CN112900177A

CN112900177A - Composite geomembrane salt-separating water-blocking partition layer structure

Info

Publication number: CN112900177A
Application number: CN202110141530.8A
Authority: CN
Inventors: 周玉利; 晁刚; 王亚玲; 马亮; 郝广杰
Original assignee: Civil Engineering Design Academy Of Chang'an University Co ltd; Qingdao Institute Of Traffic Sciences; Qinghai Transportation Investment Co ltd; Changan University
Current assignee: Civil Engineering Design Academy Of Chang'an University Co ltd; Qingdao Institute Of Traffic Sciences; Qinghai Transportation Investment Co ltd; Changan University
Priority date: 2021-02-02
Filing date: 2021-02-02
Publication date: 2021-06-04

Abstract

The composite geomembrane salt-separating water-blocking partition layer structure related by the invention adopts the combination of two cloth films and one plastic drainage plate to separate water and salt which migrate upwards and effectively discharge the water and salt outside the roadbed, thereby preventing diseases such as salt expansion, slurry overflow and mud bleeding of the roadbed, greatly improving the overall stability of the roadbed and better reducing the height of the roadbed. The two cloth-one film is a synthetic fiber waterproof cloth fabric formed by two layers of filament woven cloth and one layer of High Density Polyethylene (HDPE) geomembrane. The plastic drainage plate is formed by wrapping non-woven geotextile (filter membrane) outside continuous plastic core plates with different cross-sectional shapes. The composite geomembrane salt-separating water-blocking partition layer structure is simple in structure, easy to operate, convenient to construct and low in manufacturing cost, has better economic benefits and good social effects on the treatment of the highway subgrade in the saline land area, and has wide application prospects in the fields of highways, railways, civil aviation airport runways, oil pipelines and the like.

Description

Composite geomembrane salt-separating water-blocking partition layer structure

Technical Field

The invention relates to highway subgrade engineering, in particular to a roadbed replacement and filling partition layer structure in the highway subgrade engineering in a saline soil area.

Background

The composite geomembrane is a synthetic fiber waterproof cloth-shaped fabric formed by combining two cloth-one films and a plastic drainage plate, wherein the two cloth-one films are formed by weaving two layers of filament yarns into cloth and sandwiching one layer of polyethylene (HDPE) geomembrane. The plastic drainage plate is formed by wrapping non-woven geotextile (filter membrane) outside continuous plastic core plates with different cross-sectional shapes.

The saline soil as a special roadbed filling has a plurality of engineering hidden dangers: under the repeated crystallization action of sulfate in the saline soil, the volume change is caused, the soil body structure is damaged, and the engineering diseases such as subgrade settlement, slope collapse, pavement stability reduction and the like are caused due to corrosion, salt expansion, frost heaving, slurry turning and the like; the saline soil contains a large amount of sulfate and chloride, has great corrosivity on bridge and culvert structures, and seriously threatens the durability and the safety of the bridge and culvert structures. The highway engineering is a strip engineering, the spanning range is wide, and the geological conditions of the saline soil area are complex and changeable.

The arrangement of the partition layer fully meets the actual engineering requirements, the migration rule of capillary water in different embankment fillers is researched according to actual factors such as embankment fillers of specific road sections, the height of a roadbed, the distribution of underground water and the like, and the reasonable partition layer is arranged according to the migration rule. Saline soil district highway subgrade sets up the partition layer and can effectively block capillary water and carry the salinity and rise, prevents that moisture and salinity from getting into lower road bed or even upper road bed to avoid road bed or road surface to suffer destruction.

In order to prevent roadbed salinization and secondary salinization, the prior art comprises the processes of improving the height of a roadbed, arranging a water-permeable soil partition layer, an asphalt mortar partition layer, a geotechnical fiber material partition layer and the like. The different forms of partition layers have a great influence on the overall stability of the roadbed. Therefore, the selection of a reasonable partition layer structure is one of the key factors for ensuring the stability of the roadbed in the saline soil area.

The gravel (crushed) partition layer is suitable for roads more than two levels newly built in areas with high underground water level or strong saline soil with much rainfall. The thickness of the partition layer is preferably 30-50 cm, the maximum particle size of gravel (crushed) is less than 50mm, the content of powder particles is less than 5%, the reverse filter layer is preferably made of geotextile with a penetration function, or medium and coarse sand, the mud content is not more than 3%, and the thickness is 10-15 cm.

