Environment-friendly backfill composite multifunctional layer construction process for comprehensive pipe gallery

Abstract

The invention discloses a construction technology for a green backfill composite multifunctional layer of a comprehensive pipe gallery, belongs to the technical field of comprehensive pipe gallery construction, and adopts various green backfill materials with different performances, porous medium materials, pervious concrete, foam concrete and flow state solidified soil to jointly construct a plurality of backfill layers with different functions. Each protective layer has the effects of adsorption pollution reduction, filtration interception and load reduction protection, and is combined with the water storage function of a sponge facility in a sponge city; while urban surface accumulated water and surface runoff pollution are reasonably treated, the water and soil load around the comprehensive pipe gallery is reduced, the anti-seepage performance of the pipe gallery is improved, and the environment-friendly backfill composite multifunctional layer construction technology gives consideration to urban water purification, water storage and pipe gallery structure protection; and the safety of long-term operation and maintenance of the comprehensive pipe gallery in a sponge city is facilitated.

Description

Technical Field

[0001] The invention belongs to the technical field of comprehensive pipe gallery construction, and specifically relates to a green backfill composite multifunctional layer construction process for a comprehensive pipe gallery. Background Art

[0002] Future urban development focuses on intensive, ecological, green, and resilient development, and the demand for integrated pipe corridors and sponge facilities will grow rapidly. As an important structure in the city's underground space, the underground pipe corridor is the main place for the centralized laying of large-scale pipelines. It integrates various engineering pipelines such as electricity, communications, gas, heating, water supply and drainage, and unifies the planning, design, construction and management of these pipelines. It is an important infrastructure and "lifeline" to ensure the operation of the city. During the project construction process, due to space constraints, the co-construction of integrated pipe corridors and sponge facilities will be inevitable, but the contradiction between the sponge facility's demand for the permeability of the backfill material and the anti-seepage of the integrated pipe corridor is a major problem in the co-construction of the two.

[0003] At present, sponge facilities mainly use permeable materials such as concrete to "seep", "store" and "purify" runoff rainwater; however, when building a comprehensive pipe corridor in a sponge city, while achieving the purpose of water storage and water storage, ordinary pipe backfilling methods and backfilling materials are prone to cause water seepage or even leakage in the pipe corridor; and the water storage of the upper sponge facilities is prone to cause additional water pressure on the pipe corridor structure, resulting in unreasonable structural design. The fertilizer troughs on both sides of the comprehensive pipe corridor are mainly backfilled with sand. Due to the good structural permeability of the upper sponge facility layer, surface water infiltrates into the surrounding area of ​​the comprehensive pipe corridor through the upper sponge facility layer and the sand backfill layer, causing groundwater to gather around the pipe corridor. Under the action of water and soil pressure, the risk of water seepage and damage to the pipe corridor structure of the comprehensive pipe corridor is increased. At the same time, when the comprehensive pipe corridor is backfilled, due to the small width of the fertilizer troughs on both sides, the density of the backfilled sand is difficult to meet the requirements, threatening the long-term operation and maintenance safety of various municipal pipelines inside. On the other hand, in areas with poor geological conditions, a large amount of sand and gravel soil needs to be purchased from outside, which greatly increases the cost of pipe corridor construction. However, the large amount of solid waste generated by industry and construction in the construction area often has no disposal method, which cannot meet the needs of green and resilient development of the city. Summary of the invention

[0004] The purpose of the present invention is to solve the problem that the existing green backfill composite multifunctional layer of the comprehensive pipe gallery has a high water permeability, a high risk of pipe gallery structure damage, and a high cost of pipe gallery construction, which cannot meet the needs of urban green development. A construction process of a green backfill composite multifunctional layer of a comprehensive pipe gallery is proposed, and multiple backfill layers with different functions are jointly constructed by using a variety of green backfill materials, porous medium materials, permeable concrete, foamed concrete, and fluidized solidified soil with different properties. Each protective layer plays the role of adsorption and pollution reduction, filtration and interception, and load reduction and protection, while combining the water storage function of the sponge facilities in the sponge city; while reasonably dealing with urban surface water accumulation and surface runoff pollution, it plays a role in reducing the water and soil load around the comprehensive pipe gallery and increasing the anti-seepage performance of the pipe gallery. It is a green backfill composite multifunctional layer construction process that takes into account urban water purification, water storage, and pipe gallery structure protection, and is also conducive to the safety of long-term operation and maintenance of the comprehensive pipe gallery in the sponge city.

