CN116023080A - Preparation process of flowing backfill based on shield waste slurry - Google Patents
Preparation process of flowing backfill based on shield waste slurry Download PDFInfo
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- 239000002002 slurry Substances 0.000 title claims abstract description 129
- 239000002699 waste material Substances 0.000 title claims abstract description 75
- 238000002360 preparation method Methods 0.000 title claims abstract description 30
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 82
- 239000000203 mixture Substances 0.000 claims abstract description 42
- 238000002156 mixing Methods 0.000 claims abstract description 34
- 239000003638 chemical reducing agent Substances 0.000 claims abstract description 31
- 238000000034 method Methods 0.000 claims abstract description 27
- 239000000701 coagulant Substances 0.000 claims abstract description 24
- 238000005189 flocculation Methods 0.000 claims abstract description 22
- 230000016615 flocculation Effects 0.000 claims abstract description 22
- 239000000463 material Substances 0.000 claims abstract description 22
- 238000003756 stirring Methods 0.000 claims abstract description 22
- 239000004568 cement Substances 0.000 claims abstract description 21
- 239000010881 fly ash Substances 0.000 claims abstract description 21
- 230000003750 conditioning effect Effects 0.000 claims abstract description 17
- 238000000926 separation method Methods 0.000 claims abstract description 16
- 239000002245 particle Substances 0.000 claims description 29
- 239000008394 flocculating agent Substances 0.000 claims description 23
- 238000012216 screening Methods 0.000 claims description 16
- 230000009969 flowable effect Effects 0.000 claims description 15
- 239000004744 fabric Substances 0.000 claims description 10
- 229920002401 polyacrylamide Polymers 0.000 claims description 7
- 125000000129 anionic group Chemical group 0.000 claims description 6
- 238000004519 manufacturing process Methods 0.000 claims description 6
- 239000004570 mortar (masonry) Substances 0.000 claims description 5
- CBOCVOKPQGJKKJ-UHFFFAOYSA-L Calcium formate Chemical compound [Ca+2].[O-]C=O.[O-]C=O CBOCVOKPQGJKKJ-UHFFFAOYSA-L 0.000 claims description 3
- 229910019142 PO4 Inorganic materials 0.000 claims description 3
- 239000004115 Sodium Silicate Substances 0.000 claims description 3
- 229940044172 calcium formate Drugs 0.000 claims description 3
- 235000019255 calcium formate Nutrition 0.000 claims description 3
- 239000004281 calcium formate Substances 0.000 claims description 3
- 239000010452 phosphate Substances 0.000 claims description 3
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 claims description 3
- 229920005646 polycarboxylate Polymers 0.000 claims description 3
- NTHWMYGWWRZVTN-UHFFFAOYSA-N sodium silicate Chemical compound [Na+].[Na+].[O-][Si]([O-])=O NTHWMYGWWRZVTN-UHFFFAOYSA-N 0.000 claims description 3
- 229910052911 sodium silicate Inorganic materials 0.000 claims description 3
- 230000001143 conditioned effect Effects 0.000 claims description 2
- 238000010276 construction Methods 0.000 abstract description 14
- 230000018044 dehydration Effects 0.000 description 7
- 238000006297 dehydration reaction Methods 0.000 description 7
- 230000000052 comparative effect Effects 0.000 description 6
- 230000003311 flocculating effect Effects 0.000 description 6
- 239000012528 membrane Substances 0.000 description 6
- 239000000440 bentonite Substances 0.000 description 4
- 229910000278 bentonite Inorganic materials 0.000 description 4
- SVPXDRXYRYOSEX-UHFFFAOYSA-N bentoquatam Chemical compound O.O=[Si]=O.O=[Al]O[Al]=O SVPXDRXYRYOSEX-UHFFFAOYSA-N 0.000 description 4
- 239000004927 clay Substances 0.000 description 4
- 229910052570 clay Inorganic materials 0.000 description 4
- 239000002689 soil Substances 0.000 description 4
- 238000011282 treatment Methods 0.000 description 4
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 238000003825 pressing Methods 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- 238000004064 recycling Methods 0.000 description 3
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 2
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- 230000005641 tunneling Effects 0.000 description 2
- 229920002134 Carboxymethyl cellulose Polymers 0.000 description 1
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- 239000001768 carboxy methyl cellulose Substances 0.000 description 1
- 235000010948 carboxy methyl cellulose Nutrition 0.000 description 1
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- 239000003153 chemical reaction reagent Substances 0.000 description 1
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- 229910000029 sodium carbonate Inorganic materials 0.000 description 1
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/91—Use of waste materials as fillers for mortars or concrete
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- Treatment Of Sludge (AREA)
Abstract
The invention discloses a preparation process of a flowing backfill based on shield waste mud, which comprises the following three steps: step 1: multistage separation is carried out on the waste slurry, and aggregates in the waste slurry are screened to obtain coarse aggregates, fine aggregates and uniform slurry obtained by mixing; step 2: the slurry is flocculated and dehydrated, the uniform slurry after multistage separation is treated by adopting a flocculation conditioning and vacuum preloading method to form a dehydrated mud cake, and discharged water forms slurry tail water; step 3: preparing flowing backfill, namely mixing coarse aggregate and fine aggregate in the step 1 with dehydrated mud cakes in the step 2 to form an aggregate mixture, and mixing slurry tail water generated in the step 2 with cement, fly ash, a water reducing agent and a coagulant to form a gel mixture, and stirring the aggregate mixture and the gel mixture to prepare the flowing backfill. The invention realizes the resource utilization of the shield waste slurry and solves the problem of backfill material preparation in engineering construction.
