A method for roughening tunnel lining

Abstract

This invention relates to the field of tunnel lining construction technology and discloses a method for roughening tunnel lining construction, comprising the following steps: Step 1: Cleaning the inner surface of the lining concrete; Step 2: Roughening the surface of the lining concrete; Step 3: Pre-curing and humidifying the concrete to ensure it is fully saturated with water; Step 4: Ensuring the lining surface is surface dry with no standing water; Step 5: Applying a roughening coating; Step 6: Placing a moistened absorbent cloth to control humidity and cure the coating. This invention continuously sprays water onto the lining concrete before coating application to ensure it is fully saturated, reducing the absorption of moisture by the coating. Simultaneously, during curing, a moistened cloth is placed beside the coating to increase local air humidity through evaporation, inhibiting moisture loss from the coating. The combination of these two methods ensures uniform moisture loss and consistent shrinkage during coating curing, effectively avoiding shrinkage lines, pits, and cracks, and ensuring a smooth and flat coating surface.

Description

Technical Field

[0001] This invention relates to the field of tunnel lining construction technology, specifically a method for roughening tunnel lining construction. Background Technology

[0002] Tunnel lining roughness reduction is an important technical means to improve the flow capacity of water conveyance tunnels and reduce water conveyance energy consumption. After the construction of the tunnel concrete lining is completed, a roughness reduction coating is usually sprayed or brushed on the inner surface of the lining. By smoothing the lining surface, the surface roughness is reduced, thereby improving water conveyance efficiency and reducing head loss. The roughness reduction coating is generally composed of polymer resin materials, polyurea materials or modified epoxy materials, etc., which have good leveling and wear resistance. After being applied to the concrete surface, it can form a smooth protective layer.

[0003] In actual construction, after the concrete lining is poured, it still contains a certain amount of capillary pores and has a strong water absorption capacity. The concrete absorbs some of the moisture from the coating, leading to excessively rapid local water loss. At the same time, the outer surface of the coating is directly exposed to the tunnel air, and the internal moisture continues to evaporate and dissipate into the air. The uneven rate of water loss between the inside and outside causes uneven shrinkage of the coating during the curing process, ultimately manifesting as defects such as shrinkage lines, local pits, and even cracks on the coating surface. Therefore, we propose a method for roughening tunnel lining construction. Summary of the Invention

[0004] The purpose of this invention is to provide a method for reducing the roughness of tunnel lining. This method involves thoroughly humidifying the lining concrete before coating application to achieve a high water content saturation, thus reducing the absorption of moisture from the roughness-reducing coating. Simultaneously, during coating curing, a fully moistened absorbent cloth is placed beside the coating. The continuous evaporation of moisture from the cloth increases the local humidity around the coating, reducing the outward evaporation of moisture from within the coating. This prevents defects such as shrinkage, pitting, and cracking caused by excessive water loss, ultimately resulting in a smooth surface and excellent roughness-reducing effect, thus solving the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for roughening tunnel lining, comprising the following steps:

[0006] Step 1: Clean the inner surface of the tunnel lining concrete to remove surface dust, oil stains and attachments, and level any local protrusions.

[0007] Step 2: Roughen the surface of the cleaned lining concrete to form evenly distributed, densely packed micro-pits on the lining surface.

[0008] Step 3: Pre-curing and humidifying the roughened lining concrete by continuously spraying water onto the inner surface of the lining using spraying or watering equipment to ensure that the concrete fully absorbs water and reaches saturation.

[0009] Step 4: After the pre-curing and humidification are completed, stop spraying water and let it stand until the lining surface is dry and free of water accumulation.

[0010] Step 5: Apply a roughness-reducing coating to the surface of the lining concrete after it has dried.

[0011] Step Six: After the coating is applied, place a fully moistened absorbent cotton cloth next to the coating. The continuous evaporation of moisture from the cotton cloth will increase the humidity of the local space around the coating, thus moisturizing and maintaining the coating.

[0012] In a preferred embodiment of the present invention, the roughening treatment is performed by uniformly striking the surface of the lining concrete with a pointed hammer. The depth of the small pits formed by each strike is controlled to be 1 to 3 mm and the diameter is no more than 5 mm. The pits are evenly distributed on the lining surface.

