Underwater condition asphalt core wall dam core wall defect limited control grouting plugging method

Abstract

The invention discloses a limited control grouting plugging method for core wall defects of an asphalt core wall dam under the underwater condition. The method comprises the steps that S1, a viscous-plastic grouting slurry limited diffusion control method under the underwater condition is established; s2, establishing a quantitative control method for the grouting amount of the viscous-plastic grouting slurry under the underwater condition; and S3, wall front tire repairing type grouting and wall back drainage, seepage guiding and leaking stoppage are constructed. According to the underwater condition asphalt core wall dam core wall defect limited control grouting leaking stoppage method, quantitative analysis of the diffusion radius of the grouting slurry can be achieved, and secondary splitting of the asphalt core wall caused by too large slurry diffusion distance or invalid leaking stoppage caused by the fact that the slurry diffusion distance is too small and cannot be attached to the asphalt core wall is avoided; in addition, accurate control over the grouting amount is achieved, grout waste and underwater environment pollution caused by the too large grout amount or poor leaking stoppage effect caused by insufficient wrapping of the grout on asphalt core wall defect leaking stoppage due to the insufficient grout amount are avoided, and the method is suitable for asphalt core wall dam core wall defect leaking stoppage under various water depth conditions.

Description

Technical Field

[0001] The invention belongs to the technical field of water conservancy and hydropower engineering, and particularly relates to a method for limited controlled grouting and plugging core wall defects of an underwater asphalt core dam. Background Art

[0002] Asphalt concrete core dams offer advantages such as strong deformation adaptability, reliable anti-seepage effectiveness, strong seismic performance, and environmental friendliness. The dam structure can be divided from top to bottom into functional zones: the upstream rockfill shell, the upstream gravel transition layer, the asphalt concrete core, the anti-seepage downstream filter transition layer, and the downstream rockfill shell. The upstream transition layer and downstream filter layer, typically 1.5 to 3.0 meters thick, buffer the deformation difference between the core (low elastic modulus) and the shell material (high elastic modulus soil and rock), ensuring a smooth transition of overall dam deformation. A filter layer and drainage strip are located within the downstream dam to filter fine particles, direct seepage flow, and maintain dam foundation stability. The core anti-seepage body, located at the center of the dam, is connected to the bedrock and bank slope via a concrete pad. It bears the primary horizontal water pressure and exhibits high viscoelasticity and self-healing crack capacity, allowing it to adapt to dam settlement and temperature fluctuations. The use of asphalt concrete materials that can be obtained locally on site is not only pollution-free to water quality, but also has stable anti-seepage performance and excellent seismic performance. It is widely used in modern earth-rock dam projects.

[0003] However, in some areas, some asphalt concrete core dams built under complex dam construction conditions, such as deep overburden and steep river valleys, have experienced varying degrees of leakage. Because the core is extremely thin and conventional materials struggle to bond tightly to the asphalt concrete, direct repair is extremely difficult, and repairs are often carried out through controlled grouting of the upstream transition layer. Common methods for remediating leakage in asphalt core dams include: constructing concrete or geomembrane cutoff walls along both sides of the core to intercept seepage, grouting with valve pipes inside the dam body or at its interfaces, filling cracks with pulsating grouting, and injecting asphalt slurry in areas with severe leakage. The transition layer grouting method is particularly common: from the top of the dam crest, holes are drilled in layers and grouting is performed in rows in the upstream transition zone of the asphalt core, forming an underground grouting curtain to block seepage. In practice, several rows of grouting holes are generally set up along the dam axis in the upstream transition layer, and cementitious material slurry is injected into each row of holes in a designed sequence. Grouting sequences can be divided into shallow holes followed by deep holes. The grout type (e.g., paste slurry, mixed stabilized slurry, etc.) is determined for each hole segment based on factors such as water permeability. The slurry diffuses through the transition layer and eventually bonds with the core wall's anti-seepage material, forming a continuous, low-permeability, anti-seepage layer. By controlling the grouting sequence, pressure, and slurry type, transition layer grouting can effectively block potential leakage channels on both sides of the core wall and the dam foundation, thereby restoring the dam's anti-seepage performance without draining the reservoir.

