CN115478880B - Construction method for reducing rebound rate of sprayed concrete - Google Patents
Construction method for reducing rebound rate of sprayed concrete Download PDFInfo
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- CN115478880B CN115478880B CN202211294208.XA CN202211294208A CN115478880B CN 115478880 B CN115478880 B CN 115478880B CN 202211294208 A CN202211294208 A CN 202211294208A CN 115478880 B CN115478880 B CN 115478880B
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- 239000011378 shotcrete Substances 0.000 title claims abstract description 98
- 238000010276 construction Methods 0.000 title claims abstract description 60
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 86
- 238000005507 spraying Methods 0.000 claims abstract description 46
- 239000000203 mixture Substances 0.000 claims abstract description 18
- 238000012360 testing method Methods 0.000 claims abstract description 16
- 239000004568 cement Substances 0.000 claims abstract description 12
- 239000003795 chemical substances by application Substances 0.000 claims abstract description 11
- 230000004927 fusion Effects 0.000 claims abstract description 11
- 239000000463 material Substances 0.000 claims abstract description 8
- 239000003638 chemical reducing agent Substances 0.000 claims abstract description 5
- 238000005303 weighing Methods 0.000 claims abstract description 4
- 239000004567 concrete Substances 0.000 claims description 35
- 229910000831 Steel Inorganic materials 0.000 claims description 32
- 239000010959 steel Substances 0.000 claims description 32
- 238000002156 mixing Methods 0.000 claims description 28
- 238000000034 method Methods 0.000 claims description 24
- 239000002002 slurry Substances 0.000 claims description 15
- 239000010410 layer Substances 0.000 claims description 11
- 230000003014 reinforcing effect Effects 0.000 claims description 9
- 238000002347 injection Methods 0.000 claims description 7
- 239000007924 injection Substances 0.000 claims description 7
- 239000011435 rock Substances 0.000 claims description 6
- 238000004140 cleaning Methods 0.000 claims description 3
- 239000003292 glue Substances 0.000 claims description 3
- 238000002360 preparation method Methods 0.000 claims description 3
- 239000008262 pumice Substances 0.000 claims description 3
- 239000004576 sand Substances 0.000 claims description 3
- 239000007921 spray Substances 0.000 claims description 3
- 238000003756 stirring Methods 0.000 claims description 3
- 238000005553 drilling Methods 0.000 claims description 2
- 230000000694 effects Effects 0.000 claims description 2
- 239000011241 protective layer Substances 0.000 claims description 2
- 238000004080 punching Methods 0.000 claims description 2
- 238000011065 in-situ storage Methods 0.000 claims 1
- 238000013101 initial test Methods 0.000 claims 1
- 239000002994 raw material Substances 0.000 abstract description 2
- 239000013078 crystal Substances 0.000 description 5
- 229910001653 ettringite Inorganic materials 0.000 description 5
- 229910001294 Reinforcing steel Inorganic materials 0.000 description 4
- 229920002678 cellulose Polymers 0.000 description 3
- 239000001913 cellulose Substances 0.000 description 3
- 230000007547 defect Effects 0.000 description 3
- 239000000523 sample Substances 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 229910004298 SiO 2 Inorganic materials 0.000 description 1
- 238000009412 basement excavation Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 description 1
- 239000000920 calcium hydroxide Substances 0.000 description 1
- 229910001861 calcium hydroxide Inorganic materials 0.000 description 1
- 239000002041 carbon nanotube Substances 0.000 description 1
- 229910021393 carbon nanotube Inorganic materials 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- VTHJTEIRLNZDEV-UHFFFAOYSA-L magnesium dihydroxide Chemical compound [OH-].[OH-].[Mg+2] VTHJTEIRLNZDEV-UHFFFAOYSA-L 0.000 description 1
- 239000000347 magnesium hydroxide Substances 0.000 description 1
- 229910001862 magnesium hydroxide Inorganic materials 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000002787 reinforcement Effects 0.000 description 1
- 238000009991 scouring Methods 0.000 description 1
Classifications
