Sewage pond closed curing treatment method

Abstract

The invention relates to the technical field of building construction, in particular to a sewage pond sealing and curing treatment method. The closed curing treatment method for the sewage pond comprises the steps that the sewage pond is backfilled with muck; rock soil curing agent slurry is injected into the muck in the inner surface layer area of the sewage pond, stirring and curing are conducted, and a cured soil layer is formed; the rock soil curing agent slurry comprises curing agent powder and water, and the curing agent powder comprises the following components in parts by mass: 10-40 parts of cement, 30-60 parts of superfine slag powder, 10-30 parts of fly ash, 5-25 parts of waste gypsum, 5-15 parts of water glass, 5-20 parts of stone powder slag and 5-15 parts of furnace slag. The invention aims to solve the problem that the sewage treatment cost of the sewage pond is relatively high at present.

Description

Technical Field

[0001] The present invention relates to the technical field of building construction, and more particularly, to a method for closed solidification treatment of sewage ponds. Background Art

[0002] In some areas, due to imperfect sewage disposal facilities, a large amount of sewage is discharged into low-lying pond areas. After years of discharge, relatively large-scale sewage ponds have gradually formed. The sewage in the sewage ponds contains various harmful substances, which not only cause direct harm to groundwater and soil, but also affect the entire ecological environment.

[0003] Currently, when treating sewage ponds, most often inorganic or organic gelling materials such as cement and lime are directly added to the sewage ponds for solidification treatment. These gelling materials undergo physical and chemical reactions with water to generate a large amount of hydrated gels (such as calcium silicate hydrate, calcium ferrite hydrate, calcium ferroaluminate hydrate, ettringite, etc.) and minerals (such as calcium carbonate, calcium hydroxide, etc.), thereby solidifying the sewage in these concretion bodies. However, since all the sewage in the sewage pond relies on these gelling materials for solidification, the required material cost is relatively high. It is necessary to add enough cement and lime materials to the water, and rely on the sewage and cement and lime to form a viscous cement slurry to further solidify and harden into a concretion body. Summary of the Invention

[0004] The present invention aims to improve the problem of relatively high sewage treatment cost of current sewage ponds.

[0005] To solve the above problems, the present invention provides a method for closed solidification treatment of sewage ponds, including:

[0006] Backfilling the sewage pond with muck;

[0007] Injecting a geotechnical solidifying agent slurry into the muck in the surface area of the sewage pond and performing stirring and solidification to form a solidified soil layer;

[0008] The geotechnical solidifying agent slurry includes a solidifying agent powder and water. The solidifying agent powder includes the following components in parts by mass: cement: 10 to 40 parts, slag micro-powder: 30 to 60 parts, fly ash: 10 to 30 parts, waste gypsum: 5 to 25 parts, water glass: 5 to 15 parts, stone powder residue: 5 to 20 parts, slag: 5 to 15 parts.

[0009] Optionally, the height of the solidified soil layer is 3 m to 6 m.

[0010] Optionally, before backfilling the sewage pond with muck, it further includes:

[0011] Constructing a closed curtain along the circumferential direction of the sewage pond, the bottom of the closed curtain being located below the bottom of the sewage pond and extending to the clay layer.

[0012] Optionally, the height of the closed curtain entering the clay layer is not less than 3 m.

[0013] Optionally, the closed curtain is formed by mixing the geotechnical curing agent slurry with soil and then stirring and curing.

[0014] Optionally, the position of the closed curtain is 1 m to 2 m away from the edge of the sewage pond.

[0015] Optionally, the closed curtain includes a plurality of curing agent piles, and the plurality of curing agent piles are connected by the method of punching one hole or partial overlapping method.

[0016] Optionally, the backfilling of muck into the sewage pond includes: the water content of the muck does not exceed 25%.

[0017] Optionally, in the geotechnical curing agent slurry, the mass ratio of the curing agent powder to water is 1:(1.5 to 3).

[0018] Optionally, in the solidified soil layer, the mass ratio of the muck to the geotechnical curing agent powder is 1:(0.2 to 0.25).

