The first layer of steel sheet piles and the second layer of steel sheet piles used in the embodiment have the same structure, and are steel structures with linkage devices at the edges, and the linkage devices can be freely combined to form a continuous and compact retaining or water retaining wall.

The first layer of steel sheet pile/the second layer of steel sheet pile is a section steel with locking notches, and the section of the section steel has a shape of a straight plate, a groove, a Z shape and the like and has various sizes and interlocking forms. The common forms include Larson type, Lakevanna type, etc. Its advantage does: the strength is high, and the soil can be easily driven into a hard soil layer; the construction can be carried out in deep water, and an inclined support is added to form a surrounding cage if necessary. The waterproof performance is good; the cofferdams with various shapes can be formed according to the requirement.

The first layer of steel sheet piles is vertically arranged, the second layer of steel sheet piles is arranged in parallel with the first layer of steel sheet piles, and a gap is formed between the first layer of steel sheet piles and the second layer of steel sheet piles;

the steel pipe support 6 is arranged between the first layer of steel plate piles and the second layer of steel plate piles and is provided with a first end and a second end, the first end of the steel pipe support 6 is fixedly connected with the first layer of steel plate piles, and the second end of the steel pipe support 6 is fixedly connected with the second layer of steel plate piles; the steel pipe support 6 is connected with the first layer of steel sheet piles and the second layer of steel sheet piles through bracket supports.

And the sand layer is backfilled between the first layer of steel sheet piles and the second layer of steel sheet piles, so that the first layer of steel sheet piles and the second layer of steel sheet piles are fixed, and the water resistance of the sand layer can be increased.

The upper end face of the first layer of steel sheet piles and the upper end face of the second layer of steel sheet piles are positioned on the same horizontal plane, the steel pipe support 6 comprises a plurality of support steel pipes which are arranged in parallel, and the distance between every two adjacent support steel pipes is equal;

through a plurality of support steel pipes, can effectual realization to the rigidity between first floor steel sheet pile and the second floor steel sheet pile, and set up the clearance between the adjacent support steel pipe, can avoid appearing the unable condition of backfill sand layer.

In the present embodiment, since the function of the composite structure is to prevent water from the open sea 9 from entering into the foundation pit 8, the composite structure needs to be arranged along the coastline, so the direction of the double rows of steel sheet piles 5 is the same as the direction of the cofferdam and the jet grouting wall assembly, and the direction of the cofferdam and the jet grouting wall assembly is the same as the direction of the coastline of the coastal beach.

In order to protect the foundation pit 8 and avoid landslide at the edge of the foundation pit 8, the first layer of steel sheet piles are arranged at the axial line position of the wall-protecting high-spraying pile of the foundation pit 8, and the second layer of steel sheet piles are arranged between the foundation pit 8 and the first layer of steel sheet piles, so that the stability of the foundation pit 8 side slope is protected through the double rows of steel sheet piles 5.

Example two

The embodiment provides a specific structure of a cofferdam and a rotary-spraying wall assembly, which comprises a water-retaining cofferdam 1 and a high-pressure rotary-spraying impervious wall 2.

The water retaining cofferdam 1 is a temporary enclosure structure constructed for building permanent water conservancy facilities in the water conservancy project construction. The water and soil are prevented from entering the building position of the building, so that water is drained in the water retaining cofferdam 1, a foundation pit 8 is excavated, and the building is built.

The cofferdam is mainly used in hydraulic buildings in general, and the cofferdam is dismantled after being used up except for being used as a part of a formal building. The cofferdam height is higher than the highest water level that may occur during construction.

The high-pressure rotary-spraying impervious wall 2 is an underground continuous wall which is built by mixing, coagulating and hardening cement slurry sprayed in a drill hole in a soft foundation and stirred gravel soil particles by using a high-pressure spraying technology, and the high-pressure rotary-spraying impervious wall 2 can be understood and built by a person skilled in the art.

The water-retaining cofferdam 1 is arranged above the permeable layer 4, and the lower side surface of the water-retaining cofferdam 1 is attached to the upper side surface of the permeable layer 4; the water retaining cofferdam 1 is arranged above the permeable layer 4 and is mainly used for blocking seawater from entering the foundation pit 8, and the seawater can be blocked by the water retaining cofferdam 1.

The high-pressure rotary-spraying impervious wall 2 is vertically arranged, the lower end of the high-pressure rotary-spraying impervious wall 2 penetrates through the permeable layer 4 and is inserted into the impermeable layer 3, the upper section of the high-pressure rotary-spraying impervious wall 2 is arranged in the water-retaining cofferdam 1, the high-pressure rotary-spraying impervious wall 2 penetrating through the water-retaining cofferdam 1 is arranged, the purpose of fixing the water-retaining cofferdam 1 can be achieved, meanwhile, the dryness of the foundation pit 8 can be further kept in the foundation pit 8 penetrated by the permeable layer 4 of the seawater layer.

