WO2022047643A1

WO2022047643A1 - Environmentally-friendly composite bypass seepage-prevention flexible vertical isolation system, and installation method

Info

Publication number: WO2022047643A1
Application number: PCT/CN2020/112951
Authority: WO
Inventors: 孙新坡; 毕钰璋; 傅贤雷; 庹先国; 伍浩良; 郭毅
Original assignee: 四川轻化工大学; 必照岩土科技(南京)有限公司
Priority date: 2020-09-02
Filing date: 2020-09-02
Publication date: 2022-03-10
Also published as: ZA202109988B

Abstract

Disclosed are an environmentally-friendly composite bypass seepage-prevention flexible vertical isolation system, and an installation method. Said isolation system comprises bypass seepage-prevention members (1) for retarding pollutants in underground water and soil; each bypass seepage-prevention member (1) comprises a prefabricated fiber-reinforced cement-based material or a carbonized magnesium oxide-based material, closed bolts (3) having two reserved openings are formed on the surface of the bypass seepage-prevention member (1), one flexible seepage-prevention wall body (2) is sandwiched between the two bypass seepage-prevention members (1), and the flexible seepage-prevention wall body (2) is composed of a rectangular high-density polyethylene geomembrane. The system can solve the leakage problem caused by poor contact between a geomembrane and a water-impermeable layer at the bottom of a tank, and can meet the requirement of maintaining the seepage-prevention property in extreme earthquake or large geological activity; the system uses an environmentally-friendly material, magnesium oxide, accelerates the formation of members by using a carbonization method, and can comprehensively use an environmentally-friendly material, absorb carbon dioxide, and efficiently produce highly-ductile bypass seepage-prevention materials.

Description

An environment-friendly composite anti-circumferential flexible vertical isolation system and installation method

technical field

The invention relates to the technical field of ecological environment restoration, in particular to an environment-friendly composite type anti-circumferential flexible vertical isolation system and an installation method.

Background technique

With the rapid development of industrialization in our country, the damage to the environment is also becoming more and more serious. In particular, some chemical and mining enterprises have not taken anti-seepage measures for existing solid waste storage yards, mine heap leaching yards, tailings ponds, etc., resulting in toxic and harmful substances harming the ecological environment through various ways, polluting soil and groundwater bodies, and seriously. Affect people's normal life and physical health.

With the advancement of technology, the anti-seepage problems of storage yards, landfills and tailings ponds of chemical and mining enterprises have been effectively solved. Some vertical anti-seepage technologies, such as grouting curtains, stirring piles, steel sheet piles and vertical slotting and plastic laying, have been applied in engineering practice. The vertical slotting plastic laying technology uses high-density polyethylene geomembrane as the anti-seepage material, and is vertically inserted into the underground impermeable layer to form a flexible vertical anti-seepage system. This process technology has low permeability coefficient, good chemical stability and continuity, adaptability The advantages of strong deformation ability and so on. However, in this process, the connection between the geomembrane and the base soil or bedrock of the impermeable layer at the bottom of the tank often cannot be well treated, which is easy to cause local leakage. The present invention can solve such leakage problems and can meet the requirements of extreme earthquakes Or under large-scale geological activities, the anti-seepage system can still meet the anti-seepage requirements.

SUMMARY OF THE INVENTION

Based on the technical problems existing in the background technology, the present invention proposes an environment-friendly composite anti-circumferential flexible vertical isolation system, including an anti-circumferential component for blocking pollutants in groundwater and soil, and the anti-seepage component includes: A prefabricated fiber-reinforced cement-based material or a magnesium carbide-based material, the surface of the anti-seepage member is formed with two reserved closed bolts, and the two anti-seepage members clamp each other with the same flexible anti-seepage wall. The anti-seepage wall is composed of rectangular high-density polyethylene geomembrane.

Preferably, the material mixing ratio of the prefabricated anti-seepage member is Type I, wherein the material mixing ratio of Type I is: rapid self-hardening cement, magnesium oxide, natural sand, fly ash, water and polycarboxylate water-reducing The mass ratio of the agent is: 0.94-1:0-0.06:0.6-0.8:1.2-2.2:0.56:0.07-0.12, wherein the I-type prefabricated anti-seepage member is mixed with fibers, and the fibers account for 0.8-1.2 of the total volume %.