Description
Technical Field
The invention relates to the technical field of waste mud resource utilization and backfill preparation. More particularly, the invention relates to a process for preparing a flowing backfill based on shield waste mud.
Background
Along with the rapid development of the economy in China, the construction scale of tunnel engineering is continuously increased, and the output of the shield waste mud is increased year by year. In slurry balance shield construction operation, slurry is an indispensable substance for ensuring normal operation of the shield, and can play roles in balancing stratum pressure, protecting well walls, cleaning well bottoms, transmitting power and the like. At present, mud participates in the cutting of soil and bedrock in stratum in the construction process, rock scraps and soil are mixed, a complex mixed system is formed, and waste mud which cannot be reused is inevitably generated. At present, the shield mud generally adopts bentonite mud, and mainly comprises water, bentonite particles, clay particles, polyacrylamide, carboxymethyl cellulose and other additives. The waste mud has the following characteristics: (1) The addition of the additive results in higher pH of the slurry, which is generally alkaline; (2) The water content is higher, generally 60-90%, the consistency is higher, and natural sedimentation is difficult; (3) The clay mineral and other fine grains have large proportion and contain coarse grain gravel in certain proportion. At present, the treatment mode of the shield waste slurry is mainly a solid-liquid separation treatment method, colloid suspended matters are destabilized and settled by adding a flocculating agent, then solid-liquid separation is carried out by adopting a mechanical filter pressing mode, and finally the produced mud cake is transported to a landfill site for landfill. The method leads to that mud cakes serving as soil resources are not effectively utilized, and more land is occupied when the mud cakes are transported to a landfill, so that resource waste is caused.
The flowing backfill is a novel backfill material with fluidity and pouring construction, and is formed by adding a curing material, and the novel backfill material is generally composed of cement, fly ash, coarse aggregate, fine aggregate and water, has the characteristics of self-leveling and self-compaction, and is mainly used for engineering such as pipe ditch backfill, abutment back backfill and the like. The shield waste slurry contains rich aggregate, and the slurry is prepared into flowing backfill for backfill engineering through a series of treatments, so that the method is a solution for simultaneously solving three problems of waste slurry treatment, filling material purchase and backfill construction.
Disclosure of Invention
The invention aims to provide a preparation process of a flowing backfill based on shield waste slurry, which realizes the recycling of the shield waste slurry and solves the problem of backfill material preparation in engineering construction.
To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, there is provided a process for preparing a flowable backfill material based on shield-discarded slurry, comprising the steps of:
step 1: multistage separation is carried out on the waste slurry, and aggregates in the waste slurry are screened to obtain coarse aggregates, fine aggregates and uniform slurry obtained by mixing;
step 2: the slurry is flocculated and dehydrated, the uniform slurry after multistage separation is treated by adopting a flocculation conditioning and vacuum preloading method to form a dehydrated mud cake, and discharged water forms slurry tail water;
step 3: preparing flowing backfill, namely mixing coarse aggregate and fine aggregate in the step 1 with dehydrated mud cakes in the step 2 to form an aggregate mixture, and mixing slurry tail water generated in the step 2 with cement, fly ash, a water reducing agent and a coagulant to form a gel mixture, and stirring the aggregate mixture and the gel mixture to prepare the flowing backfill.