[0013] In a preferred embodiment of the present invention, the pre-curing and humidification step involves spraying water at least three times a day, and the pre-curing and humidification lasts for 7 to 14 days.

[0014] In a preferred embodiment of the present invention, in the pre-curing and humidification step, when the moisture content of the measuring points on the lining surface is not less than 6%, the concrete is considered to have reached a sufficient degree of wetness.

[0015] In a preferred embodiment of the present invention, in step four, the settling time after stopping water spraying is 2 to 4 hours.

[0016] In a preferred embodiment of the present invention, the roughness-reducing coating is an epoxy roughness-reducing coating, a polyurea roughness-reducing coating, or a fluorine-modified polymer roughness-reducing protective coating, and the dry film thickness of the coating is 200-500 μm.

[0017] In a preferred embodiment of the present invention, the absorbent cotton cloth is a pure cotton fabric with a thickness of 3-8 mm and a width of 30-60 cm. Before use, the cotton cloth is soaked in clean water for no less than 30 minutes until it is moist but not dripping.

[0018] In a preferred embodiment of the present invention, the absorbent cotton cloth is vertically arranged next to the coating by a support member, with a distance of 5 to 15 cm between the cotton cloth and the coating surface, and the distance between adjacent cotton cloths not exceeding 2 m.

[0019] In a preferred embodiment of the present invention, the moisturizing and maintenance period is no less than 7 days, during which the cotton cloth is kept moist at all times, so that the relative humidity of the air in the local space around the coating is maintained at more than 70%.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] 1. This invention continuously sprays water to humidify the lining concrete before coating application, ensuring it is fully saturated with water and reducing the absorption of moisture by the coating. Simultaneously, during curing, a damp cotton cloth is placed next to the coating to increase local air humidity through evaporation, inhibiting moisture loss from the coating. The combination of these two methods ensures uniform moisture loss and consistent shrinkage during coating curing, effectively avoiding shrinkage lines, pits, and cracks, and ensuring a smooth and flat coating surface.

[0022] 2. This invention increases the contact area between the concrete surface and the roughening coating by creating dense micro-pits through hammering on the surface of the lining concrete, which significantly improves the adhesion between the coating and the concrete substrate and extends the service life of the coating. Attached Figure Description

[0023] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0024] Figure 1 This is a flowchart of a tunnel lining roughness reduction construction method according to the present invention. Detailed Implementation

[0025] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0026] Please see Figure 1 This invention provides a technical solution: a method for reducing the roughness of tunnel lining. By fully humidifying the lining concrete before coating construction and creating a local high-humidity curing environment using absorbent cotton cloth after coating construction, the construction quality of the roughness-reducing coating can be effectively controlled, solving problems such as surface shrinkage, pitting, and cracking of the coating.

[0027] Before applying the roughness-reducing coating, the inner surface of the tunnel lining concrete must first be treated to ensure that the tunnel lining concrete has been poured and reached the design strength grade. A high-pressure water gun or compressed air spray gun is used to thoroughly clean the inner surface of the lining, removing surface dust, oil, cement slurry, and other attachments. For any protruding concrete bulges or sharp edges, an angle grinder or chisel is used to smooth them, making the lining surface basically flat. After cleaning, the surface is rinsed again with high-pressure water to remove any remaining dust, and then allowed to air dry naturally until there are no obvious water marks on the surface.

[0028] As an optional implementation, after surface cleaning, a roughening treatment can be applied to enhance coating adhesion. Specifically, the operator holds a pointed hammer and evenly taps the surface of the lining concrete, creating a small pit with each tap. The depth of the pit is controlled between 1 and 3 mm, and the diameter is no more than 5 mm. The tapping force should be uniform to ensure the pits are evenly distributed across the lining surface. After the roughening treatment, compressed air is used to blow away any loose debris generated during tapping. Through this roughening treatment, a dense micro-textured structure is formed on the lining concrete surface, effectively increasing the contact area between the roughening coating and the concrete substrate, which is beneficial for improving the physical anchoring force and adhesion of the coating.

[0029] After surface cleaning and roughening, the pre-curing and humidification stage of the lining concrete begins. The purpose is to allow the concrete matrix to fully absorb water and reach a high moisture content saturation state. The specific operation is as follows: use spraying or watering equipment to continuously spray water on the inner surface of the lining. The water should evenly cover the entire lining surface to fully wet the surface but not to accumulate excessive water. Spray water no less than 3 times a day, in the morning, noon and afternoon respectively. The duration of each spraying is based on the complete wetting of the lining surface. The duration of pre-curing and humidification is determined according to the initial dryness of the lining concrete, generally 7 to 14 days.

