CN108385651B - Design and construction method for reinforcing soft foundation by using composite geotextile - Google Patents

Design and construction method for reinforcing soft foundation by using composite geotextile Download PDF

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CN108385651B
CN108385651B CN201810243664.9A CN201810243664A CN108385651B CN 108385651 B CN108385651 B CN 108385651B CN 201810243664 A CN201810243664 A CN 201810243664A CN 108385651 B CN108385651 B CN 108385651B
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geotextile
sand cushion
layer
cushion layer
geogrid
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CN108385651A (en
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仉文岗
杨昌友
张艳梅
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Chongqing University
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    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D3/00—Improving or preserving soil or rock, e.g. preserving permafrost soil
    • E02D3/005—Soil-conditioning by mixing with fibrous materials, filaments, open mesh or the like
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D1/00—Investigation of foundation soil in situ
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D3/00—Improving or preserving soil or rock, e.g. preserving permafrost soil
    • E02D3/02—Improving by compacting
    • E02D3/10—Improving by compacting by watering, draining, de-aerating or blasting, e.g. by installing sand or wick drains
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D2300/00—Materials
    • E02D2300/0085—Geotextiles
    • E02D2300/009—Geotextiles with multi-layer structure

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  • Life Sciences & Earth Sciences (AREA)
  • Structural Engineering (AREA)
  • Mining & Mineral Resources (AREA)
  • Soil Sciences (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Paleontology (AREA)
  • Civil Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Agronomy & Crop Science (AREA)
  • Environmental & Geological Engineering (AREA)
  • Analytical Chemistry (AREA)
  • Chemical & Material Sciences (AREA)
  • Investigation Of Foundation Soil And Reinforcement Of Foundation Soil By Compacting Or Drainage (AREA)

Abstract

The invention discloses a design and construction method for reinforcing a soft foundation by using a composite geotextile, which is characterized by comprising the following steps of: laying geotextile on the ground surface, and laying a first sand cushion layer with the thickness of 30cm above the geotextile; adopting a PCC pile machine to drive the composite geotextile as the vertical drainage body into the lower part of the soft soil foundation, and then laying a first layer of geogrid and a second layer of sand cushion layer; laying a second layer of geogrid on the second layer of sand cushion layer, and arranging drainage ditches at two sides of the embankment, wherein the drainage ditches are positioned at the foot line of the embankment; burying a settlement plate and a displacement side pile; compacting the ground surface on which the sand cushion is paved; the roadbed is compacted to a stacking design elevation in a layered filling mode, the stacking prepressing time is 10-12 months, the composite geotextile which is squeezed into the soft foundation is used as a vertical drainage body to discharge water in soil, the soil consolidation is accelerated, and the geogrid laid on each sand cushion layer effectively guarantees uniform descending of the cushion layer.

Description

Design and construction method for reinforcing soft foundation by using composite geotextile
Technical Field
The invention relates to the technical field of geotechnical engineering soft foundation treatment, in particular to a design and construction method for reinforcing a soft foundation by using a composite geotextile.
Background
The rainfall capacity in south China and most regions on coastal areas is large, the groundwater level is high, soil bodies are soft soil with high water content, and in addition, the rapid development of city construction process, the coastal areas in China are increasingly in shortage, in order to obtain more land resources, land reclamation projects for surrounding sea are more and more, the soil bodies are mostly saturated soft clay, the water content is high, the pore ratio is large, the bearing capacity is low, the soil bodies have high compressibility, the project construction can not be directly carried out on the soil bodies, the soil bodies need to be subjected to drainage treatment before construction of roads, airports and the like is carried out, the groundwater level is reduced, the pore ratio of the soil bodies is reduced, the bearing capacity of the soil bodies is enhanced, and the post-construction settlement.
At present, common soft foundation drainage consolidation methods comprise surcharge preloading, vacuum combined surcharge preloading and the like, a vacuum pipeline needs to be laid by adopting the vacuum preloading, a vacuumizing device is arranged, the operation is complex compared with the surcharge preloading, the construction cost can be increased, and in addition, the internal consolidation degree of a foundation is difficult to detect in the vacuumizing process. In the prior art, vertical drainage plates are mostly adopted as drainage bodies, but the method has limited improvement on the strength of the soil body for drainage and reinforcement and has lower ductility of the soil body.