[0005] In order to solve the above technical problems, the present invention provides a construction process of a green backfill composite multifunctional layer of an integrated pipe gallery, comprising: a construction process of a green backfill composite multifunctional layer of an integrated pipe gallery, characterized in that it comprises the following steps:

[0006] S1. Prepare relevant equipment, level the excavated ground and backfill materials in advance, excavate the foundation pit of the comprehensive pipeline corridor and set the lowest foundation according to the design elevation requirements;

[0007] S2. Based on the strength design requirements, a cushion layer is formed by pouring fluidized solidified soil above the foundation;

[0008] S3. The integrated pipe gallery is constructed by cast-in-place or prefabrication above the cushion layer. After the concrete of the integrated pipe gallery reaches the designed strength, the fluidized solidified soil is poured in the fertilizer troughs of the foundation pit on both sides of the integrated pipe gallery to form a protective layer around the pipe gallery, and the top of the integrated pipe gallery is poured until it reaches the designed height;

[0009] S4. After the protective layer around the pipe gallery reaches the designed strength, the intermediate load-reducing layer is poured above the protective layer around the pipe gallery using geopolymer foam concrete until it reaches the designed height;

[0010] S5. After the middle load-reducing layer is backfilled, geopolymer permeable concrete mixed with porous medium materials is used as the sponge facility layer to backfill above the middle load-reducing layer to the designed height.

[0011] Preferably, the fluidized solidified soil comprises construction waste, an alkali activator (modulus of 1.2) formed by a mixture of NaOH and water glass, and a geopolymer cementitious material formed by a mixture of fly ash and blast furnace slag powder.

[0012] As a preferred method, the fluidized solidified soil is prepared by solidifying construction waste soil with geopolymer cementitious materials, wherein the fly ash content in the geopolymer cementitious materials is about 52%, the mineral powder content is about 34%, and the composite alkali activator content is about 14%. In addition, the construction waste soil requires a sand-to-cement ratio of 1.5, a waste soil particle size of ≤4.75 mm, and a water-to-cement ratio of 0.78.

[0013] Preferably, the geopolymer foam concrete is prepared from materials such as building debris, geopolymer cementitious materials, and prefabricated foams. Among them, the geopolymer cementitious materials include low-calcium fly ash and S95 granulated blast furnace slag powder. The alkali activator adopts a mixed solution of NaOH and water glass, and its modulus is 1.2. K12 and xanthan gum are mixed and dissolved in water to form a composite foaming agent solution, and the prefabricated foam is made by air compression.

[0014] Preferably, the geopolymer permeable concrete is prepared by geopolymer cementitious materials and recycled aggregates from construction waste. The raw materials of the geopolymer cementitious materials include low-calcium fly ash, S95 granulated blast furnace slag powder, and a density of 1.8 g / cm 3 The densified silica fume and the alkali activator are mixed solutions of water glass solution and solid NaOH (modulus 1.2). In addition, the particle size gradation of recycled coarse aggregate is 4.75-9.5 mm, and the water-binder ratio of permeable concrete is 0.3.

[0015] Preferably, the porous medium material is made of pyrolyzed wastewater treatment plant residual sludge, steel slag, and coal-based activated carbon.

[0016] Beneficial effects of the present invention:

[0017] 1. This solution uses a variety of green backfill materials, porous media materials, permeable concrete, foamed concrete, and fluidized solidified soil with different properties to jointly construct multiple backfill layers with different functions. Each protective layer plays the role of adsorption and pollution reduction, filtration and interception, and load reduction and protection. While taking into account the purpose of water storage, it plays the role of load reduction, support protection, and water isolation and anti-seepage for the pipe gallery below, which is suitable for implementation in sponge cities. The load reduction layer in the present invention not only reduces the load on the structure below, but also has the function of purification and filtration; and the load reduction layer can be connected to groundwater to achieve the purpose of water discharge and drainage, greatly reducing the possibility of water seepage to the lower layer; in terms of improving the stress of the pipe gallery below, the present invention is provided with a protective layer, and a controllable low-strength self-leveling material is used for backfilling, so as to form a dense and strong supporting protective layer to meet the bearing capacity requirements of the building specifications.