Preferably, the step 1 specifically includes the following steps:
step 1.1: the shield waste slurry in the slurry tank is conveyed into a roller screening machine through a slurry pump, the aperture of the roller screening machine is 5mm, and coarse aggregate with the particle size of more than 5mm is obtained after screening the waste slurry;
step 1.2: the rest waste slurry after screening is conveyed into a cyclone, aggregate with the particle size of 0.5-5 mm is separated by the cyclone, internal-rotation slurry with the particle size of less than 0.5mm is discharged from the upper part of the cyclone, and external-rotation slurry with the particle size of 0.5-5 mm is discharged from the lower part of the cyclone and enters a dewatering screen;
step 1.3: the aperture of the screen mesh of the dewatering screen is 0.5mm, and the dewatering screen can dewater and screen aggregate in the external cyclone slurry to obtain fine aggregate with the particle size of 0.5-5 mm;
step 1.4: the slurry screened by the dewatering screen is mixed with the internal rotation slurry to form uniform slurry with uniform components.
Preferably, the step 2 specifically includes the following steps:
step 2.1: the uniform slurry in the step 1 is conveyed to a flocculation conditioning tank, a flocculating agent is added to the uniform slurry to coagulate and settle suspended particles in the uniform slurry, the flocculating agent is anionic polyacrylamide, the mass concentration of the flocculating agent is 0.02-0.03%, a stirrer in the flocculation conditioning tank is opened for stirring and mixing after the flocculating agent is added, the mixing stage is carried out for 2-3 min at the speed of 600-700 r/min, the flocculating agent and the solution are uniformly mixed, and the flocculation settlement time is 10-15min;
step 2.2: and conveying the flocculated and conditioned slurry to a vacuum preloading device through a slurry pump to perform vacuum preloading to form a dehydrated mud cake, wherein water discharged from the vacuum preloading is slurry tail water.
Preferably, the vacuum preloading apparatus includes: the top of the box body is provided with a vacuum film, the vacuum film isolates the inside of the box body into a closed space, and the lower part of the box body is provided with a mud input port; the drainage plate is arranged in the closed space of the box body, the outer side of the drainage plate is wrapped by geotechnical cloth, and a plurality of water permeable holes are formed in the drainage plate; and the drain pipes are correspondingly communicated with the water permeable holes on the plurality of drain plates, and are connected with the vacuum pump outside the box body.
Preferably, the step 3 specifically includes the following steps:
step 3.1: uniformly mixing the coarse aggregate and the fine aggregate generated in the step 1 with the dehydrated mud cake formed in the step 2, wherein the mixing mass ratio of the dehydrated mud cake to the fine aggregate to the coarse aggregate is 1:1.7-2.8:2.5-4.5, and the three materials are mixed in proportion to form an aggregate mixture;
step 3.2: mixing the slurry tail water generated in the step 2 with cement, fly ash, a water reducing agent and a coagulant, wherein the mixing mass ratio of the cement, the fly ash, the water reducing agent, the coagulant to the slurry tail water is 1:0.9-1.2:0.04-0.06:0.02-0.03:0.6-2.0, and the four materials and the slurry tail water are stirred to form a gel mixture;
step 3.3: and (3) placing the aggregate mixture formed in the step (3.1) and the gel mixture formed in the step (3.2) into a mortar stirrer according to the mass ratio of 1.5-1.9:1, stirring for 4-6 min, and preparing the flowing backfill.
Preferably, the water reducing agent in the step 3.2 is composed of one or two of a phosphate-based water reducing agent and a polycarboxylate water reducing agent, and the coagulant is composed of one or two of sodium silicate and calcium formate.
The invention at least comprises the following beneficial effects:
aiming at the difficult problems that the components of the construction waste slurry are complex and difficult to treat and utilize, the application develops a preparation process of the flowing backfill based on the shield waste slurry, and the preparation process has the following outstanding advantages:
(1) In the aspect of recycling the shield waste mud, compared with the traditional mode of taking the mud as building materials, roadbed materials and agricultural soil, the application provides a novel waste mud recycling method, which fully utilizes aggregates with different sizes and tail water in the mud and realizes the green disposal of wastes;
(2) In the aspect of multistage separation of waste mud, coarse aggregate and fine aggregate are separated by adopting a method of gradually separating a drum screen, a cyclone and a dewatering screen, and are added in proportion when preparing flowing backfill, and compared with the method of directly mixing mud and a curing agent, the method can ensure the strength and the fluidity of backfill materials;
(3) In the aspect of flocculating and dehydrating the slurry, the slurry is treated by adopting a flocculating conditioning-vacuum preloading method, and the flocculating conditioning agent adopts anionic polyacrylamide, so that the slurry flocculating effect is better; the vacuum preloading method commonly used in soft foundation reinforcement engineering is applied to slurry dehydration, the dehydrated slurry cake is not hardened, the subsequent stirring is more facilitated, and the energy consumption of the vacuum preloading method is lower than that of a conventional plate-and-frame filter press;
(4) In the aspect of preparation of the flowing backfill, the novel water reducing agent and the coagulant are adopted, and the mixture is mixed according to the optimal proportion of each material, so that the prepared flowing backfill has higher fluidity and compressive strength, and has better performance advantage than the backfill material of common pipe ditch and retaining wall back backfill engineering.