[0019] The beneficial effects of the fluidized solidified soil layer of the present invention are as follows:

[0020] The present invention adopts a construction method of first backfilling muck into the sewage pond and then injecting geotechnical curing agent slurry into the surface area of the muck, fully stirring the engineering muck, water and geotechnical curing agent into a fluid mixture, and these fluid mixtures form a solidified soil layer body with certain strength, impermeability, water stability and corrosion resistance after solidification. Compared with the related technology of using a single cementitious material to solidify all areas of sewage, the present invention only solidifies the sewage in a certain depth range above the sewage pond, with a small solidification range, and consumes a large amount of construction waste such as engineering muck. The proportion of the geotechnical curing agent does not exceed 30%, greatly reducing the construction and material costs. The muck not solidified in the lower part of the sewage pond can not only seal the sewage between the solidified soil layer and the clay layer, but also serve as a transition soil layer, reducing the mutual influence between the solidified soil layer and the clay layer and preventing the pollution of the clay layer by harmful substances in the solidified soil layer. Description of the Drawings

[0021] Figure 1 It is a schematic structural diagram of the sewage pond before filling soil in the embodiment of the present invention;

[0022] Figure 2 It is a schematic structural diagram of the sewage pond during the process of filling soil in the embodiment of the present invention;

[0023] Figure 3 It is a schematic structural diagram of the sewage pond after filling soil and solidifying in the embodiment of the present invention;

[0024] Figure 4 This is a top view of the closed curtain in the embodiment of the present invention.

[0025] Explanation of reference numerals: 1, sewage pond; 2, closed curtain; 3, solidified soil layer; 4, un-solidified soil layer; 5, clay layer; 6, grouting pump; 7, muck. Specific embodiments

[0026] In order to make the above objects, features and advantages of the present invention more obvious and understandable, the specific embodiments of the present invention will be described in detail below.

[0027] The embodiment of the present invention provides a method for closed solidification treatment of a sewage pond, including: backfilling muck into the sewage pond; injecting a geotechnical solidifying agent slurry into the muck in the surface area of the sewage pond, and stirring and solidifying to form a solidified soil layer. Among them, the geotechnical solidifying agent slurry includes a solidifying agent powder and water, and the solidifying agent powder includes the following components in parts by mass: cement: 10 to 40 parts, slag micro-powder: 30 to 60 parts, fly ash: 10 to 30 parts, waste gypsum: 5 to 25 parts, water glass: 5 to 15 parts, stone powder slag: 5 to 20 parts, slag: 5 to 15 parts.

[0028] Figure 1 This is a schematic structural diagram of the sewage pond 1 before filling soil in the embodiment of the present invention, Figure 2 This is a schematic structural diagram of the sewage pond 1 during soil filling in the embodiment of the present invention, Figure 3 This is a schematic structural diagram of the sewage pond 1 after filling and solidifying soil in the embodiment of the present invention. Refer to Figures 1 to 3 , below the bottom of the sewage pond 1 is a clay layer 5, which is a soil layer composed of clay, has poor water permeability and air permeability, and has excellent anti-seepage performance. The muck 7 in the sewage pond 1 includes the upper solidified soil layer 3 and the lower un-solidified soil layer 4.

[0029] The present invention adopts a construction method of first backfilling muck 7 into the sewage pond 1 and then injecting a geotechnical solidifying agent slurry into the surface area of the muck 7, and fully stirring the engineering muck 7, water and geotechnical solidifying agent into a fluid mixture. These fluid mixtures form a solidified soil layer 3 with certain strength, impermeability, water stability and corrosion resistance after solidification. In the solidified area on the surface of the sewage pond 1, part of the sewage participates in chemical reactions and is consumed, and the other part of the sewage is fixed and wrapped in the solidified soil layer 3 by the solidified gel, preventing the leakage of harmful substances in the sewage to the surrounding environment. In the lower un-solidified soil layer 4, the sewage is gradually consolidated by the clay layer 5 or the filled soil to adsorb the harmful substances in the sewage. Finally, the harmful substances in the sewage pond 1 are all enclosed in the closed space composed of the solidified soil layer 3 and the impermeable clay layer 5, preventing them from penetrating or leaking to the surrounding area.