[0018] 2. This plan uses permeable concrete mixed with porous media materials to backfill the top sponge facility layer, which serves as the ground roadbed. It also absorbs, filters and purifies the surface runoff water that directly seeps down, avoiding water accumulation on the ground after rain in the city while purifying and storing water. It reduces the possibility of urban waterlogging and reduces the burden on the urban drainage system; it also replenishes groundwater, which can provide irrigation water to the city during droughts and realize the reuse of water resources.

[0019] 3. This scheme adopts foam concrete mixed with porous medium material backfill through the middle load-reducing layer. The characteristics of light weight and self-leveling greatly reduce the load on the pipe gallery below. In addition, due to the special properties of the backfill material, the seepage water can be further filtered and treated, and impurities and harmful substances in the water can be adsorbed and purified. It also involves the strengthening effect of geopolymers in permeable concrete on porous medium materials. At the same time, the load-reducing layer is connected to the groundwater during design, and the secondary filtered seepage water can be directly discharged into the groundwater through the load-reducing layer, further reducing the risk of water seepage in the pipe gallery.

[0020] 4. This scheme adopts fluidized solidified soil backfill in the protective layer around the pipe gallery. It has the characteristics of high fluidity, high deformation modulus and self-compactness. It can effectively bear the load generated by the upper backfill material, while isolating the groundwater in the load-reducing layer, reducing the water and soil pressure on the integrated pipe gallery structure, and playing a supporting and waterproofing role for the pipe gallery structure below.

[0021] 5. This scheme allows the use of the same fluidized solidified soil backfill as the protective layer in the cushion layer under the integrated pipeline corridor. Its high fluidity, high deformation modulus, and self-compacting properties ensure the stiffness and anti-seepage requirements of the cushion layer, while facilitating construction and leveling. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Other features, objects and advantages of the present invention will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings. The drawings are only for the purpose of illustrating preferred embodiments and are not to be considered as limiting the present invention. Also, the same reference symbols are used throughout the drawings to represent the same parts.

[0023] Figure 1 This is a schematic diagram of the backfill structure of the integrated pipe gallery according to an embodiment of the present invention;

[0024] Figure 2 The present invention is a flow chart of the preparation process of geopolymer permeable concrete;

[0025] Figure 3 The present invention is a flow chart of the preparation process of the geopolymer foam concrete. DETAILED DESCRIPTION

[0026] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific implementation method described herein is only an optimal embodiment of the present invention, which is only used to explain the present invention and does not limit the scope of protection of the present invention. All other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0027] Example 1: Figure 1 As shown, a green backfill composite multifunctional layer construction process for a comprehensive pipe gallery includes:

[0028] S1. Prepare relevant equipment, level the excavated ground and backfill materials in advance, excavate the foundation pit of the comprehensive pipeline corridor and set the lowest foundation 1 according to the design elevation requirements;

[0029] S2. Based on the strength design requirements, a cushion layer 2 is formed by pouring fluidized solidified soil on the foundation 1;

[0030] S3. The integrated pipe gallery 4 is constructed by cast-in-place or prefabrication above the cushion layer 2. After the concrete of the integrated pipe gallery 4 reaches the designed strength, fluidized solidified soil is poured in the fertilizer troughs of the foundation pits on both sides of the integrated pipe gallery 4 to form a protective layer 3 around the pipe gallery and poured on the top of the integrated pipe gallery 4 until the designed height is reached;

[0031] S4, after the protective layer 3 around the pipe gallery reaches the design strength, the intermediate load-reducing layer 5 is poured above the protective layer 3 around the pipe gallery by using geopolymer foam concrete until the design height is reached;

[0032] S5. After the middle load-reducing layer 5 is backfilled, a geopolymer permeable concrete mixed with porous medium material is used as a sponge facility layer 6 to backfill above the middle load-reducing layer to the designed height.

[0033] Specifically, the fluidized solidified soil includes: construction waste soil; an alkali activator (modulus is 1.2) formed by mixing NaOH and water glass; and a geopolymer cementitious material formed by mixing fly ash and blast furnace slag powder.

[0034] The surrounding protective layer and cushion layer are fluidized solidified soil, which is made of construction waste soil, geopolymer cementitious materials and alkali activator to form geopolymer fluidized solidified soil with high fluidity and self-compacting properties. Among them, the alkali activator is a mixed solution of NaOH and water glass (modulus is 1.2); the cementitious materials include fly ash and blast furnace slag powder.