Therefore, the research on the drainage consolidation method which can greatly improve the strength and the ductility of the soil body is still blank.
Disclosure of Invention
The invention aims to solve the problems in the prior art and provides a design and construction method for reinforcing a soft foundation by using a composite geotextile.
The technical scheme adopted for achieving the aim of the invention is that the design for reinforcing the soft foundation by using the composite geotextile is characterized in that: the composite geotextile, the first sand cushion layer, the first geogrid, the second sand cushion layer, the second geogrid, the sedimentation plate, the displacement side pile and the drainage ditch are included.
Geotextile, a first sand cushion layer, a first geogrid, a second sand cushion layer and a second geogrid are sequentially laid on the earth surface of the construction area from bottom to top.
The thickness of the geotextile is 2.4-3.0 mm, and the mass per unit area is 300-400 g/mm2. The thickness of the first sand cushion layer is 30-35 cm. The first sand cushion layer is 4-30 mm in gradation. The unit area weight of the first layer of geogrid is 200-240 g/m2. The thickness of the second sand cushion layer is 20-25 cm, and the gradation is 4-30 mm. The unit area weight of the second layer of geogrid is 200-240 g/m2。
A plurality of vertical drainage bodies are arranged below the soft soil foundation in the construction area. The vertical drainage body is of a hollow cylinder structure with two open ends.
The vertical drainage body is a composite geotextile. The composite geotextile comprises two layers of non-woven geotextile and one layer of woven geotextile. The woven geotextile is positioned between two layers of nonwoven geotextile.
From the processing point of view, the vertical drainage body is a hollow cylinder structure formed by rolling the composite geotextile, and the diameter of the cylinder structure is 1.5 m. The joint of the cylindrical structure is sewn, and the length of the sewn lap joint is 10-15 cm.
And a settlement plate and a displacement side pile are embedded at the observation point. And drainage ditches are arranged on two sides of the embankment and are positioned at the foot line of the embankment.
A construction method for reinforcing a soft foundation by using a composite geotextile is characterized by comprising the following steps:
1) and cleaning the earth surface of the construction area and leveling the ground.
2) And laying geotextile on the cleaned and leveled ground surface, and laying a first sand cushion layer above the geotextile.
The thickness range of the geotextile is 2.4-3.0 mm, and the mass per unit area is 300-400 g/mm2。
The thickness of the first sand cushion layer is 30-35 cm. The first sand cushion layer is 4-30 mm in gradation.
3) And (4) using a PCC pile machine to drive the vertical drainage body into the lower part of the soft soil foundation.
And laying a first layer of geogrid above the first layer of sand cushion layer, and laying a second layer of sand cushion layer above the first layer of geogrid.
The vertical drainage body is of a hollow cylinder structure with two open ends. The vertical drainage body is made of a composite geotextile, and the composite geotextile comprises two layers of non-woven geotextiles and one layer of woven geotextile. The woven geotextile is positioned between two layers of nonwoven geotextile.
From the processing point of view, the vertical drainage body is a hollow cylinder structure rolled by the composite geotextile, and the joint of the cylinder structure is sewed. The diameter of the vertical drainage body is 1.5m, and the lap joint length after sewing is 10-15 cm.
The unit area weight of the first layer of geogrid is 200-240 g/m2。
The thickness of the second sand cushion layer is 20-25 cm, and the gradation is 4-30 mm.
4) And laying a second layer of geogrid above the second layer of sand cushion layer, and arranging drainage ditches at two sides of the embankment, wherein the drainage ditches are positioned at the foot line of the embankment.
The unit area weight of the second layer of geogrid is 200-240 g/m2。
5) And burying a settlement plate and a displacement side pile.
6) And compacting the ground surface after the sand cushion layer is paved.
7) And (4) carrying out layered filling and compaction on the roadbed to a stacking design elevation, wherein the stacking and pre-compaction time is 10-12 months.
And furthermore, cofferdams are arranged on two sides of the construction area, and water is pumped and dried.