The preparation process of the flowing backfill based on the shield waste mud realizes the full utilization of particles with different sizes and tail water in the waste mud, the 28d unconfined compressive strength of the prepared flowing backfill is above 350kPa, the flowing value is above 200mm, and the flowing backfill can be applied to backfill engineering of pipe ditches and retaining walls.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention.
Drawings
FIG. 1 is a flow chart of a process for preparing a flowing backfill based on shield waste mud;
FIG. 2 is a schematic diagram of the vacuum preloading apparatus of the present invention.
Reference numerals illustrate: 1-box, 2-vacuum membrane, 3-mud input port, 4-drain board, 5-geotechnical cloth, 6-drain pipe, 7-vacuum pump.
Detailed Description
The present invention is described in further detail below with reference to the drawings to enable those skilled in the art to practice the invention by referring to the description.
It should be noted that the experimental methods described in the following embodiments, unless otherwise specified, are all conventional methods, and the reagents and materials, unless otherwise specified, are all commercially available; in the description of the present invention, the terms "transverse", "longitudinal", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, are merely for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus are not to be construed as limiting the present invention.
As shown in FIG. 1, the invention provides a preparation process of a flowing backfill based on shield waste mud, which mainly comprises the following steps: (1) multistage separation of waste mud; (2) flocculating and dehydrating the slurry; (3) preparation of a flowing backfill. The specific operation steps of each process are as follows.
Step 1: multistage separation of waste mud
The components of the shield waste mud are complex, the shield waste mud contains broken stone, coarse sand, fine sand, clay particles and the like, the waste mud is treated in a multistage separation mode, materials with different components are obtained, and the screening of aggregate in the waste mud is realized. In order to achieve the aim, equipment used in the step comprises a roller screening machine, a cyclone and a dewatering screen. And (3) conveying the shield waste slurry in the slurry tank to a roller screening machine through a slurry pump, wherein the aperture of the roller screening machine is 5mm, and screening the slurry to obtain coarse aggregate with the particle size of more than 5 mm. The sieved slurry is conveyed into a cyclone, aggregate with the particle size of 0.5-5 mm can be separated by the cyclone, internal-rotation slurry with the particle size of less than 0.5mm is discharged from the upper part of the cyclone, and external-rotation slurry with the particle size of 0.5-5 mm is discharged from the lower part of the cyclone and enters a dewatering screen. The aperture of the screen mesh of the dewatering screen is 0.5mm, and the dewatering screen can dewater and screen aggregate in the external swirling slurry to obtain fine aggregate with the particle size of 0.5-5 mm. The slurry screened by the dewatering screen is mixed with the internal rotation slurry to form slurry with uniform components. The waste mud is subjected to multistage separation to obtain coarse aggregate, fine aggregate and uniform mud, and the preparation of flowing backfill is carried out according to a certain proportion after the aggregate is separated, so that the waste mud has good strength and fluidity.
Step 2: mud flocculation dehydration
Treating the slurry after multistage separation by adopting a flocculation conditioning-vacuum preloading method, after the slurry is conveyed to a flocculation conditioning tank, adding a flocculating agent into the slurry to coagulate and settle suspended particles in the slurry, wherein the flocculating agent is anionic polyacrylamide, adding the flocculating agent to ensure that the mass concentration of the flocculating agent is 0.02-0.03%, opening a stirrer in the conditioning tank after adding the flocculating agent, stirring for 2-3 min at the speed of 600-700 r/min in a mixing stage to ensure that the flocculating agent is quickly and uniformly mixed with the solution, flocculating settling time is 10-15min, and stopping stirring in the flocculation stage to prevent the stirrer from breaking up the flocs. The mud after flocculation conditioning is conveyed to a vacuum preloading device through a mud pump, as shown in fig. 2, the vacuum preloading device consists of a box body 1, a vacuum membrane 2, a vacuum pump 7, a drain board 4, a drain pipe 6, geotechnical cloth 5 and a mud input port 3, the box body 1 and the vacuum membrane 2 form a closed space for storing mud, the surface of the drain board 4 is provided with water permeable holes, the geotechnical cloth 5 is wrapped on the outer side of the drain board 4 and is used for isolating mud particles, and the drain board 4 is connected with the drain pipe 6 and is used for extracting water in the mud. The vacuum pump 7 is opened, the air pressure of the closed space formed by the box body 1 and the vacuum membrane 2 is gradually reduced, water in the slurry passes through the geotechnical cloth 5 to be in the drain board 4 under the action of atmospheric pressure, and the water in the drain board 4 flows out to the tail water tank through the drain pipe 6. Compared with the traditional plate-frame filter pressing dehydration, the mud cake can not harden after the dehydration by the vacuum preloading method, is more beneficial to the mixing of subsequent materials, and has lower energy consumption than the filter pressing dehydration.