[0035] Fluidized solidified soil has the following characteristics:

[0036] ① Fluidity. This material has the property of self-leveling. It can be backfilled into the corresponding engineering parts like concrete pouring without compaction. It can be well applied to the backfilling of pipe trenches, foundation trenches, inspection well peripheries, abutment backs, and other parts where the working surface is insufficient and difficult to construct and roll.

[0037] ② Non-sinking. Compared with general backfill materials, this material has better volume stability. Due to its good flowability, it can be self-compacted under its own weight. That is to say, after hardening, the material has a uniform texture and will not sink, which greatly improves the durability of the filling structure.

[0038] ③ Self-compacting property. Compared with general filling materials, fluidized solidified soil can flow freely and compact due to its good fluidity, which can improve the surface quality of concrete and does not require manual vibration, thus improving production efficiency and shortening working time.

[0039] The protective layer around the tunnel is backfilled with fluidized solidified soil, which has the characteristics of high fluidity, high deformation modulus and self-compactness. It can effectively bear the load generated by the upper backfill material, while isolating the groundwater in the load-reducing layer, reducing the water and soil pressure on the integrated tunnel structure, and playing a supporting and waterproofing role for the tunnel structure below.

[0040] Specifically, Table 1 is the design mix ratio table of geopolymer fluidized soil, and Table 2 is the working performance and mechanical properties table of geopolymer fluidized soil. It can be seen from the table that the optimal formula of fluidized soil is the test group numbered WS3, and the mix ratio of fluidized soil is geopolymer cementitious material, in which the fly ash content is about 52%, the mineral powder content is about 34%, and the composite alkali activator content is about 14%. In addition, the sand-cement ratio is required to be 1.5, the slag particle size is ≤4.75mm, and the water-cement ratio is 0.78.

[0041] Table 1 Design mix ratio of geopolymer fluidized soil

[0042]

[0043] Note: Sand-cement ratio refers to the ratio of slag to geopolymer cementitious material.

[0044] Table 2 Working performance and mechanical properties of geopolymer fluidized soil

[0045]

[0046]

[0047] Therefore, it can be seen from the above table that the optimal formula of geopolymer fluidized soil is the test group numbered WS3, which can maintain a high slag content while maintaining high early and late compressive strengths.

[0048] The middle load-reducing layer is foamed concrete, which is made of: construction waste soil mixed with geopolymer cementitious materials, alkali activator, and prefabricated foam. Among them, the cementitious materials include national grade I low-calcium fly ash and S95 granulated blast furnace slag powder. The composite alkali activator is a mixed solution of NaOH and water glass (modulus 1.2). The prefabricated foam is made of K12 and xanthan gum mixed evenly and dissolved in water to form a composite foaming agent solution, and the prefabricated foam is made by air compression.

[0049] When preparing geopolymer foam concrete, first add fly ash and mineral powder into the mixer and mix them evenly to obtain fly ash mineral powder composite powder, then add the prepared composite alkali activator and water into the mixer and mix evenly to obtain geopolymer slurry, finally add prefabricated foam and mix to obtain geopolymer foam concrete. The functions of geopolymer foam concrete include two parts: first, it intercepts and adsorbs pollutants by adding adsorbents such as activated carbon, and promotes the infiltration of upper water; second, it has a load-reducing effect, which reduces its own load by controlling its own structure, so as to achieve the function of load-reducing backfilling. The preparation process of geopolymer foam concrete is as follows: Figure 3 As shown. When preparing geopolymer slurry, the water-solid ratio of the geopolymer slurry used in geopolymer foam concrete is 0.35. Its total solid content includes the mass of fly ash, the mass of mineral powder and the solid phase mass of composite alkali activator. The total solid content is set at 350g, of which the fly ash content is about 51.6% (180.6g), the mineral powder content is about 34.4% (120.4g), and the composite alkali activator parameter is about 14% (solid phase content is 49g). As shown in Table 3, it is the mix design of geopolymer foam concrete; Table 4 is the macroscopic properties of geopolymer foam concrete.

[0050] Table 3 Geopolymer foam concrete mix design

[0051]

[0052] Table 4 Macro properties of geopolymer foam concrete

[0053]

[0054] Therefore, the optimal formula of geopolymer foam concrete is the experimental group numbered FA4, which has higher compressive strength and softening coefficient while maintaining a lower dry density.