Or the material mixing ratio of the prefabricated anti-seepage member can be type II: the mass ratio of magnesium oxide, fly ash, water, sodium hexametaphosphate and polycarboxylate superplasticizer is: 5-7:3-5: 0.52: 0.06-0.12: 0.007-0.008, wherein the type II prefabricated anti-seepage structure is mixed with fibers, wherein the fibers account for 0.8-1.2% of the total volume.

Preferably, the size ratio of the length, width and height of the flexible anti-seepage wall is: 10:0.5-1.5:0.4-1.2, the two closing bolts are stainless steel stud bolts, and the bolt size is M10-M30 Standard bolts.

Preferably, the seepage prevention member is composed of two prefabricated cuboid members, the rectangular high-density polyethylene geomembrane is embedded between the two prefabricated members, and the seepage prevention member is embedded in the underground water impermeable layer.

Preferably, the cement is fast-hardening aluminate cement, the magnesia is light magnesia, the magnesia is industrial grade light magnesia with a mass content of 70-88%, and the natural sand is River sand or basalt sand or gabbro sand whose maximum particle size is less than 0.5mm, the fly ash is domestic 1-2 grade fly ash, the water is industrial tap water, and the water reducing agent is polycarboxylate Water reducing agent, the fibers can be polyvinyl alcohol and polypropylene fibers in synthetic fibers, sugarcane fibers or acetate fibers in artificial fibers, and cellulose fibers in natural fibers.

Preferably, in the I-type prefabricated anti-seepage member, the prefabrication method is to mix the rapid self-hardening cement, magnesia, natural sand, fly ash, water and polycarboxylate water-reducing agent evenly, and then add claim 5 The specific fibers are rapidly stirred and poured into the prefabricated component mold of claim 3, cured for 6 hours at 20-25°, and released from the mold, followed by curing for 2 days.

Preferably, in the type II prefabricated anti-seepage member, the prefabrication method is to stir magnesium oxide, fly ash, water, sodium hexametaphosphate and polycarboxylate water-reducing agent evenly, add the specific fiber according to claim 5 to quickly Stir and pour into the prefabricated component mold according to claim 3, cure for 6h at 20-25°, release molding, and then carbonize and cure in the carbonization box for 1-12h, the carbon dioxide concentration in the carbonization box is 60-98%, and the curing atmospheric pressure value 1.2-5.8MPa.

Preferably, the sodium hexametaphosphate and the polycarboxylate superplasticizer are respectively stirred in water to form a mixed solution 1 and a mixed solution 2, the mixing temperature of the mixed solution 1 is 65-110°, and the stirring temperature of the mixed solution 2 is 10 -20°.

An installation method of an environment-friendly composite anti-seepage flexible vertical isolation system, comprising the following steps:

S1: Prefabricated anti-seepage components: According to the requirements of the actual polluted site, prefabricated anti-seepage components of the corresponding number and length, and cut the corresponding wide HDPE geomembrane;

S2: Making an anti-seepage unit: Insert a single vertical HDPE geomembrane into two prefabricated anti-seepage components, and connect the prefabricated anti-seepage components to the vertical HDPE geomembrane with double-ended threaded bolts. The membrane is fixed to form a composite anti-seepage flexible vertical isolation unit;

S3: Slotting: Slotting vertically along the periphery of the construction contaminated site, excavating the bottom of the slot into the underground impermeable layer, and using domestic commercial bentonite mud with a mass ratio of 2% to protect the wall during the vertical slotting process;

S4: Forming an anti-seepage system: insert the anti-seepage wall unit obtained in step S2 into the vertical slot in the vertical slotted retaining wall mud, and the anti-seepage support part is placed in the vertically slotted slot end;

S5: Repeat step S4 to make each anti-seepage unit in close contact, and the high-density polyethylene geomembrane of the anti-seepage unit is connected by hot-melt butt joint;

S6: Grouting: inject the corresponding bentonite slurry into the tank to cover the joint of the anti-winding member by pumping;

S7: Backfill: Backfill one or a mixture of sand and clay into the trench to remove the retaining wall mud.

For the type I prefabricated anti-seepage member, the casting material of the anti-seepage member is a high-ductility cement-based material, and the high-ductility cement-based material includes the following components according to mass percentage:

and PVA fibers,

Among them, the volume content of PVA fiber is 0.8-1.2% of the total volume of the high ductility cement slurry.