Step 3: preparation of flowable backfill
Uniformly mixing the coarse aggregate and the fine aggregate generated in the step 1 with the dehydrated mud cake in the step 2, wherein the mixing mass ratio of the dehydrated mud cake to the fine aggregate to the coarse aggregate is 1:1.7-2.8:2.5-4.5, and the three materials are mixed according to a proportion to form an aggregate mixture. Mixing the slurry tail water generated in the step 2 with cement, fly ash, a water reducing agent and a coagulant, wherein the water reducing agent mainly comprises one or two of a phosphate water reducing agent and a polycarboxylate water reducing agent, the coagulant mainly comprises one or two of sodium silicate and calcium formate, the mixing mass ratio of the cement, the fly ash, the water reducing agent, the coagulant and the slurry tail water is 1:0.9-1.2:0.04-0.06:0.02-0.03:0.6-2.0, and the four materials and the tail water are stirred into a gel mixture. And then placing the aggregate mixture and the gel mixture into a mortar stirrer according to the mass ratio of 1.5-1.9:1, stirring for 4-6 min, and preparing the flowing backfill. The water reducing agent and the coagulant are made of novel materials, and are mixed according to an optimal proportion, so that the prepared flowing backfill has better strength and fluidity.
Example 1
The shield waste mud is generated in the construction process of a tunnel project passing through river in Nanjing, the length of a shield tunnel part is 3537m, a circular slurry shield machine with the diameter of 14.93m is adopted for excavation and tunneling, and the waste mud is generated in the construction process by about 86 ten thousand m 3 . The mud is prepared by adding water into bentonite, clay and sodium carbonate, and the waste mud has strong alkalinity, large volume and large disposal difficulty. Setting up a mud temporary storage pool on a construction site, collecting waste mud, and simultaneously settling and removing part of water. Physical indexes of the shield waste mud are shown in table 1.
TABLE 1 physical Properties of Shield waste mud
The method adopts three steps of waste mud multistage separation, mud flocculation dehydration and flowing backfill preparation to treat the waste mud.
Step one: waste slurry temporarily stored in a slurry pond is guided into a screening system (a roller screening machine, a cyclone and a dewatering screen in sequence) through a conveying pump, and coarse aggregate with the size of more than 5mm, fine aggregate with the size of 0.5-5 mm and uniform slurry are separated.
Step two: conveying the uniform slurry into a flocculation conditioning tank, treating by adopting a flocculation conditioning-vacuum preloading method, adding anionic polyacrylamide into the conditioning tank to enable a flocculating agent to promote slurry particles to form flocs, adding the flocculating agent to enable the mass concentration of the slurry particles to be 0.02%, and opening a stirrer in the flocculation conditioning tank to stir and mix after adding the flocculating agent, wherein the mixing stage is stirring for 2min at a speed of 600 r/min. Then the mud is pumped into the vacuum preloading device through the mud input port 3, a closed space for storing the mud is formed by the box body 1 and the vacuum membrane 2, the vacuum pump 7 is operated, negative pressure is formed in the device, moisture in the mud passes through the geotechnical cloth 5 and enters the drain board 4, particles in the mud can be intercepted by the geotechnical cloth 5, the moisture in the drain board 4 is discharged through the drain pipe 6, discharged mud tail water is stored in a tail water tank, and a dehydrated mud cake in the device is taken out after the moisture is pumped to a certain degree.
Step three: and (3) stirring and mixing the coarse aggregate and the fine aggregate in the step one and the dehydrated mud cake in the step two to form an aggregate mixture. And step two, mixing the slurry tail water, cement, fly ash, a water reducing agent, a coagulant and the like to form a gel mixture. And (3) stirring the aggregate mixture and the gel mixture in a mortar stirrer for 5min according to the mass ratio of 1.6:1 to obtain the flowing backfill. The composition of the flowable backfill is shown in Table 2.