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D11/00—Lining tunnels, galleries or other underground cavities, e.g. large underground chambers; Linings therefor; Making such linings in situ, e.g. by assembling
- E21D11/04—Lining with building materials
- E21D11/10—Lining with building materials with concrete cast in situ; Shuttering also lost shutterings, e.g. made of blocks, of metal plates or other equipment adapted therefor
- E21D11/105—Transport or application of concrete specially adapted for the lining of tunnels or galleries ; Backfilling the space between main building element and the surrounding rock, e.g. with concrete
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D11/00—Lining tunnels, galleries or other underground cavities, e.g. large underground chambers; Linings therefor; Making such linings in situ, e.g. by assembling
- E21D11/14—Lining predominantly with metal
- E21D11/15—Plate linings; Laggings, i.e. linings designed for holding back formation material or for transmitting the load to main supporting members
- E21D11/152—Laggings made of grids or nettings
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D11/00—Lining tunnels, galleries or other underground cavities, e.g. large underground chambers; Linings therefor; Making such linings in situ, e.g. by assembling
- E21D11/38—Waterproofing; Heat insulating; Soundproofing; Electric insulating
Landscapes
- Engineering & Computer Science (AREA)
- Structural Engineering (AREA)
- Mining & Mineral Resources (AREA)
- Architecture (AREA)
- Civil Engineering (AREA)
- Life Sciences & Earth Sciences (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Geology (AREA)
- On-Site Construction Work That Accompanies The Preparation And Application Of Concrete (AREA)
- Pit Excavations, Shoring, Fill Or Stabilisation Of Slopes (AREA)
Abstract
A construction method for reducing rebound rate of sprayed concrete relates to the technical field of sprayed concrete support in a subsurface tunnel, and specifically comprises the following steps: testing and detecting coarse aggregate, fine aggregate, cement, accelerator, water reducing agent and mixture fusion agent on a construction site, and ensuring that the performance of the cement, the accelerator, the water reducing agent and the mixture fusion agent is qualified; the water content of aggregate is actually measured on site, the construction proportion is adjusted according to actual conditions to meet design requirements, then the material is weighed and fed through an automatic electronic weighing system, and before the construction of sprayed concrete, the sprayed surface is treated, the construction of sprayed concrete is carried out, the sprayed surface is leveled, the back cavity and leakage grouting are carried out; according to the invention, the mixture fusion agent is added into the raw materials of the original sprayed concrete, so that the early strength and the spraying performance of the sprayed concrete are greatly improved, the use cost is reduced, the adhesion between layers and the spraying compactness are improved by adopting a layered spraying mode, and meanwhile, the surface of the square spade is repaired, and the surface flatness is improved.
Description
Technical Field
The invention relates to the technical field of shotcrete support in a subsurface tunnel, in particular to a construction method for reducing the rebound rate of shotcrete.
Background
It is known that an essential procedure in the construction process of a subsurface excavation project, namely an initial support, wherein the construction of shotcrete is an important procedure of the initial support; the ideal consumption coefficient of the sprayed concrete is 1.8-2.0 times of the net quantity of the designed linear meter, but in the implementation process, the actual consumption of the sprayed concrete can reach about 2.5 times of the net quantity of the designed linear meter due to the influence of factors such as poor geological conditions, hydrogeological conditions, ground stability, mechanical equipment, manual proficiency and the like, so that the project cost is extremely unfavorable to control, and a great amount of capital consumption is caused.
Disclosure of Invention
In order to overcome the defects in the background art, the invention discloses a construction method for reducing the rebound rate of sprayed concrete.