[0055] Specifically, the geopolymer foam concrete is made by mixing construction waste, geopolymer gelling material, alkali activator and prefabricated foam. Among them, the geopolymer gelling material includes low-calcium fly ash and S95 granulated blast furnace slag powder. The alkali activator adopts a mixed solution of NaOH and water glass, and its modulus is 1.2. K12 and xanthan gum are mixed and dissolved in water to form a composite foaming agent solution, and the prefabricated foam is made by air compression.

[0056] Specifically, geopolymer permeable concrete uses a combination of recycled aggregate from construction waste and geopolymer cementitious materials. The cementitious raw materials that make up the geopolymer include: low-calcium fly ash, S95 granulated blast furnace slag powder with irregular rhombus polyhedron micromorphology, and densified silica fume. Its alkali activator is a mixed solution of water glass solution and solid NaOH (modulus 1.2). In addition, the particle size gradation of the recycled coarse aggregate is 4.75-9.5mm, and the water-cement ratio of the permeable concrete is 0.3.

[0057] Specifically, the porous medium material includes residual sludge from a sewage treatment plant after pyrolysis by a pyrolysis method, steel slag, and coal-based activated carbon.

[0058] This plan uses a permeable concrete mixed with porous media materials to backfill the top sponge facility layer, which serves as the ground roadbed. It also absorbs, filters and purifies the surface runoff water that directly seeps down, avoiding water accumulation on the ground after rain in the city while purifying and storing water. It reduces the possibility of urban waterlogging and reduces the burden on the urban drainage system; it also replenishes groundwater, which can provide irrigation water to the city during droughts and realize the reuse of water resources.

[0059] The top sponge facility layer is permeable concrete, which uses a combination of recycled aggregate from construction waste and geopolymer cementitious materials. The cementitious raw materials that make up the geopolymer include: National Grade I low-calcium fly ash (FA); S95 granulated blast furnace slag powder (GBFS) with irregular rhombus polyhedron micromorphology; and densified silica fume. The alkali activator is a mixed solution of water glass solution and solid NaOH, and its modulus is 1.2. The recycled coarse aggregate has a particle size gradation of 4.75 to 9.5 mm and is screened, rinsed, and dried before the test. The water-cement ratio of permeable concrete is 0.3. The preparation process is as follows: Figure 2 The geopolymer permeable concrete was tested through Tables 5 and 6.

[0060] Table 5 Detailed mix proportion of geopolymer permeable concrete

[0061]

[0062]

[0063] Table 6 Experimental results of geopolymer permeable concrete

[0064]

[0065] Therefore, combined with Table 5 and Table 6, the optimal formula of geopolymer permeable concrete is the No. 8 test ratio, at which the water-cement ratio is moderate, the amount of alkali activator is small, and the various indicators of the performance of this ratio can reach a relatively balanced excellent level. Compared with cement permeable concrete, geopolymer permeable concrete has the characteristics of early strength and high strength, and also has better mechanical properties and chemical corrosion resistance. In addition, the use of geopolymer permeable concrete will absorb a large amount of industrial solid waste, which is of practical significance for energy conservation and environmental protection.

[0066] Porous media materials: The porous media materials of the present invention utilize a variety of solid wastes as resources, mainly including residual sludge from sewage treatment plants after pyrolysis, steel slag, and coal-based activated carbon. The top layer of traditional sponge facilities is a mixture of 30-60% sand, 20-30% soil, and 20-40% organic matter by volume. It has a significant effect on removing particulate matter in surface runoff, but the removal effect on soluble organic pollutants such as nitrogen and phosphorus fluctuates greatly. The porous media materials (residual sludge after pyrolysis, steel slag, and coal-based activated carbon) added by the present invention can improve the top layer of existing traditional sponge facilities, allowing it to exert a better nitrogen and phosphorus removal effect.

[0067] Characteristics of porous media materials: Analyze the best formula of pyrolysis sludge, steel slag, and coal-based activated carbon in porous media materials, and analyze the effects of each formula on the ammonia nitrogen (NH 4+ -N) and phosphate (PO4 3- ) has an adsorption and purification effect. Pyrolysis sludge has a very developed microporous structure, and the residual sludge from the sewage treatment plant itself has a high content of Al or Fe cations. Steel slag promotes the precipitation of phosphorus pollutants, especially through chelation with various minerals and organic compounds to form various mineral organic complexes or chelates. Coal-based activated carbon promotes the adsorption of nitrogen and phosphorus pollutants with its ultra-high specific surface area.