[0030] Compared with the related technology that uses a single gelling material to solidify the sewage in all areas, the present invention only solidifies the sewage in a certain depth range at the upper part of the sewage pond 1. The solidification range is small, and a large amount of construction waste such as engineering muck 7 is consumed. The proportion of the geotechnical solidifying agent does not exceed 30%, greatly reducing the construction and material costs. The muck 7 that is not solidified in the lower part of the sewage pond 1 can not only seal the sewage between the solidified soil layer 3 and the clay layer 5, but also serve as a transition soil layer, reducing the mutual influence between the solidified soil layer 3 and the clay layer 5 and preventing the pollution of the clay layer 5 by harmful substances in the solidified soil layer 3.

[0031] The geotechnical solidifying agent in the present invention is composed of various industrial solid wastes (slag powder, fly ash, waste gypsum, water glass, stone powder slag, slag, etc.). These solid wastes all contain minerals such as silicon, aluminum, and calcium with different degrees of activity. Under the excitation of additives, the mineral activities in various industrial solid wastes can be maximally stimulated to participate in chemical reactions. When the proportions of various industrial solid wastes reach the optimal proportion, the active silicon, aluminum, calcium and other minerals in these solid wastes, on the one hand, undergo hydration reactions with water to generate hydrated gel minerals and other crystal minerals; on the other hand, they can react chemically with the active minerals in clay minerals to generate hydrated gel minerals and other crystal minerals.

[0032] Therefore, compared with traditional cement materials, the active minerals in these industrial solid wastes and the minerals whose activities are stimulated not only undergo chemical reactions with water to generate hydrated gel minerals (such as hydrated calcium silicate, hydrated calcium aluminate, hydrated calcium ferrite, ettringite, etc.) and other crystal minerals (such as calcium carbonate, magnesium carbonate, calcium hydroxide, etc.), but also can further react chemically with clay minerals in the soil to generate similar hydrated gel minerals and other crystal minerals. Therefore, compared with cement materials, mixing the geotechnical solidifying agent in the present invention with the soil can generate more hydrated gel minerals and other crystal minerals. These hydrated gel minerals and crystal minerals grow in the soil. On the one hand, they connect the soil aggregates that have not participated in the chemical reaction, and on the other hand, they wrap the soil aggregates. With these two effects, the soil solidified by the solidifying agent has higher strength, impermeability, water stability and corrosion resistance, and can more effectively fix and wrap harmful substances in the solidified soil layer 3.

[0033] In some optional embodiments, in the solidifying agent powder, the cement is specifically P.O 42.5 cement, with a specific surface area ≥ 380 m 2 / kg and a loss on ignition ≤ 4.0%; the slag powder uses S95 grade blast furnace slag powder, with a specific surface area ≥ 400 m 2 / kg and a loss on ignition ≤ 3.0%; the fly ash is specifically grade II fly ash, with a specific surface area ≥ 300 m 2 / kg, fineness (residue on 45μm square-hole sieve) ≤ 20%, activity index ≥ 75%; the waste gypsum is specifically desulfurized gypsum or phosphogypsum, and the content of CaSO4·2H2O therein is greater than 85%; the modulus of water glass is between 2.0 and 3.5; the specific surface area of stone powder residue ≥ 350m 2 / kg; the slag is the waste residue discharged during the blast furnace smelting of pig iron, and the moisture content of the slag is controlled within 5%.

[0034] In some alternative embodiments, referring to Figure 3 As shown, the height of the solidified soil layer 3 is 3m to 6m. The sewage on which the solidified soil layer 3 acts includes the sewage participating in the chemical reaction and the remaining sewage fixed in the solidified soil layer 3. The present invention only solidifies the muck 7 in the surface area, and while achieving the effect of sewage closed solidification treatment, effectively isolates the solidified soil layer 3 and the clay layer 5 through the muck 7 in the lower area, avoiding the influence of the relevant components in the solidified soil layer 3 on the clay layer 5.

[0035] In some alternative embodiments, referring to Figure 1 As shown, before backfilling the muck 7 into the sewage pond 1, it further includes: making a closed curtain 2 along the circumferential direction of the sewage pond 1, and the bottom of the closed curtain 2 is located below the bottom of the sewage pond 1 and extends to the clay layer 5.