TABLE 2 parts by weight of the components in the flowing backfill
| Component (A) | Parts by weight | Component (A) | Parts by weight |
| Coarse aggregate | 386 | Fly ash | 308 |
| Fine aggregate | 209 | Water reducing agent | 15.2 |
| Dehydrated mud cake | 100 | Coagulant agent | 7.8 |
| Cement and its preparation method | 330 | Slurry tail water | 430 |
Example 2
The shield waste slurry is generated in the construction process of a tunnel project at the bottom of a certain lake in Wuhan, the length of a shield tunnel part is 5712m, a circular slurry shield machine with the diameter of 15.06m is adopted for excavation and tunneling, and the waste slurry is generated in the construction process by about 157 ten thousand m 3 . The mud is prepared by adding bentonite, clay and sodium hydroxide into water, and the waste mud has strong alkalinity, large volume and large disposal difficulty. Setting up a mud temporary storage pool on a construction site, collecting waste mud, and simultaneously settling and removing part of water. Physical indexes of the shield waste mud are shown in Table 3Shown.
TABLE 3 physical indices of shield waste mud
The method adopts three steps of waste mud multistage separation, mud flocculation dehydration and flowing backfill preparation to treat the waste mud.
Step one: waste mud temporarily stored in the mud pit is led into a screening system through a conveying pump to separate coarse aggregate with the size of more than 5mm, fine aggregate with the size of 0.5-5 mm and uniform mud.
Step two: conveying the uniform slurry into a flocculation conditioning tank, treating by adopting a flocculation conditioning-vacuum preloading method, adding anionic polyacrylamide into the conditioning tank to enable a flocculating agent to promote slurry particles to form flocs, adding the flocculating agent to enable the mass concentration of the slurry particles to be 0.03%, and opening a stirrer in the flocculation conditioning tank to stir and mix after adding the flocculating agent, wherein the mixing stage is stirred at a speed of 700r/min for 3min. Then the mud is pumped into the vacuum preloading device through the mud input port 3, a closed space for storing the mud is formed by the box body 1 and the vacuum membrane 2, the vacuum pump 7 is operated, negative pressure is formed in the device, moisture in the mud passes through the geotechnical cloth 5 and enters the drain board 4, particles in the mud can be intercepted by the geotechnical cloth 5, the moisture in the drain board 4 is discharged through the drain pipe 6, discharged tail water is stored in a tail water tank, and a dehydrated mud cake in the device is taken out after the moisture is pumped to a certain degree.
Step three: and (3) stirring and mixing the coarse aggregate and the fine aggregate in the step one and the dehydrated mud cake in the step two to form an aggregate mixture. And step two, mixing the slurry tail water, cement, fly ash, a water reducing agent, a coagulant and the like to form a gel mixture. And (3) stirring the aggregate mixture and the gel mixture in a mortar stirrer for 5min according to the mass ratio of 1.9:1 to obtain the flowing backfill. The composition of the flowable backfill is shown in Table 4.
TABLE 4 parts by weight of the components in the flowing backfill
| Component (A) | Parts by weight | Component (A) | Parts by weight |
| Coarse aggregate | 415 | Fly ash | 285 |
| Fine aggregate | 237 | Water reducing agent | 15.4 |
| Dehydrated mud cake | 100 | Coagulant agent | 7.9 |
| Cement and its preparation method | 306 | Slurry tail water | 415 |
Comparative example 1:
selecting shield waste slurry (the physical index of which is the same as that of the waste slurry in embodiment 1) of a certain tunnel engineering, directly pouring the slurry into a stirrer, stirring for 2min, adding cement, fly ash, a water reducing agent and a coagulant, and stirring uniformly again to obtain the flowing backfill. The composition of the flowable backfill is shown in Table 5.
TABLE 5 parts by weight of the components in the flowing backfill
| Component (A) | Parts by weight | Component (A) | Parts by weight |
| Waste mud | 950 | Water reducing agent | 4.3 |
| Cement and its preparation method | 104 | Coagulant agent | 2.1 |
| Fly ash | 94 |
Comparative example 2:
selecting shield waste slurry (the physical index of which is the same as that of the waste slurry in the embodiment 2) of a certain tunnel engineering, directly pouring the slurry into a stirrer, stirring for 2min, adding cement, fly ash, a water reducing agent and a coagulant, and stirring uniformly again to obtain the flowing backfill. The composition of the flowable backfill is shown in Table 6.