[0030] During the pre-curing and humidification process, a large number of capillary pores inside the concrete continuously absorb water through capillary action, gradually reaching a saturated state. A portable concrete moisture content meter is used to select several representative measuring points on the lining surface for testing. When the moisture content at the measuring point is not less than 6%, the concrete is considered to have reached a sufficient degree of wetting.

[0031] After the pre-curing and humidification are completed, stop spraying water and let the lining surface stand for 2 to 4 hours to allow the free water on the surface to flow away under gravity or evaporate naturally in the air until there is no visible water or obvious water film on the lining surface. At this time, the inside of the concrete is fully wetted, but the surface is in a surface dry state. Excessive surface free water will not affect the adhesion and leveling of the roughness-reducing coating.

[0032] After the lining surface reaches a surface dry state, immediately apply the roughness-reducing coating. The roughness-reducing coating can be epoxy-based, polyurea-based, or fluorine-modified polymer-based. Depending on the coating type and application requirements, apply the coating evenly to the inner surface of the lining using brushing, rolling, or spraying. During the coating process, maintain a uniform coating thickness, controlling it within the design specifications; generally, the dry film thickness is 200–500 μm. During coating application, the ambient temperature should be controlled between 5℃ and 35℃. Avoid working under high temperatures, strong winds, or direct sunlight to prevent excessive evaporation of moisture from the coating surface.

[0033] After the roughness-reducing coating is applied, the curing stage begins immediately. A fully moistened absorbent cotton cloth is placed next to the coating to increase the humidity of the surrounding area through continuous evaporation of moisture. The cotton cloth should be a highly absorbent pure cotton fabric, such as cotton terry cloth or cotton non-woven fabric. The cloth should be 3–8 mm thick, 30–60 cm wide, and its length determined by the actual height of the tunnel. Before use, the cloth should be thoroughly soaked in clean water for at least 30 minutes to ensure the fibers fully absorb water. After soaking, remove the cloth and gently drain excess water until it is damp but not dripping.

[0034] The cotton cloth is installed vertically, with fasteners pre-installed on the tunnel lining surface. The fasteners can be supports that are mounted on the ground inside the tunnel. The cotton cloth is supported to ensure that the distance between adjacent pieces does not exceed 2m. The fully wetted cotton cloth is fixed on the supports to maintain appropriate tension in the vertical direction. A distance of 5-15cm is maintained between the cotton cloth and the coating surface. This ensures that the moisture evaporated from the cotton cloth can effectively diffuse to the vicinity of the coating surface, while avoiding direct contact between the cotton cloth and the coating surface, which could cause contamination or damage.

[0035] After the cotton cloth is set up, the coating is moisturized and cured. During the curing period, the moisture in the cotton cloth continues to evaporate into the surrounding air, which significantly increases the relative humidity of the air in the local space around the coating, maintaining it above 70%. In the high humidity environment, the rate of evaporation of moisture from the inside of the coating is greatly reduced, and the loss of moisture in the coating tends to be uniform. The shrinkage of the coating during the curing process is more consistent, thus effectively avoiding defects such as shrinkage lines, local pits and cracks caused by uneven water loss rates inside and outside.

[0036] During maintenance, the cotton cloth must be kept constantly moist. When signs of dryness appear on the surface, water should be added promptly. Watering can be done manually at regular intervals, with maintenance personnel checking the cloth's moisture level every 4-8 hours. For cloth showing signs of dryness, spray with water using a spray bottle or sprinkle with water using a hose until the cloth is moist again. Alternatively, an automatic watering system can be used to improve maintenance efficiency. A flexible watering hose is inserted along the length of the cotton cloth. The hose has several micro-holes with a diameter of 1-2 mm. One end of the hose is connected to a water supply source and equipped with a control valve, while the other end is closed. During maintenance, the water supply valve is opened every 6-12 hours for 5-15 minutes each time. Water permeates evenly into the cloth through the hose and micro-holes, achieving automatic and uniform watering without the need for manual sprinkling. This method is particularly suitable for maintenance work in long tunnels.