[0036] In the present invention, after the geotechnical curing agent is prepared into a slurry and stirred and solidified with the soil, the formed closed curtain 2 has good impermeability. The closed curtain 2 enters a certain depth into the impermeable clay layer 5, thereby completely isolating the sewage within the closed interval surrounded by the closed curtain 2, the solidified soil layer 3 and the clay layer 5, and avoiding the seepage and migration of harmful substances in the sewage pond 1 to the surrounding environment.

[0037] Specifically, referring to Figure 1 and Figure 4 As shown, in the present invention, the distance between the position of the closed curtain 2 and the edge of the sewage pond 1 is 1m to 2m. In the figure, h is the height of the closed curtain 2 entering the clay layer 5, and h is not less than 3m, that is, the bottom of the closed curtain 2 is located below the clay layer 5 and at least 3m lower than the surface of the clay layer 5. This is beneficial to fully improve the isolation performance of the closed interval and avoid the seepage and migration of harmful substances in the sewage pond 1 to the surrounding environment.

[0038] In some alternative embodiments, the closed curtain 2 is formed by mixing the geotechnical curing agent slurry with the soil and then stirring and solidifying. Specifically, referring to Figure 4As shown, the closed curtain 2 includes a plurality of solidifying agent piles, specifically formed by connecting a plurality of solidifying agent piles through the method of overlapping holes or partial overlapping method. Each solidifying agent pile can be made by a double-shaft mixing pile machine or a triple-shaft mixing pile machine, including: after determining the position of the closed curtain 2, conveying the geotechnical solidifying agent slurry to the drill pipe of the triple-shaft mixing pile machine through the grouting pump 6. A high-pressure rubber air pipe and a high-pressure rubber grouting pipe are respectively connected to the top of the drill pipe of the mixing pile machine. The grouting pipe is connected to the grouting pump 6 of the pulp preparation station to convey the geotechnical solidifying agent slurry. The air pipe is connected to the air compressor to convey compressed air. During the drilling process of the mixing drill, the drill bit sprays out the geotechnical solidifying agent slurry and compressed air. At the same time, a plurality of mixing blades are welded on the drill pipe, and the rotation of the drill pipe drives the mixing blades to rotate to fully mix the slurry and soil. The compressed air ejected from the drill bit also plays a role in tumbling and mixing, further fully mixing the geotechnical solidifying agent slurry and soil into a fluidized mixed slurry. After the solidifying agent slurry and soil are evenly mixed, the solidified slurry forms a solidifying agent pile after solidification. The solidifying agent piles with continuously overlapping holes become a continuous anti-seepage closed curtain 2.

[0039] Optionally, backfilling the muck 7 into the sewage pond 1 includes: the water content of the muck 7 does not exceed 25%. Specifically, the muck 7 can be sourced from the soil near the sewage pond 1, or the construction waste from the surrounding construction sites can be used as the muck 7. The muck 7 is crushed by a crusher bucket equipped with an excavator or a forklift to fully crush the lumps and large particles in the soil into small particles. After the crushed soil is concentrated and stacked and screened to remove particles with a particle size greater than 50 mm, it is then dried to make its water content not exceed 25% so as to absorb as much sewage as possible in the later stage.

[0040] In some alternative embodiments, the geotechnical solidifying agent slurry is formed by mixing solidifying agent powder and water, and in the geotechnical solidifying agent slurry, the mass ratio of the solidifying agent powder to water is 1:(1.5 to 3). In the solidified soil layer 3, the mass ratio of the muck 7 to the solidifying agent powder is 1:(0.2 to 0.25).