TABLE 6 parts by weight of the components in the flowing backfill
| Component (A) | Parts by weight | Component (A) | Parts by weight |
| Waste mud | 1080 | Water reducing agent | 4.2 |
| Cement and its preparation method | 116 | Coagulant agent | 2.5 |
| Fly ash | 98 |
Comparative example 3:
the preparation was carried out in step three of example 1 using the coarse aggregate, the fine aggregate and the dehydrated cake of example 1 as raw materials, to obtain a flowable backfill. The composition of the flowable backfill is shown in Table 7.
TABLE 7 parts by weight of the components in the flowback backfill
| Component (A) | Parts by weight | Component (A) | Parts by weight |
| Coarse aggregate | 280 | Fly ash | 308 |
| Fine aggregate | 280 | Water reducing agent | 15.2 |
| Dehydrated mud cake | 140 | Coagulant agent | 7.8 |
| Cement and its preparation method | 330 | Slurry tail water | 430 |
Comparative example 4:
the preparation was carried out in step three of example 1 using the coarse aggregate, the fine aggregate and the dehydrated cake of example 1 as raw materials, to obtain a flowable backfill. The composition of the flowable backfill is shown in Table 8.
TABLE 8 parts by weight of the components in the flowing backfill
| Component (A) | Parts by weight | Component (A) | Parts by weight |
| Coarse aggregate | 420 | Fly ash | 308 |
| Fine aggregate | 140 | Water reducing agent | 15.2 |
| Dehydrated mud cake | 140 | Coagulant agent | 7.8 |
| Cement and its preparation method | 330 | Slurry tail water | 430 |
Comparative example 5:
the preparation was carried out in step three of example 1 using the coarse aggregate, the fine aggregate and the dehydrated cake of example 1 as raw materials, to obtain a flowable backfill. The composition of the flowable backfill is shown in Table 9.
TABLE 9 parts by weight of the components in the flowback backfill
| Component (A) | Parts by weight | Component (A) | Parts by weight |
| Coarse aggregate | 350 | Fly ash | 308 |
| Fine aggregate | 175 | Water reducing agent | 15.2 |
| Dehydrated mud cake | 175 | Coagulant agent | 7.8 |
| Cement and its preparation method | 330 | Slurry tail water | 430 |
Performance test:
seven sets of flow back fillers were tested for performance and the test results are shown in table 10.
Table 10 results of performance test of seven flowing backfill materials
As can be seen from the above Table 10, the 28d unconfined compressive strength of the flowable backfill prepared by the process of examples 1 and 2 herein was above 350kPa, the flow value was above 200mm, and the performance was much higher in all respects than that of the flowable backfill prepared by the process of comparative examples 1, 2, 3, 4 and 5.
Although embodiments of the present invention have been disclosed above, it is not limited to the details and embodiments shown and described, it is well suited to various fields of use for which the invention would be readily apparent to those skilled in the art, and accordingly, the invention is not limited to the specific details and illustrations shown and described herein, without departing from the general concepts defined in the claims and their equivalents.
Claims (6)
1. The preparation process of the flowing backfill based on the shield waste slurry is characterized by comprising the following three steps:
step 1: multistage separation is carried out on the waste slurry, and aggregates in the waste slurry are screened to obtain coarse aggregates, fine aggregates and uniform slurry obtained by mixing;
step 2: the slurry is flocculated and dehydrated, the uniform slurry after multistage separation is treated by adopting a flocculation conditioning and vacuum preloading method to form a dehydrated mud cake, and discharged water forms slurry tail water;
step 3: preparing flowing backfill, namely mixing coarse aggregate and fine aggregate in the step 1 with dehydrated mud cakes in the step 2 to form an aggregate mixture, and mixing slurry tail water generated in the step 2 with cement, fly ash, a water reducing agent and a coagulant to form a gel mixture, and stirring the aggregate mixture and the gel mixture to prepare the flowing backfill.
2. The process for preparing the flowing backfill based on shield waste mud according to claim 1, wherein the step 1 specifically comprises the following steps:
step 1.1: the shield waste slurry in the slurry tank is conveyed into a roller screening machine through a slurry pump, the aperture of the roller screening machine is 5mm, and coarse aggregate with the particle size of more than 5mm is obtained after screening the waste slurry;
step 1.2: the rest waste slurry after screening is conveyed into a cyclone, aggregate with the particle size of 0.5-5 mm is separated by the cyclone, internal-rotation slurry with the particle size of less than 0.5mm is discharged from the upper part of the cyclone, and external-rotation slurry with the particle size of 0.5-5 mm is discharged from the lower part of the cyclone and enters a dewatering screen;
step 1.3: the aperture of the screen mesh of the dewatering screen is 0.5mm, and the dewatering screen can dewater and screen aggregate in the external cyclone slurry to obtain fine aggregate with the particle size of 0.5-5 mm;
step 1.4: the slurry screened by the dewatering screen is mixed with the internal rotation slurry to form uniform slurry with uniform components.