As a preferred solution, the mass ratio of the rapid self-hardening cement, magnesium oxide, natural sand, fly ash, water and polycarboxylate superplasticizer is: 100:6:80:220:56:12.

As a preferred solution, the cement is fast-hardening aluminate cement, the average particle size of the natural sand is 0.75mm, the fly ash is domestic 1-2 grade fly ash, and the magnesia is lightweight Magnesium oxide, the water reducing agent is a polycarboxylate water reducing agent.

As a preferred solution, the magnesium oxide is industrial-grade light magnesium oxide with a mass content of 70-88%, and the source of the sand particles is broken sand of gabbro sand.

As a preferred version, the crushed gabbro sand is prepared by rolling by the following method:

The gabbro tailings sand is processed by a high-voltage pulse crusher, which can form a high voltage of 90-200kV, and then discharge to the rock samples in the water through the high-voltage working electrode in a very short time. The rock is split between the body and different phases, and the fragmented rock is sieved with a 35-mesh standard sieve for use.

For the type II prefabricated anti-circumferential component, the casting material of the anti-circumferential component is a high-ductility magnesium carbide-based material, and the high-ductility magnesium carbide-based material includes the following components according to mass percentage:

and PVA fibers,

Wherein, the volume content of the PVA fiber is 0.8-1.0% of the total volume of the high ductility magnesium carbide-based material.

As a preferred solution, the mass ratio of magnesium oxide, fly ash, water, sodium hexametaphosphate and polycarboxylate superplasticizer is: 700:500:56:12:0.8.

As a preferred solution, the magnesium oxide is 70-88% light industrial grade light magnesium oxide, the fly ash is domestic 1-2 grade fly ash, and the water reducing agent is a polycarboxylate water reducing agent , the carbon dioxide concentration used to accelerate carbonization is 92%, and the curing atmospheric pressure value is 3.5MPa.

As a preferred solution, in the process of preparing the high-ductility magnesium carbide-based material, the water is stirred three times, the first time is mixed with sodium hexametaphosphate separately, the second time is mixed with polycarboxylate water-reducing agent alone, and the third time is mixed with oxidizer The magnesium and fly ash mixture is mixed, wherein the mass ratio of water added in the first stirring, the second stirring and the third stirring is 2:2:3.

For the fabricated anti-seepage unit, it consists of two symmetrical prefabricated anti-seepage members and a pair of vertical high-density polyethylene geomembrane, the high-density polyethylene geomembrane is inserted into the two prefabricated anti-seepage components, and fastened with threaded bolts.

As a preferred solution, the size ratio of the length (L), width (W) and height (H) of the prefabricated anti-seepage member is: 10:0.5-1.5:0.4-1.2.

As a preferred solution, the length of the anti-seepage member is 2 meters, the width is 10 cm, the height is 8 cm, and the longitudinal length of a single sheet of the high-density polyethylene geomembrane is 2.2 meters.

As a preferred solution, the high-density polyethylene geomembrane adopts a double-slit hot-melt welding process. The density polyethylene geomembrane that is to be cut is connected by hot-melt butt joint, and the two sides that need to be overlapped are hot-melted. The hot-melt temperature The temperature is 100-150°C. After reaching the temperature, the butt joint is carried out quickly. The butt joints on both sides have hollow cavities, and the hollow cavities have compressed air. The butt joints on the left and right sides of the hollow cavity are welding seams. Welding is performed at the welding seam. The temperature is 450-480 ℃, and the welding process needs to ensure the integrity of the welding point.

Beneficial effects: Compared with the existing slotted plastic laying technology, the environmentally friendly composite anti-seepage flexible vertical isolation system of the embodiment of the present invention has the following advantages: the system can solve the problem of poor contact between the geomembrane and the impermeable layer at the bottom of the slot. It can meet the requirements of maintaining impermeability under extreme earthquakes or large-scale geological activities. It adopts the environmentally friendly material magnesium oxide, and uses the carbonization method to accelerate the formation of components, which can achieve comprehensive utilization of environmentally friendly materials, absorption of carbon dioxide, and efficient output and anti-winding. The infiltrating material has the positive effect of high ductility.