[0041] It should be noted that for the calculation of the filling volume in the sewage pond 1, the total mass of the muck 7 in the sewage pond 1 includes two parts: one part is the filling volume required for the upper solidified soil layer 3, and the other part is the filling volume required for the lower non-solidified soil layer 4. The filling volumes required for the solidified soil layer 3 and the non-solidified soil layer 4 can be calculated respectively with reference to the following formula (Ⅰ):

[0042]

[0043] In formula (Ⅰ), ρ is the density of the soil-water mixture formed after adding the muck into the sewage pond. The upper solidified soil layer is greatly affected by the walking disturbance of mechanical equipment such as excavators and dump trucks. Therefore, in a specific embodiment, the density of the soil-water mixture in the solidified soil layer can be taken as 1.4 t / m 3The lower unsolidified soil layer is less affected by the disturbance of mechanical equipment such as excavators and earthmoving vehicles due to its greater burial depth. Therefore, the density of the water-soil mixture in the unsolidified soil layer can be taken as 1.35t / m 3 G1 is the density of sewage, which can be 1t / m in a specific embodiment. 3 , G2 is the density of the slag, which can be 2.60t / m in a specific embodiment. 3 , ω is the moisture content of the slag, m1 is the total mass of the required slag, and m2 is the mass of the sewage in the sewage pond.

[0044] In addition, the mass of the curing agent powder required for making the closed curtain can be estimated by referring to the following method: first calculate the mass of the soil that reacts with the geotechnical curing agent slurry when making the closed curtain, which can be calculated by multiplying the total volume of the closed curtain opening area by the soil density. After calculating the mass of the soil that reacts with the geotechnical curing agent slurry, further convert the mass ratio of the required curing agent powder through the mass ratio.

[0045] The present invention is described in detail below through specific embodiments:

[0046] (I) Formula and dosage determination of rock and soil solidifier slurry

[0047] Test for determining the formula of geotechnical solidifying agent slurry:

[0048] The curing agent powder was prepared according to Table 1, and then the curing agent powder and water were mixed evenly at a ratio of 1:1.5 to obtain geotechnical curing agent slurry. Finally, the geotechnical curing agent slurry was added to the slag according to the mass ratio of slag to curing agent powder of 1:0.2, and the interface shear strength of the slag was tested at different times, namely 3d, 7d, 14d and 28d. The interface shear strength data are shown in Table 2:

[0049] Table 1 Formula of curing agent powder

[0050]

[0051] Table 2 Interface shear strength data of each formulation

[0052]

[0053]

[0054] According to Table 1 and Table 2, the interface shear strength of formulation No. 5 is the best, that is, the best curing agent powder formulation is 10 parts of cement, 30 parts of slag powder, 15 parts of fly ash, 25 parts of waste gypsum, 10 parts of water glass, 5 parts of stone powder slag, and 5 parts of slag.

[0055] Test for determining the dosage of geotechnical solidifying agent slurry:

[0056] Prepare the geotechnical solidifying agent slurry according to the above optimal powder formula of the solidifying agent (Formula 5). According to the mass ratio of muck to the powder of the solidifying agent being 1:(0.15 - 0.3), incorporate the geotechnical solidifying agent slurry formed by the above Formula 5 into the muck, and detect the interface shear strength of the muck at 3d, 7d, 14d, and 28d respectively. The interface shear strength data is shown in Table 3:

[0057] Table 3 Interface Shear Strength Data under Different Dosages of Geotechnical Solidifying Agent Slurry

[0058]

[0059] When the 28d strength requirement is 4.0 MPa, based on cost control and the need for strength surplus, the minimum dosage with an interface shear strength above 4.0*(1 + 20%) = 4.8 MPa should be selected. As can be seen from Table 3, in the embodiments of the present invention, the dosage range that meets the design strength requirements and has the lowest use cost is: the mass ratio of muck to the powder of the solidifying agent is 1:0.25.

[0060] (II) Fabrication of the Cut-off Curtain

[0061] First, mark the position 1 m away from the edge of the sewage pond to form a construction area for the cut-off curtain. Use a triple-axis mixing pile rig to drill downward in the marked construction area and inject the prepared geotechnical solidifying agent slurry in (I) at the optimal dosage. After the geotechnical solidifying agent slurry and the soil are evenly mixed and solidified, solidifying agent piles are formed. The solidifying agent piles with continuous socketed holes form a cut-off curtain. The bottom of the cut-off curtain enters the clay layer by a height of 4 m.