Further, 50-60 cm of excess length is left on the surface of the first sand cushion layer of each roll of the composite geotextile.
Further, the PCC stake machine includes a vibrating head, a pile mold and a valve shoe.
Furthermore, the punched composite geotextile is arranged in a square shape, and the side length of the square arrangement is 3 m.
Furthermore, three settlement observation points are arranged and are respectively positioned at the central axis of the road and 0.5m inside the slope shoulder sidelines at two sides, and two settlement plates are buried in each observation point.
Furthermore, the displacement side piles are arranged at two sides of the displacement side piles along the outer side of the slope toe side line every 10m, the number of the displacement side piles is 4, the displacement side piles and the position of the settlement plate are on the same straight line, the embedding depth of the displacement side piles is not less than 1.2m, and the height of the pile top exposed out of the ground is not more than 10 cm.
Furthermore, the sedimentation plate is made of steel, the size of the bottom plate is 40cm by 40cm, and the thickness of the bottom plate is 0.8 cm. The displacement side pile is prefabricated by reinforced concrete, the mark of the concrete is not less than C25, the section is rectangular, and the size of the cross section is 15cm by 15 cm.
Further, in the step 6), a vibratory roller of 20t is selected for rolling in the compaction treatment, the two rollers use the central line as a boundary and each roller presses the width of the semi-radial roadbed, the rolling is performed in a longitudinal advancing and retreating mode from two sides to the center, the rolling is performed with the track overlapping by 0.4m, and the adjacent two sections are longitudinally overlapped by 2.0 m.
The technical effects of the present invention are undoubted, and the present invention has the following advantages:
1) the selected woven geotextile and the non-woven geotextile have high tensile strength and small deformation under the action of tension, the outer two layers of non-woven geotextile can better filter fine particles and prevent soil from losing, and the woven geotextile sandwiched in the middle is woven neatly and has better water permeability;
2) the composite geotextile roll made of the woven geotextile and the non-woven geotextile selected by the invention has certain reinforcement effect while being thrown into the soil body for drainage, and the composite geotextile can well restrain the lateral deformation of the inner soil body when the upper load is acted, thereby improving the soil body strength and increasing the soil body ductility to a certain extent;
3) the invention has the advantages of wide material source, low price and no pollution, can effectively reduce the construction cost of drainage consolidation, and simultaneously, the vertical drainage bodies arranged in a driving way are less dense compared with the traditional vertical drainage plates, so the construction period can be effectively shortened and the cleanness of the construction site can be kept.
Drawings
FIG. 1 is a schematic structural diagram of an embankment of the present invention after being stacked;
fig. 2 is a schematic plan view of the composite geotextile of the present invention;
fig. 3 is a schematic view of the placement of the composite geotextile of the present invention within a sand cushion layer;
fig. 4 is a schematic composition of the composite geotextile of the present invention;
figure 5 is a schematic view of a settlement plate and displacement side piling arrangement of the present invention;
fig. 6 is a schematic view of the construction process of the composite geotextile.
In the figure: composite geotextile 1, non-woven geotextile 101, woven geotextile 102, geotextile 2, first sand cushion layer 3, first geogrid 4, second sand cushion layer 5, second geogrid 6, settling plate 7, displacement side pile 8, PCC pile machine 9, vibrating head 901, pile mold 902, valve pile shoe 903, drainage ditch 10 and cofferdam 11.
Detailed Description
The present invention is further illustrated by the following examples, but it should not be construed that the scope of the above-described subject matter is limited to the following examples. Various substitutions and alterations can be made without departing from the technical idea of the invention and the scope of the invention is covered by the present invention according to the common technical knowledge and the conventional means in the field.
Example 1:
as shown in fig. 1, a design for reinforcing soft foundation by using composite geotextile is characterized in that: the composite geotextile comprises a composite geotextile 1, geotextile 2, a first sand cushion layer 3, a first geogrid 4, a second sand cushion layer 5, a second geogrid 6, a settling plate 7, a displacement side pile 8 and a drainage ditch 10.
Geotextile 2, a first sand cushion layer 3, a first geogrid 4, a second sand cushion layer 5 and a second geogrid 6 are sequentially laid on the earth surface of the construction area from bottom to top.