In order to achieve the aim of the invention, the invention adopts the following technical scheme:
The construction method for reducing the rebound rate of the sprayed concrete specifically comprises the following steps:
(1) Testing and detecting coarse aggregate, fine aggregate, cement, accelerator, water reducer and mixture fusion agent on a construction site, ensuring that the performance of the construction site is qualified, and configuring a mixing ratio meeting the design strength and injection process requirements;
(2) The water content of the aggregate is measured on site by adopting concentrated mixing before construction, the actual water content of the aggregate is measured by taking the water content in the designed mixing proportion as a standard, the weight of the water in the aggregate is calculated, and the weight of the water in the actual aggregate is subtracted from the weight of the water in the designed mixing proportion, namely the weight of the water in the actual aggregate is required to be added during the mixing period;
(3) After the water content is actually measured on site, the construction proportion is adjusted according to the actual situation to meet the design requirement, then the materials are weighed and fed through an automatic electronic weighing system, the mixing time of the mixture is not less than 120s, and the mixture is placed into a concrete transport vehicle after the mixing is finished; meanwhile, the slump of the concrete is measured by adopting a slump barrel at the position of the stirring station, the slump meets the slump of the designed mixing proportion, and the concrete can be transported after being stirred uniformly;
(4) Before the construction of sprayed concrete, the sprayed surface is treated, and the method specifically comprises the following steps:
a. Before the sprayed concrete is implemented, cleaning up pumice, rock scraps and sundries on the sprayed surface, ensuring the safety of the sprayed concrete construction process, preventing the sprayed concrete from falling off, and enabling the sprayed concrete to be well bonded with the rock surface;
b. Burying a thick pile in the sprayed surface;
c. water seepage treatment is carried out on the sprayed surface;
(5) And (3) spraying concrete for construction: the spraying process is carried out from bottom to top in a segmented, segmented and layered mode, the initial spraying thickness is controlled to be 20-50 mm, the local concave cavity of the sprayed surface is backfilled, the side wall position is controlled to be 50-150 mm each time when the spraying process is carried out, the arch part is controlled to be 50-100 mm, and the spraying process is carried out after the sprayed concrete of the previous layer is finally solidified; the injection pressure is controlled to be 0.2-0.7 Mpa, and is adjusted according to the on-site trial injection effect; the nozzle is perpendicular to the sprayed surface, and the distance from the sprayed surface is preferably 0.6-1.5 m;
(6) Leveling the spraying surface: when the sprayed concrete is constructed to the last layer, the concrete thickness control pile is paid attention to at any time, and a square spade is adopted to shoveling off the sprayed concrete at the redundant part, so that the surface of the final sprayed concrete is smooth and has no macroscopic unevenness;
(7) Back cavity and leakage grouting treatment: after the sprayed concrete reaches 10Mpa, grouting holes with the diameter of 42mm are drilled along the surface of the sprayed concrete, the circumferential X longitudinal distance of the grouting holes is 2m X2 m along the sprayed surface, when the sprayed surface is free of water, the grouting depth is 30-50 mm, when the sprayed surface is discharged with water, the grouting depth is 200-300 mm, meanwhile, grouting is encrypted within the range of 3m of a leakage part, and grouting treatment is carried out on the cavity and the leakage water behind the sprayed concrete.
According to the construction method for reducing the rebound rate of the sprayed concrete, water is not added to the concrete in the concrete truck in the conveying process, and a concrete tank of the concrete truck is in an operating state.
According to the construction method for reducing the rebound rate of the sprayed concrete, on-site mixing ratio tests are required to be carried out on sprayed concrete materials in different batches, and the following data are referred to in the primary test: glue set ratio: 1:3.5-5; aggregate sand content: 45% -60%; water-to-gel ratio: 0.4 to 0.5; and after the preparation is finished, the sprayed concrete test block is standard-cultured for 28 days, and a compressive strength test is carried out to meet the design strength.
According to the construction method for reducing the rebound rate of the sprayed concrete, the thick piles are made of short steel bars, system anchor rods or primary support section steel; when the short steel bars are adopted, the short steel bars are driven into a sprayed surface, the exposed length is the thickness of sprayed concrete, and the longitudinal and circumferential distances are arranged according to 1.5m multiplied by 1.5m so as to ensure that the designed thickness of the sprayed concrete is as standard; when the system anchor rod is adopted, a concrete thickness spraying surface is marked at the exposed part of the system anchor rod, and the sprayed concrete thickness is controlled within the allowable range of the designed thickness; when the primary support section steel is adopted, the inner side of the primary support section steel is used as a control surface, and the thickness of a section steel protective layer is ensured to be enough.
According to the construction method for reducing the rebound rate of sprayed concrete, when the sprayed surface is provided with dotted or small strand water, a plurality of permeable blind pipes are embedded in the sprayed surface and are clung to the wall surface, the permeable blind pipes are clamped on the sprayed surface in a V shape through short steel bars or fixing wires by adopting hoses with diameters of 60-100 mm, and the steel bars are welded on the outer side of the section steel;
When the sprayed surface has strand-shaped or rain-shaped water outlet, the water outlet part is treated by the steps of: 1. increasing the number of the reinforcing mesh sheets, and paving double-layer reinforcing meshes or multiple layers of reinforcing meshes at the position; 2. a plastic waterproof board is paved behind the section steel, drainage is carried out on the rainy or stranded water outlet part, so that the water outlet of the sprayed surface is collected along the plastic waterproof board, and after the concrete has supporting strength, the back cavity is treated in a later period; 3. and (3) drilling a probe hole with the aperture of 40-80 mm obliquely upwards at the rear part of the finished primary support section, and punching the probe hole into the rear position of the sprayed surface to guide and discharge water.