[0037] The curing period for the coating shall be no less than 7 days. During the curing period, the air temperature inside the tunnel should be controlled between 10℃ and 30℃. If the temperature inside the tunnel is too high, the frequency of water replenishment of the cotton cloth can be increased appropriately to maintain a higher air humidity. If the temperature is too low, the curing time can be extended appropriately to ensure that the coating is fully cured.

[0038] After the curing period, remove the support and the cotton cloth, and conduct a comprehensive inspection of the roughness reduction coating surface. A qualified coating surface should be smooth and flat, with uniform color, and free from defects such as shrinkage lines, pits, cracks, and peeling. The surface roughness should meet the roughness reduction requirements specified in the design. If any local defects are found, they should be repaired and the local curing should be carried out again after repair.

[0039] Example 1

[0040] During the surface treatment stage, a high-pressure water gun is used to thoroughly rinse the inner surface of the lining to remove surface dust and cement slurry. Then, an angle grinder equipped with a diamond grinding disc is used to grind and smooth the local protrusions on the surface. After that, a roughening treatment is carried out. The operator uses a pointed hammer to evenly tap the lining surface to form dense pits with a depth of about 2mm and a diameter of about 3mm, with a distribution density of about 300 pits per square meter. After tapping, the surface is blown with compressed air to remove loose debris.

[0041] During the pre-curing and humidification stage, a rotary spray nozzle was used to spray water onto the inner surface of the lining at a pressure of 0.3 MPa. Water was sprayed four times a day at 7:00, 11:00, 14:00, and 17:00, each time lasting 15 minutes, for 10 consecutive days. After 10 days, five measuring points were selected on the lining surface. A portable concrete moisture content meter was used to measure the moisture content at several representative points on the lining surface. When the moisture content at the measuring point was not lower than 7.5%, the concrete was considered to have reached a sufficient level of moisture. Water spraying was stopped, and the surface was left to stand for 3 hours. No visible water accumulation was observed on the lining surface.

[0042] During the roughness-reducing coating construction stage, epoxy-based roughness-reducing coatings were used. Components A and B were mixed evenly in a 1:1 ratio and then sprayed using a high-pressure airless sprayer at a pressure of 15 MPa. The distance between the spray gun and the lining surface was 30 cm. The spray gun was moved evenly to ensure uniform coating thickness, with the dry film thickness controlled at 300 ± 50 μm. The temperature inside the tunnel during construction was 22℃, and the relative humidity was approximately 55%.

[0043] During the coating curing stage, absorbent cotton cloths were immediately placed after spraying. These cloths were made of cotton terry cloth, 5mm thick, 50cm wide, and 3.5m long. The cloths were soaked in clean water for 40 minutes, then drained until no more dripping. The cloths were supported by a bracket, maintaining a 10cm gap between the cloths and the coating surface. The moisture level of the cloths was checked every 6 hours during curing. Cloths showing signs of drying were sprayed with clean water to replenish moisture. The temperature inside the tunnel was maintained at 20–25℃ during curing, and the evaporation from the cloths maintained a local relative humidity of 75–85%. The cloths were removed after 7 days of curing.

[0044] Ensure the coating surface is smooth and flat, with uniform color, and free from defects such as shrinkage lines, pits, and cracks.

[0045] Example 2

[0046] Construction of lining roughness reduction for old water conveyance tunnels that have been in operation for many years.

[0047] In the surface treatment stage, the lining surface is first thoroughly cleaned with a wire brush and a high-pressure water gun to remove attached scale, moss and loose particles. Locally eroded areas are repaired and leveled with epoxy mortar and cured for 3 days to achieve strength. After the repair is completed, the entire cross-section is roughened by using a pneumatic chisel to evenly roughen the lining surface, forming dense pits with a depth of about 2.5mm. After roughening, the surface is thoroughly blown away with compressed air.

[0048] During the pre-curing and humidification stage, since the old concrete is relatively dry, a low-pressure spray system is used to continuously spray water 5 times a day for 14 consecutive days. After 14 days, a concrete moisture content meter is used to select 10 measuring points on the lining surface for testing to ensure that the moisture content of each measuring point is between 6.5% and 7.5% to meet the construction requirements. Then, the water spraying is stopped, and the surface is left to stand for 4 hours. There is no visible water accumulation on the surface.