Generally, sea sand materials on coastal beaches are abundant, so the embodiment provides a method for constructing the water-retaining cofferdam 1, the water-retaining cofferdam 1 in the embodiment comprises a plurality of sand filling bags, and strip structures with trapezoidal/triangular vertical sections are sequentially stacked, the water-retaining cofferdam 1 can be set into a trapezoidal structure or a triangular structure according to specific conditions, but the general conditions are the trapezoidal structure, and the top of the water-retaining cofferdam 1 can be utilized in construction.

The high-pressure jet grouting impervious wall 2 is overlapped with the axis of the water retaining cofferdam 1, the high-pressure jet grouting impervious wall 2 is arranged along the length direction of the water retaining cofferdam 1, and the high-pressure jet grouting impervious wall 2 can further maintain the stability of the side slope of the foundation pit 8.

The direction of the axis of the water retaining cofferdam 1 is the same as the direction of the coastline of the coastal beach.

The slope of two side slopes of the water retaining cofferdam 1 is not more than 1:2, and if the slope of two side slopes of the water retaining cofferdam 1 is more than 1:2, the stability of the slope cannot be maintained, which may cause it to enter the foundation pit 8.

EXAMPLE III

The embodiment provides a construction method for constructing the above-mentioned combined structure of steel sheet pile, cofferdam and jet grouting wall for coastal to coastal beach, which includes the following steps:

and S1, determining the construction position of the foundation pit 8, and determining the foundation pit 8 through the installation position of the water conservancy facility, the slope ratio, the geological condition, the construction environment and the like before construction.

And S2, determining the construction positions of the cofferdam and the rotary spraying wall assembly and the double-row steel sheet piles 5, and determining the positions of the cofferdam and the rotary spraying wall assembly and the double-row steel sheet piles 5 by combining a shoreline and the like according to the determined construction position of the foundation pit 8.

And S3, constructing the cofferdam and the rotary spraying wall assembly, and constructing the cofferdam and the rotary spraying wall assembly firstly after the positions are determined.

S31, obtaining an average high tide level according to hydrological results (which can be obtained from data such as rising tide and ebbing tide) and determining the height of the water-retaining cofferdam 1, wherein the height of the water-retaining cofferdam 1 needs to be higher than the average high tide level, so that the situation that seawater overflows the water-retaining cofferdam 1 and enters the foundation pit 8 can be avoided.

S32, when the water level of the open sea 9 side is lower than the ground elevation of the construction position of the water-retaining cofferdam 1, laying sand filling bags, and carrying out layered hydraulic fill construction from bottom to top, namely, the laying sand filling bags and the construction of the high-pressure rotary-spraying impervious wall 2 need to be carried out synchronously, and the construction of the whole cofferdam and the rotary-spraying wall assembly is completed gradually.

S33, synchronously constructing a high-pressure rotary-spraying impervious wall 2 downwards from the top of the water-retaining cofferdam 1, arranging the high-pressure rotary-spraying impervious wall 2 at the axis of the water-retaining cofferdam 1, enabling the upper part of the wall to be as high as the top of the cofferdam, and enabling the bottom of the wall to penetrate through a permeable layer 4 such as backfill, a sludge layer and the like and enter a impermeable layer 3.

S4, constructing double rows of steel sheet piles 5;

s41, arranging a first layer of steel sheet piles;

s42, arranging a second layer of steel sheet piles inwards; the position of the double-row steel sheet piles 5 is determined through the first layer of steel sheet piles, and then the second layer of steel sheet piles is arranged on the inner side of the double-row steel sheet piles.

S43, excavating a 1.5m deep cavity between the first layer of steel sheet piles and the second layer of steel sheet piles, and excavating soil of a permeable layer 4 between the first layer of steel sheet piles and the second layer of steel sheet piles.

And S44, connecting the steel pipe supports 6 at a position 1m away from the top of the first layer of steel plate pile, and then connecting the steel pipe supports 6 through welding or other methods to fix the first layer of steel plate and the second layer of steel plate.

S45, laying a geomembrane at the bottom of the cavity and on the pile side of the first layer of steel plates;

and S46, backfilling sandy soil of the sandy soil layer, wherein the sandy soil can be the same as the sand filling bag.

S5, excavating the foundation pit 8 after slope excavation or reinforcing by adopting double rows of steel sheet piles 5 and the like, and monitoring displacement and uplift quantity of deep soil bodies on two sides of the foundation pit 8 to ensure that the combined structure is not subjected to sliding damage.

The structure and the method in the embodiment can also be used for similar projects, such as buildings, such as pump stations, water intakes, highway piers and the like built on beach lands.

Example four

The present embodiment provides a specific embodiment, and the present embodiment is: in the sea wall engineering of an industrial park in Ningde City of Fujian province, a water gate is arranged at the right side of the sea wall, the excavation of a foundation pit 8 at the outer side is revealed as a weak layer such as backfill soil, miscellaneous fill soil, silt and the like, the excavation and slope placing in the foundation pit 8 can not form a stable side slope-slope ratio (such as 1:3), and the condition of arranging a high-spraying pile retaining wall is not met.

The construction steps of the embodiment comprise:

the first step, the construction position of the foundation pit 8, the construction positions of the cofferdam and the rotary spraying wall assembly and the double-row steel sheet piles 5 are determined according to the environmental conditions.