The thickness of the geotextile 2 is 2.4-3.0 mm, and the mass per unit area is 300-400 g/mm2。
The thickness of the first sand cushion layer 3 is 30-35 cm. The 3-grade composition of the first sand cushion layer is 4-30 mm.
The unit area weight of the first layer of geogrid 4 is 200-240 g/m2。
The thickness of the second sand cushion layer 5 is 20-25 cm, and the gradation is 4-30 mm.
The second layer of geogrid 6 has the weight of 200-240 g/m in unit area2。
A plurality of vertical drainage bodies are arranged below the soft soil foundation in the construction area. The vertical drainage body is of a hollow cylinder structure with two open ends. The punched composite geotextile 1 is arranged in a square shape, and the side length of the square arrangement is 3 m.
The vertical drainage body is a composite geotextile 1. The composite geotextile 1 comprises two layers of non-woven geotextile 101 and one layer of woven geotextile 102. The woven geotextile 102 is located between two layers of nonwoven geotextile 101.
From the viewpoint of processing, the vertical drainage body is a hollow cylindrical structure formed by rolling the composite geotextile 1, and the diameter of the cylindrical structure is 1.5 m. The joint of the cylindrical structure is sewn, and the length of the sewn lap joint is 10-15 cm.
And 50-60 cm of excess length is left on the surface of the first sand cushion layer 3 of each roll of the composite geotextile 1.
And a settlement plate 7 and a displacement side pile 8 are embedded at the observation point. Drainage ditches 10 are arranged on two sides of the embankment, and the drainage ditches 10 are located on the foot line of the embankment. Cofferdams 11 are arranged on two sides of the construction area, and water pumping and air drying are carried out.
The three settlement observation points are respectively positioned at the central axis of the road and 0.5m inside the slope shoulder sidelines at two sides, and two settlement plates 7 are buried in each observation point.
The displacement side piles 8 are arranged at two sides of each side pile every 10m along the outside of the slope toe side line, 4 displacement side piles are arranged at two sides of each side pile and are positioned on the same straight line with the position of the settlement plate 7, the embedding depth of each displacement side pile 8 is not less than 1.2m, and the height of the pile top exposed out of the ground is not more than 10 cm.
The settling plate 7 is made of steel, the size of the bottom plate is 40cm by 40cm, and the thickness of the bottom plate is 0.8 cm. The displacement side pile 8 is prefabricated by reinforced concrete, the mark of the concrete is not less than C25, the section is rectangular, and the size of the cross section is 15cm by 15 cm.
Example 2:
a construction method for reinforcing a soft foundation by using a composite geotextile is characterized by comprising the following steps:
1) and cleaning the earth surface of the construction area and leveling the ground.
Cofferdams 11 are arranged on two sides of the construction area, and water pumping and air drying are carried out.
2) And laying the geotextile 2 on the cleaned and leveled ground surface, and laying the first sand cushion layer 3 above the geotextile 2.
The thickness range of the geotextile 2 is 2.4-3.0 mm, and the mass per unit area is 300-400 g/mm2。
The thickness of the first sand cushion layer 3 is 30-35 cm. The 3-grade composition of the first sand cushion layer is 4-30 mm.
3.1) using a PCC pile machine 9 to drive the vertical drainage body into the lower part of the soft soil foundation. The PCC pile driver 9 comprises a vibrating head 901, a pile mould 902 and a valve shoe 903.
As shown in FIG. 6, i.e.A schematic drawing of the procedure for the composite geotextile 1 is provided, according to A1To A7The process is operated.
A1The process comprises the following steps: the PCC pile machine 9 is in place, and the valve pile shoe 903 is kept closed;
A2the process comprises the following steps: the pile is sunk using the vibrational energy of the vibrational head 901 at the top of the PCC pile machine 9.
A3、A4The process comprises the following steps: and stopping pile sinking after the pile mould reaches a set depth, taking down the top vibrating head 901, and putting the prepared composite geotextile 1 into the pile mould 902 of the PCC pile machine 9.