[0049] During the roughness reduction coating construction stage, polyurea-based roughness reduction coatings were used, and two-component spraying equipment was used for spraying. The dry film thickness of the coating was controlled at 400±50μm. The temperature inside the tunnel was 25℃ during construction, and the ventilation was good but there was no strong wind.

[0050] During the coating curing stage, an automatic water replenishment method was adopted. Cotton non-woven fabric, 6mm thick, 40cm wide, and 5.0m long, was used. A PVC hose was inserted inside the cotton fabric, with a 1.5mm diameter micro-hole for water outlet every 10cm along the hose wall. The cotton fabric was soaked in clean water for 50 minutes, then drained until no water dripped. The cotton fabric with the hose was vertically supported and fixed to the side of the coating, with an 8cm gap between the cotton fabric and the coating surface. The upper end of the hose was connected to a water supply branch pipe already installed in the tunnel, equipped with a solenoid valve. The solenoid valve was controlled by a timer, and during the curing period, it was set to open once every 8 hours for 10 minutes each time. Clean water was evenly seeped into the cotton fabric through the micro-holes of the hose, keeping the cotton fabric continuously moist. During the curing period, the temperature inside the tunnel was maintained between 18 and 28℃, and the local relative humidity was maintained above 80%. The cotton fabric was removed after 10 days of curing.

[0051] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the scope of the invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0052] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for roughening tunnel lining construction, characterized in that, Includes the following steps: Step 1: Clean the inner surface of the tunnel lining concrete to remove surface dust, oil stains and attachments, and level any local protrusions. Step 2: Roughen the surface of the cleaned lining concrete to form evenly distributed, densely packed micro-pits on the lining surface. Step 3: Pre-curing and humidifying the roughened lining concrete by continuously spraying water onto the inner surface of the lining using spraying or watering equipment to ensure that the concrete fully absorbs water and reaches saturation. Step 4: After the pre-curing and humidification are completed, stop spraying water and let it stand until the lining surface is dry and free of water accumulation. Step 5: Apply a roughness-reducing coating to the surface of the lining concrete after it has dried. Step Six: After the coating is applied, place a fully moistened absorbent cotton cloth next to the coating. The continuous evaporation of moisture from the cotton cloth will increase the humidity of the local space around the coating, thus moisturizing and maintaining the coating.

2. The method for roughening tunnel lining according to claim 1, characterized in that: The roughening treatment involves using a pointed hammer to evenly tap the surface of the lining concrete. The depth of the small pits formed by each tap is controlled to be 1-3 mm, and the diameter is no more than 5 mm. The pits are evenly distributed on the lining surface.

3. The method for roughening tunnel lining according to claim 1, characterized in that: In the pre-curing and humidification step, water is sprayed no less than 3 times a day, and the pre-curing and humidification lasts for 7 to 14 days.

4. The method for roughening tunnel lining according to claim 1, characterized in that: In the pre-curing and humidification step, when the moisture content of the measuring points on the lining surface is not less than 6%, the concrete is considered to have reached a sufficient degree of moisture.

5. The method for roughening tunnel lining according to claim 1, characterized in that: In step four, the settling time after stopping water spraying is 2 to 4 hours.

6. The method for roughening tunnel lining according to claim 1, characterized in that: The roughness-reducing coating is an epoxy-based roughness-reducing coating, a polyurea-based roughness-reducing coating, or a fluorine-modified polymer roughness-reducing protective coating, with a dry film thickness of 200–500 μm.

7. The method for roughening tunnel lining according to claim 1, characterized in that: The absorbent cotton cloth is made of pure cotton fabric with a thickness of 3-8mm and a width of 30-60cm. Before use, the cotton cloth should be soaked in clean water for at least 30 minutes until it is moist but not dripping.

8. The method for roughening tunnel lining according to claim 1, characterized in that: The absorbent cotton cloth is vertically positioned next to the coating by a support member, with a distance of 5 to 15 cm between the cotton cloth and the coating surface, and the distance between adjacent cotton cloths not exceeding 2 m.

9. The method for roughening tunnel lining according to claim 1, characterized in that: The moisturizing and maintenance period shall be no less than 7 days. During the maintenance period, the cotton cloth shall be kept moist at all times, so that the relative humidity of the air in the local space around the coating shall be maintained above 70%.

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