Description of drawings

Fig. 1 is the result diagram of tensile deformation and permeability coefficient under the action of tensile force of type I and type II environmental protection composite anti-winding members of the present invention;

Figure 2 is a diagram showing the relationship between the tensile amount and the tensile strength of the I-type and II-type environmental protection composite anti-winding members of the present invention, under the condition of simulated earthquake-induced tensile failure;

Fig. 3 is a vertical partition wall system diagram of the preparation and installation method of an environmentally friendly composite anti-seepage flexible vertical isolation system proposed by the present invention;

4 is a schematic cross-sectional view of the site application of the vertical isolation wall system of the preparation and installation method of an environmentally friendly composite anti-seepage flexible vertical isolation system proposed by the present invention.

In the picture: 1 anti-seepage components, 2 flexible anti-seepage walls, 3 closed bolts.

detailed description

The present invention will be further explained below in conjunction with specific embodiments.

Referring to Figures 1-4, the present invention proposes an environment-friendly composite anti-seepage flexible vertical isolation system, including anti-seepage components used to block groundwater and pollutants in the soil, and the anti-seepage components include prefabricated components. Fiber-reinforced cement-based material or magnesium carbide-based material, the surface of the anti-seepage member is formed with two closed bolts reserved, and the two anti-seepage members clamp each other with the same flexible anti-seepage wall, and the flexible anti-seepage member is The wall is composed of rectangular high-density polyethylene geomembrane.

The type I and type II prefabricated anti-seepage components include the following components according to mass percentage:

Type I prefabricated anti-seepage components:

And PVA fiber, the volume content of PVA fiber is 0.8-1.2% of the total volume of high ductility cement slurry.

Type II prefabricated anti-seepage components:

As well as PVA fibers, the volume content of PVA fibers is 0.8-1.0% of the total volume of the high ductility magnesium carbide-based material.

The process of preparing the I-type composite anti-seepage member: Mix the solid materials (aluminate cement, magnesia, natural sand, fly ash) evenly, add water for the first stirring, and then add PVA fiber and water for the first time. Stir for the second time to obtain high ductility fiber slurry, and pour the prepared high ductility fiber slurry into a mold through a pouring device to form a prefabricated component.

The process of preparing the type II composite anti-seepage member: the first stirring of sodium hexametaphosphate and water, the stirring temperature is set to 65 °, to form mixed solution 1, and then the polycarboxylate water reducing agent and water are mixed for the first time. Second stirring to form mixed solution 2, and finally the solid material (magnesium oxide and fly ash), solution 1 and solution 2 are mixed and stirred for the third time to obtain high ductility fiber slurry, poured into the mold, and waited for 6 hours for carbonization Curing to form prefabricated components.

Example analysis

The following tests verify that an environment-friendly composite anti-seepage flexible vertical isolation system of the embodiment of the present invention has good anti-seepage characteristics and high ductility.

Example 1

The process of preparing the I-type composite anti-seepage member: Mix the solid materials (aluminate cement, magnesia, natural sand, fly ash) evenly, add water for the first stirring, and then add PVA fiber and water for the first time. Stir for the second time to obtain high ductility fiber slurry, and pour the produced high ductility fiber slurry into the mold through pouring equipment to form prefabricated components. The length, height and thickness of the prefabricated components are respectively 2m*10cm*8m.

In this embodiment, the I-type composite anti-seepage member includes the following components according to mass percentage:

The volume content of fiber PVA is 0.8-1.2% of the total volume of high ductility cement slurry.

Example 2

The process of preparing the prefabricated anti-seepage member is the same as that in Example 1, the difference is:

Example 3

Example 4

The process of preparing the type II composite anti-seepage member: the first stirring of sodium hexametaphosphate and water, the stirring temperature is set to 65 °, to form mixed solution 1, and then the polycarboxylate water reducing agent and water are mixed for the first time. Second stirring to form mixed solution 2, and finally the solid materials (magnesium oxide and fly ash), solution 1 and solution 2 are mixed and stirred for the third time to obtain high ductility fiber slurry, which is poured into the mold.

In this embodiment, the type II composite anti-seepage member includes the following components according to mass percentage:

The volume content of the fiber PVA is 0.8-1.0% of the total volume of the high ductility magnesium carbide-based material.