A5The process comprises the following steps: after the composite geotextile 1 is placed, a vibration head 901 is installed;
A6the process comprises the following steps: opening the valve pile shoe 903, lifting the PCC pile machine 9 upwards, and then leaving the internal composite geotextile 1 in the soil body as a vertical drainage body;
A7the process comprises the following steps: and (4) completely lifting the PCC pile machine 9 to complete the driving of the composite geotextile 1.
3.2) laying a first layer of geogrid 4 above the first layer of sand cushion layer 3, and laying a second layer of sand cushion layer 5 above the first layer of geogrid 4.
The vertical drainage body is of a hollow cylinder structure with two open ends. As shown in fig. 4, the vertical drainage body is made of a composite geotextile 1, and the composite geotextile 1 comprises two layers of non-woven geotextiles 101 and one layer of woven geotextile 102. The woven geotextile 102 is located between two layers of nonwoven geotextile 101.
From the processing point of view, the vertical drainage body is a hollow cylinder structure formed by rolling the composite geotextile 1, and the joint of the cylinder structure is sewed. The diameter of the vertical drainage body is 1.5m, and the lap joint length after sewing is 10-15 cm.
As shown in fig. 3, 50-60 cm of extra length is left on the surface of the first sand cushion layer 3 of each roll of the composite geotextile 1.
As shown in fig. 2, the punched composite geotextile 1 is arranged in a square shape, and the side length of the square arrangement is 3 m.
The unit area weight of the first layer of geogrid 4 is 200-240 g/m2。
The thickness of the second sand cushion layer 5 is 20-25 cm, and the gradation is 4-30 mm.
4) And laying a second layer of geogrid 6 above the second layer of sand cushion layer 5, and arranging drainage ditches 10 on two sides of the embankment, wherein the drainage ditches 10 are positioned at the foot line of the embankment.
The second layer of geogrid 6 has the weight of 200-240 g/m in unit area2。
5) As shown in fig. 1 and 5, the settling plate 7 and the displacement side piles 8 are buried.
Three settlement observation points are arranged and respectively located at the central axis of the road and 0.5m inside the side lines of the slope shoulders on two sides, and two settlement plates 7 are buried in each observation point.
In the concrete implementation, a soil pit of about 40cm multiplied by 40cm is dug at an embedding place, sand with the thickness of 5-10 cm is filled in the pit for leveling and compaction, the sedimentation plate 7 is horizontally placed in the pit, the periphery of the pit is filled with sand and leveled, then soil is backfilled for leveling and compaction, when filling is carried out, the periphery of the sedimentation plate 7 is filled with the filler for compaction so as to protect the sedimentation plate 7, the protective sleeve is embedded at a position 30cm above the bottom plate, in order to prevent the sedimentation plate 7 and the measuring rod from being damaged during construction, the periphery of the protective sleeve is tamped by a small-sized tamping machine, the outer side of the sleeve is coated with a layer of striking color, and a small red flag is inserted on.
Along with the increase of the filled soil, the measuring rod and the sleeve are correspondingly connected to be higher, and the vertical deviation rate is not more than 1.5% when the measuring rod and the sleeve are connected to be higher. After the height of the measuring rod and the sleeve sealing cover is connected, the height of the measuring rod and the sleeve sealing cover does not exceed 50cm of the soil surface. The stability and the perpendicularity of the measuring rod are ensured when the roadbed is filled, and the inclination of the settlement plate 7 and the measuring rod is not more than 1 degree when the connecting height of the settlement plate and the measuring rod reaches 4 meters.
The displacement side piles 8 are arranged at two sides of each side pile every 10m along the outside of the slope toe side line, 4 displacement side piles are arranged at two sides of each side pile and are positioned on the same straight line with the position of the settlement plate 7, the embedding depth of each displacement side pile 8 is not less than 1.2m, and the height of the pile top exposed out of the ground is not more than 10 cm. The embedding method adopts driving or digging embedding, the periphery of the pile is required to be backfilled compactly, 50cm of the upper part of the periphery of the pile is poured and fixed by concrete, and the displacement side pile 8 is ensured to be embedded stably.
The settling plate 7 is made of steel, the size of the bottom plate is 40cm by 40cm, and the thickness of the bottom plate is 0.8 cm. The displacement side pile 8 is prefabricated by reinforced concrete, the mark of the concrete is not less than C25, the section is rectangular, and the size of the cross section is 15cm by 15 cm.