According to the construction method for reducing the rebound rate of sprayed concrete, after the sprayed surface is treated, the construction site is leveled, the wet spraying mechanical arm, the air pipe, the water pipe, the cable line and the like are checked, good performance is ensured, the wet spraying mechanical arm is connected for trial spraying, and the parking position of the wet spraying mechanical arm is ensured to ensure that the rotary spray head of the mechanical arm can realize omnibearing spraying.
The construction method for reducing the rebound rate of the sprayed concrete is characterized in that grouting slurry is cement slurry, superfine cement slurry or double-slurry.
Due to the adoption of the technical scheme, the invention has the following beneficial effects:
1. According to the construction method for reducing the rebound rate of the sprayed concrete, the mixture fusion agent is added into the raw materials of the original sprayed concrete, and after the mixture fusion agent liquid is added, a large amount of rod-shaped ettringite crystals are precipitated from the slurry within a few minutes, the rod-shaped ettringite crystals and cellulose in the rod-shaped ettringite crystals are mutually connected to form a micro-reinforcement network structure, and meanwhile, a large amount of water is consumed for forming the rod-shaped ettringite, the slurry thickens, and the slurry is quickly coagulated under the combined action of the rod-shaped ettringite crystals and the cellulose, so that the rebound of the concrete is effectively prevented. Mg (OH) 2 in the mixture fusion agent provides crystal nucleus for the formation of C-S-H gel, promotes the crystallization of C-S-H in a large quantity, improves the strength, improves the early strength of sprayed concrete by 2-3 MPa, reduces the cement doping amount, greatly improves the early strength and the spraying performance of the sprayed concrete, and reduces the use cost.
2. According to the construction method for reducing the rebound rate of the sprayed concrete, disclosed by the invention, the water discharged from the sprayed surface is conducted to be drained or separated in advance, and the sprayed concrete is orderly collected and guided, so that the sprayed concrete is prevented from directly contacting with the sprayed concrete in a large area, the cohesiveness of the sprayed concrete, the section steel and the sprayed surface is prevented from being influenced, and the collapse and the falling block of the sprayed concrete caused by water flow scouring or water flow pressure are reduced; by grouting the cavity behind the sprayed concrete, the construction quality of the sprayed concrete is effectively ensured, and the leakage water is treated, so that the defect of a finished product in the later period is prevented.
3. According to the construction method for reducing the rebound rate of the sprayed concrete, disclosed by the invention, a layered spraying mode is adopted, so that the cohesiveness and spraying compactness between layers are improved, and meanwhile, the square spade is trimmed, and the surface flatness is improved.
Drawings
FIG. 1 is a schematic view of the lateral structure of the shotcrete thickness control and drainage of the water outlet according to the present invention.
FIG. 2 is a schematic view of a water permeable blind tube installation in a lateral direction according to the present invention.
Fig. 3 is a longitudinal schematic view of the advanced drain hole of the present invention.
In the figure: 1. a system anchor rod; 2. section steel; 3. a sprayed surface; 4. a water outlet part; 5. leading the water draining hole; 6. spraying the concrete surface; 7. reinforcing steel bar meshes; 8. a drainage waterproof board; 9. short steel bars; 10. a permeable blind pipe; 11. a reinforcing steel bar fixing frame; 12. the paragraph has been supported.
Detailed Description
The invention will be explained in more detail by the following examples, the purpose of which is to protect all technical improvements within the scope of the invention.