The aeolian sand or river sand partition layer is suitable for building and reconstructing roads at the edges of deserts and downstream sections of river channels, which lack gravel materials and are rich in sand. The thickness of the partition layer depends on the conditions of roadbed soil quality, hydrology, geology and the like and the factors of the particle composition of the material of the partition layer and the like, and is determined according to the calculation of the rising height of capillary water, the minimum thickness is not less than 60cm, the content of powder particles in sandy soil is less than 5 percent, and the salt content is in accordance with the specification of 0-0.8 m (thickness of a road bed) of the 7.11.7 level in the table of JTGD30-2015 Highway roadbed design specification. The degree of compaction should comply with the specifications in Table 3.3.4 of JTGD 30-2015. The two sides of the sand soil partition layer should be covered with gravel (sand) soil, and the width of the gravel (sand) soil is not less than 30 cm.

The composite geomembrane partition layer is suitable for building highways above secondary high-grade pavements in medium, strong or over-saline soil areas. It has soft texture, good combination with soil, good toughness and wear resistance. The geotextile in the composite geomembrane is formed by weaving filament yarns and non-woven fabrics and pressing PE plastics at high temperature, has good anti-permeability, corrosion resistance and microbial erosion resistance, and has the characteristics of ageing resistance, freezing resistance and high tensile strength. The composite geomembranes are of various varieties and can be generally divided into two cloth films and one film when used as a partition layer. The two cloth-film partition layers may not be provided with upper and lower protective layers, and the one cloth-film partition layer may be provided with a protective layer only on one side with the film. But the upper part and the lower part of the composite geomembrane partition layer paved in the fine soil are respectively provided with a sand or gravel drainage layer with the thickness not less than 20 cm. The maximum grain diameter of the drainage layer is 60mm, and the content of powder particles is not more than 15%. The bottom embedding depth of the lower drainage layer is larger than the maximum local freezing depth.

The geomembrane partition layer is suitable for newly building or reconstructing roads in strong and over-saline soil areas, wherein the polyethylene impermeable film and the polypropylene drench membrane woven cloth are only suitable for being used in three-level and four-level roads or drainage engineering. The geomembrane partition layer is provided with an upper protective layer and a lower protective layer, the protective layer is made of sand or soil sand containing fine grains, and the content of powder particles is less than 15%. If the partition layer is arranged in coarse-grained soil, the thickness of the protective layer can be 8-10 cm; if it is set in fine soil, the protecting layer can play the role of draining water, and its thickness should be not less than 20 cm.

Although the structure of the partition layer can improve the stability of the roadbed in the saline land area to a certain extent, the structure of the partition layer aims at the specific type of highway engineering, and has the advantages of multiple material varieties, complex process and insignificant salt and water separation effects.

Disclosure of Invention

Aiming at the problems of single performance, insignificant effect and the like of the prior art, the invention provides a novel comprehensive partition layer structure, which aims to effectively partition water and salt which migrate upwards in a form of combining two cloth membranes and a plastic drainage plate and discharge the water and the salt out of a roadbed, thereby greatly improving the overall stability of the roadbed.

The composite geomembrane related by the invention is composed of two cloth membranes and a plastic drainage plate. The plastic drainage plate is transversely arranged, and the filament woven two-cloth one-film composite geotextile is laid on the plastic drainage plate. The two cloth-one film is a synthetic fiber waterproof cloth-shaped fabric formed by two layers of filament woven composite geotextile and one layer of High Density Polyethylene (HDPE) geomembrane; the plastic drainage plate is formed by wrapping non-woven geotextile (filter membrane)) outside continuous plastic core plates with different cross-sectional shapes, and the capillary water of the subgrade underground with salt is guided to the grooves along the inclined plane and is discharged to the outside.

The model of the plastic drainage plate is SPB-B-FF-250-25, the product code is SPB, B is the beating depth and the flat-laying length, and the values are as follows: the width is 250mm and the thickness is 25 mm.

The filament woven composite geotextile is in a model number of PP50-4-250, wherein PP is polypropylene and has the following values: the radial nominal breaking strength is 50kN/m, the breadth is 4-6m, and the mass per unit area is 250 g/square meter; the thickness of the HDPE high-density polyethylene hot-pressing composite geomembrane is 3-4 mm; the unit area mass of the composite geotextile is more than or equal to 900 g/square meter.

The arrangement of the composite geomembrane salt-separating water-blocking partition layer structure comprises the following steps:

step 1. cleaning of the foundation bed

Inspecting the foundation bed and removing various impurities which hinder the laying of the composite geotextile, wherein in order to facilitate the drainage of water and salt, the roadbed is provided with a bidirectional transverse slope not less than 2 percent but not more than 5 percent at most;

step 2, laying plastic drainage plates

The plastic drainage plates are arranged at intervals of 2.5 meters along the longitudinal direction of the roadbed, penetrate through the whole road width and extend out of the roadbed by a plurality of meters, so that the plastic drainage plates can be conveniently implemented together with the edge-covered geotextile and the comprehensive drainage system.