In addition, in this Example, the carbonization time was 1 hour, and the carbonization pressure was 2.5 MPa.

Example 5

The process of preparing the prefabricated anti-seepage member is the same as that in Example 4, the difference is that: in this example, the carbonization time is 6 hours, and the carbonization pressure is 2.5MP.

Example 6

In addition, in this Example, the carbonization time was 1 hour, and the carbonization pressure was 2.5 MP.

Example 7

The process of preparing the prefabricated anti-seepage member is the same as that in Example 6, except that: in this example, the carbonization time is 6 hours and the carbonization pressure is 2.5MP.

Anti-seepage test

Test process: The long-term performance and durability performance test method standard of ordinary concrete with the national standard GB-T50082-2009 was used for the test.

The test results are shown in Figure 1. The impermeability requirement (10 ^-9 m/s) can be met without cracking, which can meet international standards and be used to block the migration of pollutants and prevent seepage in polluted sites and mining areas.

It can be seen from Figure 1 that increasing the content of magnesium oxide can effectively reduce the permeability coefficient of the I prefabricated anti-seepage structure, and as the crack width increases, the effect is more obvious. The mechanism is that magnesium oxide can be hydrated to form swelling body filling. Cracks and cracks can continue to be hydrated to form hydration products such as hydrated magnesium silicate, thereby reducing the permeability coefficient. 1.

For type II prefabricated anti-seepage components, increasing the content of magnesium oxide and increasing the carbonization time can reduce the permeability coefficient.

High ductility test

Test process: The test was carried out using the national standard GB/T 50081-2002 standard for the test method for mechanical properties of ordinary concrete.

The test results are shown in Figure 2. The results show that both the type I and type II anti-seepage components have high ductility similar to metal materials, and the maximum deformation can reach 6.2%.

For the I-type anti-seepage member, increasing the content of magnesium oxide can enhance the tensile strength of the member, slightly affect the tensile amount, and effectively control the crack width, that is, the tensile strength is ranked as Example 3 > Example 2 >Example 1.

For type II prefabricated components, increasing the content of magnesium oxide can improve the tensile strength of the prefabricated components and the tensile strength of the prefabricated components; increase the carbonization time of the prefabricated components and increase the carbon dioxide absorption, that is, improve the environmental protection benefits, but weaken the weak prefabricated components. increase the tensile strength of the prefabricated components, that is, the tensile strength is arranged as Example 4 > Example 5 > Example 6 > Example 7; the tensile strength is arranged as Example 5 > Example 7>Example 4>Example 6.

The above description is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited to this. The equivalent replacement or change of the inventive concept thereof shall be included within the protection scope of the present invention.