The construction method for reducing the rebound rate of the sprayed concrete, which is described with reference to figures 1-3, specifically comprises the following steps:
(1) Testing and detecting coarse aggregate, fine aggregate, cement, accelerator, water reducer and mixture fusion agent on a construction site, ensuring that the performance of the construction site is qualified, and configuring a mixing ratio meeting the design strength and injection process requirements;
In which, the sprayed concrete materials of different batches are subjected to on-site mixing ratio tests, and the following data are referred to in the primary test: glue set ratio: 1:3.5-5; aggregate sand content: 45% -60%; water-to-gel ratio: 0.4 to 0.5; after the preparation is finished, the sprayed concrete test block is standard-cultured for 28 days, and a compressive strength test is carried out to meet the design strength; the mixture fusion agent is a tackifier produced by Yunnan Siback new material technology Co-efficient, and the main components of the mixture fusion agent are SiO 2、Ca(OH)2、CaO、Mg(OH)2, carbon nano tubes and cellulose;
(2) The water content of the aggregate is measured on site by adopting concentrated mixing before construction, the actual water content of the aggregate is measured by taking the water content in the designed mixing proportion as a standard, the weight of the water in the aggregate is calculated, and the weight of the water in the actual aggregate is subtracted from the weight of the water in the designed mixing proportion, namely the weight of the water in the actual aggregate is required to be added during the mixing period; the design of the mixing proportion is carried out in the dry state of the aggregate, and the aggregate is influenced by factors such as rain, snow and the like and is in a non-dry state during the actual construction, so that the water content of the aggregate is tested, and the aggregate comprises coarse aggregate and fine aggregate;
(3) After the water content is actually measured on site, the construction proportion is adjusted according to actual conditions to meet the design requirement, then the materials are weighed and fed through an automatic electronic weighing system, the mixing time of the mixture is not less than 120s, the mixture is placed into a concrete transport vehicle after the mixing is finished, water is not added in the conveying process, and a concrete tank of the concrete transport vehicle is in an operating state, so that good fluidity of the concrete is ensured; meanwhile, the slump of the concrete is measured by adopting a slump barrel at the position of the stirring station, the slump meets the slump of the designed mixing proportion, and the concrete can be transported after being stirred uniformly;
(4) Before the construction of sprayed concrete, the sprayed surface 3 is treated, and the method specifically comprises the following steps:
a. before the sprayed concrete is implemented, cleaning up pumice, rock scraps and sundries on the sprayed surface 3, ensuring the safety of the sprayed concrete construction process, preventing the blocks from falling off, and enabling the sprayed concrete to be well bonded with the rock surface;
b. Burying a thick pile in the sprayed surface 3; the thick pile adopts short steel bars 9, system anchor rods 1 or primary support section steel; when the short steel bars 9 are adopted, the short steel bars are driven into the sprayed surface 3, the exposed length is the thickness of sprayed concrete, and the longitudinal and circumferential spacing is arranged according to 1.5m multiplied by 1.5m so as to ensure that the designed thickness of the sprayed concrete is as standard; when the system anchor rod 1 is adopted, a concrete thickness spraying surface is marked at the exposed part of the system anchor rod 1, and the sprayed concrete thickness is controlled within the range of the designed thickness; when the primary support section steel 2 is adopted, the inner side of the primary support section steel 2 is taken as a control surface;
c. Water seepage treatment is carried out on the sprayed surface 3; when the sprayed surface 3 has dot-shaped or small strand-shaped water outlet, a plurality of permeable blind pipes 10 are embedded in the position of the sprayed surface 3 in a manner of clinging to the wall surface, the number of the permeable blind pipes 10 is laid in combination with the water outlet condition, the sprayed surface is clinged to the wall surface, water outlet drainage is conducted, local collapse and block dropping caused during construction of sprayed concrete are effectively avoided, the construction quality of the concrete is improved, the permeable blind pipes 10 are clamped on the sprayed surface in a V shape by adopting reinforcing steel bars with the diameter of 8mm, and the reinforcing steel bars are welded on the outer side of the profile steel 2;