Step 3, laying two-cloth one-film composite geotextile

And (3) laying filament woven two-cloth one-film composite geotextile on the plastic drainage plate. The transverse lap joint between each two frames is not less than 20cm, and a welding form and a welding line are adopted. After one piece of cloth is laid, the longitudinal connection also adopts welding, the lap joint length is not less than 50cm, and two welding lines are formed.

Compared with the prior art, the invention has the beneficial effects that: the novel comprehensive partition layer structure can be applied to various levels of highways with different salinization degrees by combining the two cloth films and the plastic drainage plates, and the composite geotextile has the characteristics of high strength, good ductility, large deformation modulus, acid and alkali resistance, corrosion resistance, aging resistance, good seepage resistance, softness, easiness in processing and the like, and meets the requirements of seepage prevention, water resistance, salt separation and the like in roadbed engineering. The structure of the partition layer is simple in arrangement, easy to operate and convenient to construct, has important practical significance on the treatment of the highway subgrade in the saline soil area, has wide application prospect, can greatly improve the overall stability of the subgrade and well reduce the height of the subgrade, and has effect and applicability obviously superior to those of the prior art.

Drawings

Fig. 1 (see the seventh, attached drawing in the description) is a cross-sectional view of a roadbed.

Fig. 2 (see the seventh section and the attached drawing in the specification) is a plan layout view of a composite geomembrane partition layer.

Fig. 3 (see the seventh, attached drawings in this section) is a cross-sectional view of a plastic drain board.

FIG. 4 (see the seventh section, attached figure of the specification) is a cross-sectional view of two cloth and one film.

In the figure: 1-plastic drainage plate, 2-toe line, 3-left and right road shoulders, 4-center line, 5-composite geomembrane, 6-edge-covered geotextile, 7-surface-cleaning thickness, 8-roadbed filler, 9-SPB-B-FF-250-25 type drainage plate, 10-reverse filter layer, 11-PP50-4-250 type filament woven composite geotextile and 12-3mm thick PE high-density polyethylene hot-pressing composite geomembrane.

Detailed Description

The invention is further illustrated by the following figures and examples.

As shown in fig. 1, the partition layer position takes the road centerline 4 as the axial direction, and both ends extend through the road shoulder to the outside of the toe line. The structure is as follows: the plastic drainage plates are arranged at intervals of 2.5 meters along the longitudinal direction of the roadbed by 25cm (width) multiplied by 2.5cm (thickness), the length is continuously arranged by 100 meters, and the filament woven two-cloth one-film composite geotextile is laid on the drainage plates.

As shown in fig. 2, the present embodiment is a composite geomembrane salt-barrier water-blocking partition layer structure, the roadbed length is 330m, and the average filling height is 3.0 m. After the surface soil 7 is removed, the non-saline soil filler 8 is filled, the roadbed is filled to a large height, salt is prevented from rising as soon as possible, and a separation layer is arranged at a position 50cm higher than the ground.

Claims

1. Compound geomembrane separates salt and blocks water and cuts off layer structure, its characterized in that: one consists of two cloth-one membranes (1) and a plastic drainage plate (2).

2. Two plastic plate rows of channels are transversely arranged, and filament is laid on the plastic plate rows of channels to weave two cloth-one film composite geotextiles.

3. The geomembrane salt-and water-blocking partition layer structure according to claim 1, wherein: the two cloth-one films are synthetic fiber waterproof cloth-shaped fabrics formed by two layers of filament woven fabrics (3) and a layer of high-density polyethylene (HDPE) hot-press molding film.

4. The composite geomembrane salt-and water-blocking partition layer structure according to claim 1, wherein: the plastic drainage plate (4) is formed by wrapping non-woven geotextile (filter membrane) outside continuous plastic core plates with different cross-sectional shapes.

5. The method for arranging the composite geomembrane salt-and water-blocking partition layer structure according to claim 1, comprises the following steps: cleaning a foundation bed, laying a plastic drainage plate and two cloth-one film composite geotextiles.

6. Firstly, inspecting the foundation bed and removing various impurities which hinder the safety of the composite geotextile, and setting an outward transverse slope of not less than 2% but not more than 5% at most for facilitating the drainage of water and salt.

7. And secondly, plastic drainage plates are transversely arranged at intervals of 2.5 meters, and filament woven two-cloth one-film composite geotextile is laid on the plastic drainage plates.

8. And thirdly, transversely overlapping all the geotextile by 20cm, and adopting a welding mode.

9. And the longitudinal connection of one welding seam after one longitudinal piece is spread is also welded, the lap joint length is 50cm, and two welding seams are formed.