Claims

An environmentally friendly composite anti-circumferential flexible vertical isolation system, comprising an anti-seepage member (1) for blocking pollutants in groundwater and soil, wherein the anti-seepage member (1) comprises a prefabricated anti-seepage member (1). The fiber-reinforced cement-based material or the magnesium carbide-based material, the surface of the anti-seepage member (1) is formed with two closed bolts (3) reserved, and the two anti-seepage members (1) clamp each other with the same flexible anti-seepage A seepage wall (2) is provided, wherein the flexible anti-seepage wall (2) is composed of a rectangular high-density polyethylene geomembrane.
An environmentally friendly composite type anti-circumferential flexible vertical isolation system according to claim 1, characterized in that, the material mixing ratio of the prefabricated anti-seepage member (1) is type I, wherein the material mixing ratio of type I is It is: the mass ratio of rapid self-hardening cement, magnesium oxide, natural sand, fly ash, water and polycarboxylate superplasticizer: 0.94-1: 0-0.06: 0.6-0.8: 1.2-2.2: 0.56: 0.07 -0.12, wherein the type I prefabricated anti-infiltration component (1) is mixed with fibers, and the fibers account for 0.8-1.2% of the total volume; or the prefabricated anti-infiltration component (1) The material mixing ratio can be type II: The mass ratio of magnesium oxide, fly ash, water, sodium hexametaphosphate and polycarboxylate superplasticizer is: 5-7:3-5:0.52:0.06-0.12:0.007-0.008, among which type II prefabricated anti-seepage prevention The component (1) is mixed with fibers, wherein the fibers account for 0.8-1.2% of the total volume.
The environment-friendly composite anti-seepage flexible vertical isolation system according to claim 1, characterized in that the size ratio of the length, width and height of the flexible anti-seepage wall (2) is: 10:0.5- 1.5:0.4-1.2, the two closing bolts (3) are stainless steel stud bolts, and the bolt size is M10-M30 standard bolts.
The environment-friendly composite anti-seepage flexible vertical isolation system according to claim 1, characterized in that, the anti-seepage member (1) is composed of two prefabricated cuboid members, and the rectangular high-density polyethylene The geomembrane is embedded between two prefabricated components, and the anti-seepage component (1) is embedded in the underground impermeable layer.
The environment-friendly composite anti-seepage flexible vertical isolation system according to claim 1, wherein the cement is fast-hardening aluminate cement, the magnesium oxide is light magnesium oxide, and the oxidized Magnesium is industrial grade light magnesia with a mass content of 70-88%, the maximum particle size of the natural sand is less than 0.5mm river sand or basalt sand or gabbro sand, and the fly ash is domestic 1-2 grade fly ash, the water is industrial tap water, the water reducing agent is a polycarboxylate water reducing agent, and the fibers can be polyvinyl alcohol and polypropylene fibers in synthetic fibers, or sugarcane in artificial fibers Cellulosic fibres in fibre or acetate and natural fibres.
The environment-friendly composite type anti-circumferential flexible vertical isolation system according to claim 1, characterized in that, in the I-type prefabricated anti-circumferential components, the prefabrication method is to combine rapid self-hardening cement, magnesium oxide, natural After the sand, fly ash, water and polycarboxylate superplasticizer are evenly stirred, the specific fibers described in claim 5 are added and poured into the prefabricated component mould described in claim 3 with rapid stirring, and the mold is released for 6 hours under curing at 20-25°. , followed by 2 days of curing.
The environment-friendly composite type anti-circumferential flexible vertical isolation system according to claim 1, wherein, in the type II prefabricated anti-circumferential components, the prefabrication method is to mix magnesium oxide, fly ash, water, six Sodium metaphosphate and polycarboxylate water-reducing agent are stirred evenly, the specific fibers described in claim 5 are added, and the specific fibers described in claim 5 are rapidly stirred and poured into the prefabricated component mold described in claim 3, and cured for 6 hours at 20-25 °. Internal carbonization curing for 1-12h, the carbon dioxide concentration in the carbonization box is 60-98%, and the curing atmospheric pressure value is 1.2-5.8MPa.
The environmental protection composite type anti-circumferential flexible vertical isolation system according to claim 6 or 7, wherein the sodium hexametaphosphate and the polycarboxylate water-reducing agent are stirred in water to form mixed solutions 1 and 1 respectively. Mixed solution 2, the stirring temperature of the mixed solution 1 is 65-110°, and the stirring temperature of the mixed solution 2 is 10-20°.
An installation method of an environment-friendly composite anti-seepage flexible vertical isolation system, characterized in that it comprises the following steps:

S1: Prefabricated anti-seepage components: According to the requirements of the actual polluted site, prefabricated anti-seepage components of the corresponding number and length, and cut the corresponding wide HDPE geomembrane;

S2: Making an anti-seepage unit: Insert a single vertical HDPE geomembrane into two prefabricated anti-seepage components, and connect the prefabricated anti-seepage components to the vertical HDPE geomembrane with double-ended threaded bolts. The membrane is fixed to form a composite anti-seepage flexible vertical isolation unit;

S3: Slotting: Slotting vertically along the periphery of the construction contaminated site, excavating the bottom of the slot into the underground impermeable layer, and using domestic commercial bentonite mud with a mass ratio of 2% to protect the wall during the vertical slotting process;

S4: Forming an anti-seepage system: insert the anti-seepage wall unit obtained in step S2 into the vertical slot in the vertical slotted retaining wall mud, and the anti-seepage support part is placed in the vertically slotted slot end;

S5: Repeat step S4 to make each anti-seepage unit in close contact, and the high-density polyethylene geomembrane of the anti-seepage unit is connected by hot-melt butt joint;

S6: Grouting: inject the corresponding bentonite slurry into the tank to cover the joint of the anti-winding member by pumping;

S7: Backfill: Backfill the trench with sand and clay or a mixture thereof to remove the retaining wall mud.