When the sprayed surface 3 is in a strand shape or a rain shape and water is discharged, the sprayed concrete is hardly adhered to the sprayed surface under the influence of water flow impact or water pressure, and the water outlet part 4 is required to be treated at the moment, and the water outlet part 4 is treated by the following steps: 1. the number of the reinforcing mesh sheets 7 is increased, double-layer reinforcing meshes or multiple layers of reinforcing meshes are paved at the position, and the framework support in the sprayed concrete is improved; 2. a plastic drainage waterproof board 8 is paved behind the reinforcement fixing frame 11, drainage is conducted on the rainy or strand-shaped water outlet part, water outlet of the sprayed surface 3 is collected along the drainage waterproof board 8, direct contact between the water outlet and sprayed concrete is reduced, and after the concrete has supporting strength, back cavities are treated in a later period; 3. an advanced water discharge hole 5 is drilled obliquely above the rear of the supported section 12, the aperture is 40-80 mm, the advanced water discharge hole 5 is driven into the rear position of the sprayed surface 3, the water outlet condition is further detected through the exploratory hole, meanwhile, water outlet is intercepted behind the sprayed surface 3, and the water outlet of the sprayed surface 3 is reduced; after the sprayed surface 3 is treated, the construction site is parallel, and the wet spraying mechanical arm, the air pipe, the water pipe and the cable line are inspected, so that good performance is ensured, the wet spraying mechanical arm is connected for trial spraying, and the parking position of the wet spraying mechanical arm is required to ensure that the rotary spray head of the mechanical arm can realize omnibearing spraying;
(5) And (3) spraying concrete for construction: the method comprises the steps of sectioning, slicing and layering from bottom to top during spraying, controlling the initial spraying thickness to be 20-50 mm, backfilling local concave cavities of a sprayed surface 3, controlling the repeated spraying thickness of a side wall to be 50-150 mm each time during repeated spraying, controlling the repeated spraying thickness of an arch part to be 50-100 mm, and performing repeated spraying after the sprayed concrete of the previous layer is finally solidified, so that the sprayed concrete has enough strength and effective bonding among the sprayed concrete of each layer is ensured; the spraying pressure is 0.2-0.7 Mpa, the nozzle is perpendicular to the sprayed surface, and the distance from the sprayed surface is 0.6-1.5 m;
(6) Leveling the spraying surface: when the sprayed concrete is constructed to the last layer, the concrete thickness pile is noticed at any time, and a square spade is adopted to shoveling off the sprayed concrete at the redundant part, so that the surface 6 of the final sprayed concrete is smooth and has no macroscopic unevenness;
(7) Grouting treatment of the back cavity: after the sprayed concrete reaches 10Mpa, grouting holes with the diameter of phi 42mm are drilled along the sprayed concrete surface 6, the longitudinal spacing of the grouting holes is 2 x 2m along the circumferential direction of the sprayed surface, when the sprayed surface is free of water, the grouting depth is 30-50 mm, when the sprayed surface is water-out, the grouting depth is 200-300 mm, meanwhile, grouting is encrypted within the range of 3m of a leaking part, grouting treatment is carried out on the back cavity of the sprayed concrete and the leaking water, and grouting slurry is cement slurry, superfine cement slurry or double slurry which is used for guaranteeing the construction quality of the sprayed concrete and treating the leaking water, so that later-stage finished product defects are prevented.
The invention is not described in detail in the prior art.
The embodiments selected herein for the purposes of disclosing the invention are presently considered to be suitable, but it is to be understood that the invention is intended to include all such variations and modifications as fall within the spirit and scope of the invention.
Claims (5)
1. A construction method for reducing the rebound rate of sprayed concrete is characterized by comprising the following steps: the method specifically comprises the following steps:
(1) Testing and detecting coarse aggregate, fine aggregate, cement, accelerator, water reducer and mixture fusion agent on a construction site, ensuring that the performance of the construction site is qualified, and configuring a mixing ratio meeting the design strength and injection process requirements;
(2) The water content of the aggregate is measured on site by adopting concentrated mixing before construction, the actual water content of the aggregate is measured by taking the water content in the designed mixing proportion as a standard, the weight of the water in the aggregate is calculated, and the weight of the water in the actual aggregate is subtracted from the weight of the water in the designed mixing proportion, namely the weight of the water in the actual aggregate is required to be added during the mixing period;
(3) After the water content is actually measured on site, the construction proportion is adjusted according to the actual situation to meet the design requirement, then the materials are weighed and fed through an automatic electronic weighing system, the mixing time of the mixture is not less than 120s, and the mixture is placed into a concrete transport vehicle after the mixing is finished; meanwhile, the slump of the concrete is measured by adopting a slump barrel at the position of the stirring station, the slump meets the slump of the designed mixing proportion, and the concrete can be transported after being stirred uniformly;
(4) Before the construction of sprayed concrete, the sprayed surface is treated, and the method specifically comprises the following steps:
a. Before the sprayed concrete is implemented, cleaning up pumice, rock scraps and sundries on the sprayed surface, ensuring the safety of the sprayed concrete construction process, preventing the sprayed concrete from falling off, and enabling the sprayed concrete to be well bonded with the rock surface;
b. Burying a thick pile in the sprayed surface;