[0062] (III) Filling and Solidifying the Sewage Pond

[0063] Before formal filling, first evenly sprinkle soil materials along the periphery of the sewage pond. After the sprinkled soil materials are slightly consolidated, use the consolidated soil materials of the previous day as a construction platform for filling work the next day. During formal filling, take soil near the sewage pond or transport the engineering muck from a farther place to the vicinity. After screening and removing large particle sizes from the soil or engineering muck, stack them near the sewage pond for appropriate drying to make their water content not exceed 25% so as to absorb as much sewage as possible in the later stage. Then use an excavator or a forklift to evenly push the screened soil into the sewage pond until the sewage pond is completely filled. Specifically, a barge-mounted excavator can be used for backfilling and leveling the filling surface.

[0064] Then, use the double-wheel mixing head configured on the excavator to perform mixing and solidification treatment on the area 5m deep from the surface in the sewage pond. The two mixing heads are symmetrically distributed on both sides of the connecting rod and the nozzle. The geotechnical solidifying agent slurry enters the nozzle through the slurry spraying pipe by the background feeding system. Utilize the helically distributed cutter heads on the mixing head to three-dimensionally cut the soil body and rotate, and adopt the vertical up-and-down mixing and solidification method. The mixing equipment runs forward and gradually deepens the mixing and sprays the solidifying agent until it reaches the bottom of the set area, and then the mixing equipment runs backward and slowly lifts while mixing and spraying the solidifying agent. Among them, the rate of mixing lifting or lowering is controlled at 0.1 - 0.2m / s, and the slurry spraying rate of the solidifying agent is controlled at 100 - 200 Kg / min. At the same time, loft and divide the area to be solidified into blocks, and there should be a lap width of not less than 5cm between adjacent blocks to avoid missed mixing, and finally form a uniform solidified soil layer through solidification.

[0065] Although the present invention is disclosed as above, the protection scope of the present invention is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and these changes and modifications will all fall within the protection scope of the present invention.

Claims

1. A method for closed solidification treatment of sewage ponds, characterized in that, Including: Backfilling muck into the sewage pond; Injecting a geotechnical curing agent slurry into the muck in the surface area of the sewage pond and performing stirring and curing to form a cured soil layer; The geotechnical curing agent slurry includes a curing agent powder and water, and the curing agent powder includes components in the following mass fractions: cement: 10 to 40 parts, slag micro-powder: 30 to 60 parts, fly ash: 10 to 30 parts, waste gypsum: 5 to 25 parts, water glass: 5 to 15 parts, stone powder residue: 5 to 20 parts, slag: 5 to 15 parts.

2. The sewage pond enclosure and solidification treatment method according to claim 1, characterized in that, The height of the cured soil layer is 3m to 6m.

3. The sewage pond enclosure and solidification treatment method according to claim 1, characterized in that, Before backfilling muck into the sewage pond, it further includes: Fabricating a closed curtain along the circumferential direction of the sewage pond, the bottom of the closed curtain is located below the bottom of the sewage pond and extends to the clay layer.

4. The sewage pond enclosure and solidification treatment method according to claim 3, characterized in that, The height of the closed curtain entering the clay layer is not less than 3m.

5. The sewage pond enclosure and solidification treatment method according to claim 3, characterized in that, The closed curtain is formed by mixing the geotechnical curing agent slurry with soil and then performing stirring and curing.

6. The sewage pond enclosure and solidification treatment method according to claim 5, characterized in that, The position of the closed curtain is 1m to 2m away from the edge of the sewage pond.

7. The sewage pond enclosure and solidification treatment method according to claim 3, wherein The closed curtain includes a plurality of curing agent piles, and the plurality of curing agent piles are connected by the method of punching one hole or partial lapping.

8. The sewage pond enclosure and solidification treatment method according to claim 1, wherein, The backfilling of muck into the sewage pond includes: the water content of the muck does not exceed 25%.

9. The sewage pond enclosure and solidification treatment method according to claim 1, characterized in that In the geotechnical curing agent slurry, the mass ratio of the curing agent powder to water is 1:(1.5 to 3).

10. The sewage pond closed solidification treatment method according to claim 9, wherein, In the cured soil layer, the mass ratio of the muck to the geotechnical curing agent powder is 1:(0.2 to 0.25).

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