The grade of the water gate protected by the water retaining cofferdam 1 is 4, the water retaining time of the water retaining cofferdam 1 is 1 year, the flood standard adopts 10-year recurrence period tide level, and the corresponding tide level is 4.93 m. The ratio of the inner slope to the outer slope is 1:2, the width of the weir crest is 4.0m, and the elevation of the weir crest is 6.00 m.

And secondly, constructing a cofferdam and a rotary spraying wall assembly.

When the water level at the open sea 9 side is lower than the original ground elevation of the water retaining cofferdam 1, the sand filling bag is unfolded along the laying position by using a barge, the ground is laid on water, the ground is leveled before filling, and projections and sundries which damage the ground are cleaned.

Carry out the layering hydraulic reclamation construction from bottom to top, it faces the sea side, faces 8 side slopes of foundation ditch and is not all steeper than 1:2, the cofferdam top elevation is about 0.5m higher than the average high sea level.

The local sea sand material is rich, and the weir body is a hydraulic filling sand bag cofferdam; the stratum at the lower part of the water retaining cofferdam 1 is mainly silt deposited by a coastal phase, is in a flow plastic shape, has large single-layer thickness (18-28.5 m), high water content, low strength and high compressibility, has large deformation after loading, is easy to generate sliding damage, and needs longer time for stable consolidation.

In order to ensure the seepage-proofing effect and the stability of the side slope of the foundation pit 8, the weir base is provided with a high-pressure jet-grouting seepage-proofing wall 2 which passes through the silt layer, the maximum depth of the entering silt is about 30m, the lower end of the high-pressure jet-grouting seepage-proofing wall 2 enters the impervious layer for 32m, and the distance between single-row high jet holes is 0.8 m.

By combining hydrology and geological conditions of an engineering area and the technical requirements of high-pressure rotary spraying wall construction, a triple-pipe high-pressure rotary spraying process is adopted, and a rotary spraying wall condensate with larger diameter and higher strength is formed in a foundation, so that the seepage-proofing and reinforcing effects of the high-pressure rotary spraying wall are enhanced.

And thirdly, constructing double rows of steel sheet piles 5.

A first layer of steel sheet piles are arranged at the axial line position of the original retaining wall high-pressure jet pile, a second layer of steel sheet piles are arranged 2m inwards, the type of the double-row steel sheet piles 5 is SP-IV type, the depth is 12m, and the pile tops of the double-row steel sheet piles 5 are flush with the original ground line 7.

Excavating a first layer of steel sheet piles and a second layer of steel sheet piles to a depth of 1.5m, arranging DN300 multiplied by 6 supporting steel pipes at a position of 1m, arranging a horizontal interval between every two adjacent supporting steel pipes to be 4.0m, adopting I32 b I-shaped steel for the enclosing purlin, and arranging bracket supports;

and paving anti-seepage geomembranes at the bottom and the first layer of steel sheet piles, and backfilling sandy soil between the first layer of steel sheet piles and the second layer of steel sheet piles after the construction of the steel pipe support 6 is finished.

And fourthly, excavating a foundation pit 8.

After the construction of the double-row steel sheet piles 5, the cofferdam and the rotary spraying wall assembly is completed, the excavation of the foundation pit 8 can be carried out.

The construction is carried out on site according to the design, the combined structure of the double-row steel sheet piles 5, the cofferdam and the high-pressure rotary spraying wall is quickly formed and plays a role, the measured seepage amount in the foundation pit 8 is small, the dry land construction condition of a construction site is guaranteed, a solid foundation is laid for the construction of the seepage-proofing engineering and the main engineering of the water gate foundation, and the water gate is basically finished before flood season and meets the requirement of image and appearance of flood season.

In summary, in the embodiment, the relative position relationship between each component is as follows: the length of first layer steel sheet pile and second floor steel sheet pile is 12m, and the distance between first layer steel sheet pile and the second floor steel sheet pile is 2m, and the distance between two adjacent support steel pipes is 4m, and the distance between the up end of steel pipe support 6 and first layer steel sheet pile is 1m, and the up end of sand bed and the up end coincidence of first layer steel sheet pile, the degree of depth of sand bed is 1.5 m.

The difference between the highest point of the water-retaining cofferdam 1 and the average high tide level is not less than 0.5m, and the highest point of the water-retaining cofferdam 1 is arranged above the water surface;

the distance between the lower end surface of the high-pressure jet grouting impervious wall 2 and the upper side surface of the impervious layer 3 is not less than 2 m.

In the description herein, reference to the description of the terms "one embodiment/mode," "some embodiments/modes," "example," "specific example," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment/mode or example is included in at least one embodiment/mode or example of the application. In this specification, the schematic representations of the terms used above are not necessarily intended to be the same embodiment/mode or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments/modes or examples. Furthermore, the various embodiments/aspects or examples and features of the various embodiments/aspects or examples described in this specification can be combined and combined by one skilled in the art without conflicting therewith.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present application, "plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

It will be understood by those skilled in the art that the foregoing embodiments are merely for clarity of description and are not intended to limit the scope of the invention. It will be apparent to those skilled in the art that other variations or modifications may be made on the above invention and still be within the scope of the invention.