The thick pile adopts short steel bars, system anchor rods or primary support section steel; when the short steel bars are adopted, the short steel bars are driven into a sprayed surface, the exposed length is the thickness of sprayed concrete, and the longitudinal and circumferential distances are arranged according to 1.5m multiplied by 1.5m so as to ensure that the designed thickness of the sprayed concrete is as standard; when the system anchor rod is adopted, a concrete thickness spraying surface is marked at the exposed part of the system anchor rod, and the sprayed concrete thickness is controlled within the allowable range of the designed thickness; when the primary support section steel is adopted, the inner side of the primary support section steel is taken as a control surface, and the thickness of a section steel protective layer is ensured to be enough;
c. water seepage treatment is carried out on the sprayed surface;
When the sprayed surface is provided with dotted or small strand water, a plurality of permeable blind pipes are embedded in the sprayed surface and cling to the wall surface, the permeable blind pipes are clamped on the sprayed surface in a V shape through short steel bars or fixing wires by adopting hoses with diameters of 60-100 mm, and the steel bars are welded on the outer side of the section steel;
When the sprayed surface has strand-shaped or rain-shaped water outlet, the water outlet part is treated by the steps of: 1. increasing the number of the reinforcing mesh sheets, and paving double-layer reinforcing meshes or multiple layers of reinforcing meshes at the position; 2. a plastic waterproof board is paved behind the section steel, drainage is carried out on the rainy or stranded water outlet part, so that the water outlet of the sprayed surface is collected along the plastic waterproof board, and after the concrete has supporting strength, the back cavity is treated in a later period; 3. drilling a exploratory hole with the aperture of 40-80 mm at the rear inclined upper side of the finished primary support section, and punching the exploratory hole into the rear position of the sprayed surface to guide and discharge water;
(5) And (3) spraying concrete for construction: the spraying process is carried out from bottom to top in a segmented, segmented and layered mode, the initial spraying thickness is controlled to be 20-50 mm, the local concave cavity of the sprayed surface is backfilled, the side wall position is controlled to be 50-150 mm each time when the spraying process is carried out, the arch part is controlled to be 50-100 mm, and the spraying process is carried out after the sprayed concrete of the previous layer is finally solidified; the injection pressure is controlled to be 0.2-0.7 Mpa, and is adjusted according to the on-site trial injection effect; the nozzle is perpendicular to the sprayed surface, and the distance from the sprayed surface is preferably 0.6-1.5 m;
(6) Leveling the spraying surface: when the sprayed concrete is constructed to the last layer, the concrete thickness control pile is paid attention to at any time, and a square spade is adopted to shoveling off the sprayed concrete at the redundant part, so that the surface of the final sprayed concrete is smooth and has no macroscopic unevenness;
(7) Back cavity and leakage grouting treatment: after the sprayed concrete reaches 10Mpa, grouting holes with the diameter of 42mm are drilled along the surface of the sprayed concrete, the circumferential X longitudinal distance of the grouting holes is 2m X2 m along the sprayed surface, when the sprayed surface is free of water, the grouting depth is 30-50 mm, when the sprayed surface is discharged with water, the grouting depth is 200-300 mm, meanwhile, grouting is encrypted within the range of 3m of a leakage part, and grouting treatment is carried out on the cavity and the leakage water behind the sprayed concrete.
2. The construction method for reducing the rebound rate of sprayed concrete according to claim 1, wherein the construction method comprises the following steps: the mixing ratio test in the step (1) is as follows: in-situ mix tests are required for different batches of sprayed concrete materials, and the following data are referred to in the initial test: glue set ratio: 1 (3.5-5); aggregate sand content: 45% -60%; water-to-gel ratio: 0.4 to 0.5; and after the preparation is finished, the sprayed concrete test block is standard-cultured for 28 days, and a compressive strength test is carried out to meet the design strength.
3. The construction method for reducing the rebound rate of sprayed concrete according to claim 1, wherein the construction method comprises the following steps: and (3) adding water into the concrete in the concrete truck in the step (3) in the conveying process, wherein a concrete tank of the concrete truck is in an operating state.
4. The construction method for reducing the rebound rate of sprayed concrete according to claim 1, wherein the construction method comprises the following steps: after the sprayed surface is treated, the construction site is leveled, the wet spraying mechanical arm, the air pipe, the water pipe and the cable line are checked, the good performance is ensured, the wet spraying mechanical arm is connected for trial spraying, and the parking position of the wet spraying mechanical arm is required to ensure that the rotary spray head of the mechanical arm can realize omnibearing spraying.
5. The construction method for reducing the rebound rate of sprayed concrete according to claim 1, wherein the construction method comprises the following steps: the grouting slurry is cement slurry, superfine cement slurry or double slurry.
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