3. The process for preparing the flowing backfill based on shield waste mud according to claim 1, wherein the step 2 specifically comprises the following steps:
step 2.1: the uniform slurry in the step 1 is conveyed to a flocculation conditioning tank, a flocculating agent is added to the uniform slurry to coagulate and settle suspended particles in the uniform slurry, the flocculating agent is anionic polyacrylamide, the mass concentration of the flocculating agent is 0.02-0.03%, a stirrer in the flocculation conditioning tank is opened for stirring and mixing after the flocculating agent is added, the mixing stage is carried out for 2-3 min at the speed of 600-700 r/min, the flocculating agent and the solution are uniformly mixed, and the flocculation settlement time is 10-15min;
step 2.2: and conveying the flocculated and conditioned slurry to a vacuum preloading device through a slurry pump to perform vacuum preloading to form a dehydrated mud cake, wherein water discharged from the vacuum preloading is slurry tail water.
4. A shield-waste-slurry-based flowable backfill preparation process as claimed in claim 3, wherein the vacuum preloading means comprises:
the top of the box body is provided with a vacuum film, the vacuum film isolates the inside of the box body into a closed space, and the lower part of the box body is provided with a mud input port;
the drainage plate is arranged in the closed space of the box body, the outer side of the drainage plate is wrapped by geotechnical cloth, and a plurality of water permeable holes are formed in the drainage plate;
and the drain pipes are correspondingly communicated with the water permeable holes on the plurality of drain plates, and are connected with the vacuum pump outside the box body.
5. The process for preparing the flowing backfill based on shield waste mud according to claim 1, wherein the step 3 specifically comprises the following steps:
step 3.1: uniformly mixing the coarse aggregate and the fine aggregate generated in the step 1 with the dehydrated mud cake formed in the step 2, wherein the mixing mass ratio of the dehydrated mud cake to the fine aggregate to the coarse aggregate is 1:1.7-2.8:2.5-4.5, and the three materials are mixed in proportion to form an aggregate mixture;
step 3.2: mixing the slurry tail water generated in the step 2 with cement, fly ash, a water reducing agent and a coagulant, wherein the mixing mass ratio of the cement, the fly ash, the water reducing agent, the coagulant to the slurry tail water is 1:0.9-1.2:0.04-0.06:0.02-0.03:0.6-2.0, and the four materials and the slurry tail water are stirred to form a gel mixture;
step 3.3: and (3) placing the aggregate mixture formed in the step (3.1) and the gel mixture formed in the step (3.2) into a mortar stirrer according to the mass ratio of 1.5-1.9:1, stirring for 4-6 min, and preparing the flowing backfill.
6. The preparation process of the flowing backfill based on shield waste slurry according to claim 5, wherein the water reducing agent in the step 3.2 is composed of one or two of phosphate-based water reducing agent and polycarboxylate water reducing agent, and the accelerator is composed of one or two of sodium silicate and calcium formate.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN107381988A (en) * | 2017-08-16 | 2017-11-24 | 山东大学 | A kind of shield high concentration discards mud disposal system and method |
| CN212387854U (en) * | 2020-03-13 | 2021-01-22 | 中铁环境科技工程有限公司 | Shield constructs dregs mud-water separation system |
| CN114213077A (en) * | 2021-12-07 | 2022-03-22 | 华南理工大学 | Controllable low-strength material based on shield slurry and reclaimed sand powder and preparation method and application thereof |
| CN114436496A (en) * | 2022-01-27 | 2022-05-06 | 浙大城市学院 | Microwave heating vacuum preloading sludge dewatering device and construction method |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107381988A (en) * | 2017-08-16 | 2017-11-24 | 山东大学 | A kind of shield high concentration discards mud disposal system and method |
| CN212387854U (en) * | 2020-03-13 | 2021-01-22 | 中铁环境科技工程有限公司 | Shield constructs dregs mud-water separation system |
| CN114213077A (en) * | 2021-12-07 | 2022-03-22 | 华南理工大学 | Controllable low-strength material based on shield slurry and reclaimed sand powder and preparation method and application thereof |
| CN114436496A (en) * | 2022-01-27 | 2022-05-06 | 浙大城市学院 | Microwave heating vacuum preloading sludge dewatering device and construction method |
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