[0068] The porous medium material is prepared by pyrolyzing the excess sludge from the sewage treatment plant, specifically, the excess sludge from the sewage treatment plant is first naturally air-dried, and then pyrolyzed in a muffle furnace set at 600°C for 3 hours. The pyrolyzed sludge, steel slag, and coal-based activated carbon are all passed through a 0.15mm sieve to prepare the porous medium material.

[0069] The packed column experiment was conducted according to the parameters in Tables 7 and 8. The column was made of UPVC material, and the inner wall was roughened to prevent short-circuiting. The column was 30 cm high, 4 cm in inner diameter, and the packing weight was about 200 g (height 20-25 cm). The packing was based on the above-mentioned "combination of recycled aggregates from construction waste and geopolymers", and 3% of organic compost was added as an additional carbon source, and then mixed with porous media materials. The formulas of the four groups of porous media material experiments are shown in the following table.

[0070] Table 7 Detailed proportion of porous media materials

[0071] experiment Pyrolysis sludge Steel slag Coal-based activated carbon 1 3％ 3％ 3％ 2 0％ 3％ 3％ 3 3％ 0％ 3％ 4 3％ 3％ 0％

[0072] The artificial simulated surface runoff rainwater is: glucose represents the pollutant index COD (300 mg / L), ammonium chloride represents the pollutant index NH 4+ -N (4mg / L), potassium dihydrogen phosphate represents the pollutant index total phosphorus (TP) (1.2mg / L). The design is to inlet water for 60min every 24h, with an inlet flow rate of 5mL / min. Deionized water is injected for 5 days using a peristaltic pump, and then artificial simulated rainwater is injected for several days (until the outlet water concentration is greater than the inlet water concentration). During the experiment, water samples are collected every 5 minutes until the experimental column no longer discharges water.

[0073] The effects of four groups of experiments on porous media materials in treating artificially simulated surface runoff rainwater are shown in Table 8 below.

[0074] Table 8 Effect of treating artificial simulated surface runoff rainwater

[0075] Experimental Group Average removal rate 1 84％±10％ 2 32％±10％ 3 25％±5％ 4 28％±15％

[0076] Therefore, combining Table 7 and Table 8, the optimal porous media material formula comes from Experimental Group 1, that is, pyrolysis sludge, steel slag, and coal-based activated carbon each account for 3%.

[0077] Purification and removal mechanism of nitrogen and phosphorus pollutants in rainwater surface runoff by porous media materials:

[0078] ①NH 4+ -N pollutants

[0079] NH in stormwater runoff 4+ After entering the top sponge facility layer with rainwater runoff, -N is first adsorbed by negatively charged pyrolysis sludge and coal-based activated carbon filler particles, and NH 4+ The purification and removal effect of -N depends on the cation exchange capacity of these fillers and the electrostatic attraction of oxygen-containing functional groups on the surface of the material.

[0080] ②PO4 3－ Pollutants

[0081] PO4 in Stormwater Runoff3－ The purification and removal of pollutants is not only the role of porous media materials, but also involves the strengthening effect of geopolymers in permeable concrete on porous media materials.

[0082] First, PO4 in stormwater runoff 3－ The removal of divalent or trivalent metal ions (e.g., Ca from low-calcium fly ash in geopolymers) is accomplished by chemical precipitation and adsorption of geopolymers. 2+ and Mg 2+ , Al in blast furnace slag powder 3+ , Fe 3+ ), can be used with PO4 3－ Combined to form stable compounds such as magnesium phosphate crystals and hydroxyapatite, which are then retained in the porous medium filler.

[0083] Secondly, especially Al in geopolymer blast furnace slag powder 3+ and Fe 3+ , as well as the alkaline activators water glass solution and solid NaOH, all enhanced the effect of Al or Fe cations in the pyrolyzed sludge. The adsorption and purification process of phosphorus in rainwater runoff is divided into two types of reactions: surface site reaction (outer sphere complex reaction), which is characterized by fast reaction rate and high reversibility; and reaction of phosphorus with metal oxide mineral structures (inner sphere complex reaction), which is characterized by moderate reaction rate and irreversible reaction.