6) And compacting the ground surface after the sand cushion layer is paved.
And 6) rolling by using a 20t vibratory roller in the step 6), wherein two rollers are used for rolling by taking a central line as a boundary and each half-spoke roadbed width, and rolling is performed in a longitudinal advancing and retreating mode from two sides to the center, wherein the rolling is performed by overlapping the track of the roller by 0.4m and longitudinally overlapping two adjacent sections by 2.0m, so that no pressure leakage and dead angle are ensured, and the rolling uniformity is ensured.
The rolling method in the compaction process comprises the following steps: and carrying out static pressing once, carrying out weak vibration rolling once, carrying out strong vibration rolling 3-6 times, carrying out weak vibration rolling once, and carrying out static pressing once again to eliminate wheel tracks.
7) And (4) carrying out layered filling and compaction on the roadbed to a stacking design elevation, wherein the stacking and pre-compaction time is 10-12 months.
The rolling method in the compaction process comprises the following steps: and carrying out static pressing once, carrying out weak vibration rolling once, carrying out strong vibration rolling 3-6 times, carrying out weak vibration rolling once, and carrying out static pressing once again to eliminate wheel tracks.
The method has the advantages of simple and easy operation and easy realization, the selected woven geotextile and the non-woven geotextile have high tensile strength and small deformation under the action of tension, the outer two layers of non-woven geotextile can better filter fine particles and prevent soil from losing, and the woven geotextile sandwiched in the middle is orderly woven and has better water permeability. The composite geotextile roll made of the woven geotextile and the non-woven geotextile is used for draining water when being thrown into a soil body, and has a certain reinforcement effect, and the composite geotextile can well restrain the lateral deformation of the inner soil body when an upper load is acted, so that the soil body strength is improved to a certain extent, and the soil body ductility is increased.

Claims (9)

1. A design method for reinforcing a soft foundation by using a composite geotextile is characterized by comprising the following steps: the composite geotextile comprises a composite geotextile (1), geotextile (2), a first sand cushion layer (3), a first geogrid (4), a second sand cushion layer (5), a second geogrid (6), a settling plate (7), a displacement side pile (8) and a drainage ditch (10);
the earth surface of the construction area is sequentially paved with a geotextile (2), a first sand cushion layer (3), a first geogrid (4), a second sand cushion layer (5) and a second geogrid (6) from bottom to top;
the thickness of the geotextile (2) is 2.4-3.0 mm, and the mass per unit area is 300-400 g/mm 2; the thickness of the first sand cushion layer (3) is 30-35 cm; the gradation of the first sand cushion layer (3) is 4-30 mm; the unit area weight of the first layer of geogrid (4) is 200-240 g/m 2; the thickness of the second sand cushion layer (5) is 20-25 cm, and the gradation is 4-30 mm; the unit area weight of the second layer of geogrid (6) is 200-240 g/m 2;
a plurality of vertical drainage bodies are arranged below a soft soil foundation in a construction area; the vertical drainage body is of a cylindrical structure with two open ends and a hollow interior;
the vertical drainage body is a composite geotextile (1); the composite geotextile (1) comprises two layers of non-woven geotextiles (101) and one layer of woven geotextile (102); the woven geotextile (102) is positioned between two layers of non-woven geotextile (101);
from the processing point of view, the vertical drainage body is a hollow cylinder structure rolled by the composite geotextile (1), and the diameter of the cylinder structure is 1.5 m; the joints of the cylindrical structures are sewn, and the length of the sewn lap joints is 10-15 cm; each roll of the composite geotextile (1) is reserved with a surplus length of 50-60 cm on the surface of the first sand cushion layer (3);
a settlement plate (7) and a displacement side pile (8) are embedded at the observation point; and drainage ditches (10) are arranged on two sides of the embankment, and the drainage ditches (10) are positioned at the foot line of the embankment.