[0084] (a) Cationic Al in geopolymer blast furnace slag powder 3+ and Fe 3+ By forming an inner sphere complex, it reacts with PO4 3－ The strong binding of anions can efficiently and stably remove phosphorus-containing pollutants.

[0085] (b) The alkaline activator water glass solution and solid NaOH of the geopolymer can provide a good alkaline pH environment, thereby selectively carrying out the inner sphere complex reaction (rather than the outer sphere complex reaction) to make PO4 3－ Pollutants can be removed stably.

[0086] The above specific embodiments are preferred embodiments of the present invention, and are not intended to limit the specific implementation scope of the present invention. The scope of the present invention includes but is not limited to the present specific embodiments. All equivalent changes made in accordance with the shape, structure, and method of the present invention are within the protection scope of the present invention.

Claims

1. A green backfill composite multifunctional layer construction process for a comprehensive pipe gallery, characterized in that: include: S1. Prepare relevant equipment, level the excavated ground and backfill materials in advance, excavate the foundation pit of the integrated pipeline corridor and set the lowest foundation according to the design elevation requirements (1); S2. Based on the strength design requirements, a cushion layer (2) is formed by pouring fluidized solidified soil on top of the foundation (1); S3. The integrated pipe gallery (4) is constructed on the cushion layer (2) by cast-in-place or prefabrication. After the concrete of the integrated pipe gallery (4) reaches the designed strength, fluidized solidified soil is poured in the fertilizer troughs of the foundation pit on both sides of the integrated pipe gallery (4) to form a protective layer (3) around the pipe gallery, and poured on the top of the integrated pipe gallery (4) until the designed height is reached; S4, after the protective layer (3) around the pipe gallery reaches the designed strength, the intermediate load-reducing layer (5) is poured above the protective layer (3) around the pipe gallery using geopolymer foam concrete until the designed height is reached; S5. After the middle load-reducing layer (5) is backfilled, a geopolymer permeable concrete mixed with a porous medium material is used as a sponge facility layer (6) to backfill above the middle load-reducing layer (5) to a designed height.

2. The green backfill composite multifunctional layer construction process of the integrated pipe gallery according to claim 1 is characterized by: The fluidized solidified soil includes construction waste; Alkali activator with modulus of 1.2; geopolymer cementitious material mixed with fly ash and blast furnace slag powder.

3. The green backfill composite multifunctional layer construction process of the integrated pipe gallery according to claim 2 is characterized by: Fluidized solidified soil is prepared by solidifying construction waste with geopolymer cementitious materials, in which the mixing ratio of geopolymer cementitious materials is 52% fly ash, 34% mineral powder and 14% composite alkali activator; the sand-to-cement ratio of the construction waste is 1.5, the particle size of the waste is ≦4.75mm and the water-to-cement ratio is 0.

78.

4. The green backfill composite multifunctional layer construction process of the integrated pipe gallery according to claim 1 is characterized by: The geopolymer foam concrete is prepared by mixing construction waste, geopolymer gelling material, alkali activator and prefabricated foam; wherein the geopolymer gelling material comprises low-calcium fly ash; S95 granulated blast furnace slag powder; an alkali activator with a modulus of 1.2 made from a mixed solution of NaOH and water glass; a composite foaming agent solution is prepared by mixing K12 and xanthan gum evenly and dissolving them in water, and the prefabricated foam is prepared by air compression.

5. The green backfill composite multifunctional layer construction process of the integrated pipe gallery according to claim 1 is characterized by: The geopolymer permeable concrete is prepared by using recycled aggregate from construction waste and geopolymer cementitious materials; the raw materials of the geopolymer cementitious materials include low-calcium fly ash with a density of 2.9 g / cm 3 , S95 granulated blast furnace slag powder, density is 1.8g / cm 3 Densified silica fume; alkali activator with a modulus of 1.2 made from a mixed solution of NaOH and water glass; the particle size gradation of recycled coarse aggregate is 4.75-9.5mm, and the water-cement ratio of permeable concrete is 0.

3.

6. The green backfill composite multifunctional layer construction process of the integrated pipe gallery according to claim 5 is characterized by: The porous medium material includes residual sludge from a sewage treatment plant, steel slag and coal-based activated carbon after pyrolysis by a pyrolysis method, wherein the pyrolysis sludge, steel slag and coal-based activated carbon each account for 3%.

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