2. A construction method for reinforcing a soft foundation by using a composite geotextile is characterized by comprising the following steps:
1) cleaning the earth surface of the construction area and leveling the ground;
2) laying geotextile (2) on the cleaned and leveled ground surface, and laying a first sand cushion layer (3) above the geotextile (2);
the thickness range of the geotextile (2) is 2.4-3.0 mm, and the mass per unit area is 300-400 g/mm 2;
the thickness of the first sand cushion layer (3) is 30-35 cm; the gradation of the first sand cushion layer (3) is 4-30 mm;
3) using a PCC pile machine (9) to drive the vertical drainage body into the lower part of the soft soil foundation;
a first geogrid (4) is laid above the first sand cushion layer (3), and a second sand cushion layer (5) is laid above the first geogrid (4);
the vertical drainage body is of a cylindrical structure with two open ends and a hollow interior; the vertical drainage body is made of a composite geotextile (1), and the composite geotextile (1) comprises two layers of non-woven geotextiles (101) and one layer of woven geotextile (102); the woven geotextile (102) is positioned between two layers of non-woven geotextile (101);
from the aspect of processing, the vertical drainage body is a hollow cylindrical structure rolled by the composite geotextile (1), and joints of the cylindrical structure are sewn; the diameter of the vertical drainage body is 1.5m, and the lap joint length after sewing is 10-15 cm;
the unit area weight of the first layer of geogrid (4) is 200-240 g/m2；
The thickness of the second sand cushion layer (5) is 20-25 cm, and the gradation is 4-30 mm;
4) a second layer of geogrid (6) is laid above the second layer of sand cushion layer (5), drainage ditches (10) are arranged on two sides of the embankment, and the drainage ditches (10) are located at the toe line of the embankment;
the unit area weight of the second layer of geogrid (6) is 200-240 g/m 2;
5) burying a settlement plate (7) and a displacement side pile (8);
6) compacting the ground surface on which the sand cushion is paved;
7) and (4) carrying out layered filling and compaction on the roadbed to a stacking design elevation, wherein the stacking and pre-compaction time is 10-12 months.
3. The construction method for soft foundation reinforcement by using the composite geotextile as claimed in claim 2, wherein: cofferdams (11) are arranged on two sides of the construction area, and water pumping and air drying are carried out.
4. The construction method for soft foundation reinforcement by using the composite geotextile as claimed in claim 2, wherein: the PCC pile machine (9) comprises a vibrating head (901), a pile die (902) and a valve pile shoe (903).
5. The construction method for soft foundation reinforcement by using the composite geotextile as claimed in claim 2, wherein: the punched composite geotextile (1) is arranged in a square shape, and the side length of the square arrangement is 3 m.
6. The construction method for soft foundation reinforcement by using the composite geotextile as claimed in claim 2, wherein: three settlement observation points are arranged and respectively positioned at the central axis of the road and 0.5m inside the sidelines of the slope shoulders at two sides, and two settlement plates (7) are buried in each observation point.
7. The construction method for soft foundation reinforcement by using the composite geotextile as claimed in claim 2, wherein: the displacement side piles (8) are arranged at two sides of each side along the outer edge of the slope toe by 10m, the number of the displacement side piles is 4, the displacement side piles and the position of the settlement plate (7) are on the same straight line, the embedding depth of the displacement side piles (8) is not less than 1.2m, and the height of the pile top exposed out of the ground is not more than 10 cm.
8. The construction method for soft foundation reinforcement by using the composite geotextile as claimed in claim 2, wherein: the sedimentation plate (7) is made of steel, the size of the bottom plate is 40cm by 40cm, and the thickness of the bottom plate is 0.8 cm; the displacement side pile (8) is prefabricated by reinforced concrete, the mark of the concrete is not less than C25, the section of the displacement side pile is rectangular, and the size of the cross section is 15cm by 15 cm.
9. The construction method for soft foundation reinforcement by using the composite geotextile as claimed in claim 2, wherein: and 6) in the step 6), a vibratory roller of 20t is selected for rolling, the two rollers use the central line as a boundary and each roller presses the width of the semi-radial roadbed, the rolling is performed in a longitudinal advancing and retreating mode from two sides to the center, the rolling is performed with the track overlapping by 0.4m, and the adjacent two sections are longitudinally overlapped by 2.0 m.
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