[0004] However, the prior art has the following problems:

[0005] Grout diffusion is difficult to control: In traditional pressure-stabilized grouting, grout diffusion travels a long distance and is affected by multiple factors, making it difficult to accurately predict the actual grouting range and precisely calculate the required grouting volume. Excessive grouting can cause grout to overflow the intended area, impacting surrounding structures, while insufficient grouting can make it difficult to completely seal leaks. Excessive grouting pressure can also trigger hydraulic fracturing, damaging the asphalt core wall structure.

[0006] Guaranteed grouting effectiveness: Due to the lack of specialized design specifications and empirical guidance for asphalt core dam reinforcement, traditional reinforcement solutions rely heavily on empirically planned grouting, which often makes precise implementation difficult. In complex geological or underwater conditions, it's difficult to ensure the grout is strictly confined to the damaged area, reducing reinforcement efficiency and potentially causing secondary damage to the core wall.

[0007] Construction is difficult and risky: core dams generally cannot be emptied, and construction is restricted by the water environment. The viscoelastic properties of the core material and uneven dam settlement also introduce uncertainties into the construction process. These issues collectively restrict the effectiveness of traditional reinforcement measures.

[0008] The above shortcomings show that the existing technology is difficult to accurately control the diffusion of slurry, accurately predict the amount of slurry used, and avoid damage to the core wall when dealing with asphalt core wall dam leakage. It is urgent to propose a limited control grouting and plugging method for core wall defects of asphalt core wall dams under underwater conditions. Summary of the Invention

[0009] The present invention is proposed to solve the above-mentioned shortcomings, and its purpose is to provide a method for limited controlled grouting and plugging of core wall defects of asphalt core dams under underwater conditions. This method can achieve front-wall repair and plugging of asphalt core walls under underwater conditions through limited diffusion of visco-plastic grouting slurry and quantitative control of grouting amount.

[0010] In order to achieve the above purpose, the present invention adopts the following scheme:

[0011] A method for sealing core wall defects of an underwater asphalt core dam by limited controlled grouting comprises the following steps:

[0012] S1: Based on the visco-plastic characteristics of grouting materials, a slurry finite diffusion formula is established to determine the slurry diffusion distance R, as shown in the following formula:

[0013] (Formula 1); Where: K g is the permeability coefficient of the slurry in the transition material; △P is the grouting pressure gradient; α is the ratio of the slurry viscosity to the water viscosity; r w is the density of water; △n is the porosity gradient of the transition layer material; t is the grouting time; r0 is the drilling radius;

[0014] S2: Based on the finite diffusion formula of slurry, a quantitative control formula for grouting volume is established to determine the grouting volume Q, as shown in the following formula:

[0015] (Formula 2); Where t0 is the grouting time; C(t) is the function of slurry volume changing with time; R is the slurry diffusion distance; r0 is the borehole radius; α is the ratio of slurry viscosity to water viscosity; r w is the density of water; △n is the porosity gradient of the transition layer material; K g is the permeability coefficient of the slurry in the transition material; △P is the grouting pressure gradient;

[0016] S3: Using the determined slurry diffusion distance R and grouting volume Q, implement front-of-wall grouting to form a sealing body in front of the defective area of the asphalt core wall to seal the defective area; set a drainage pipe between the asphalt core wall and the corridor to drain the leaked water in the defective area of the core wall.

[0017] As a preferred embodiment, in step S1, when the calculated slurry diffusion distance R is less than the distance L from the center line of the borehole to the front of the asphalt core wall, the diffusion distance is adjusted by increasing the grouting pressure; when the calculated slurry diffusion distance R is greater than the distance L from the center line of the borehole to the front of the asphalt core wall, the diffusion distance is adjusted by reducing the grouting pressure.

[0018] As a preferred embodiment, in step S3, the sealing body formed by the pre-wall grouting is fitted with the defective area of the asphalt core wall.

[0019] As a preferred embodiment, in step S3, the drainage pipe is arranged at the lowest point between the asphalt core wall and the corridor.

[0020] As a preferred embodiment, in step S3, the grouting slurry is a high molecular polymer modified cement slurry.

[0021] As a preferred embodiment, in step S3, the drainage pipe is a PVC pipe or a steel pipe.

[0022] As a preferred embodiment, in step S3, the drainage pipe is installed by pre-buried method.

[0023] As a preferred embodiment, in step S3, the grouting time of the front-wall tyre-repair grouting is controlled within 1 to 4 hours.

[0024] As a preferred embodiment, in step S3, the grouting pressure of the front-wall tyre-repair grouting is in the range of 0.5 to 3.0 MPa.

[0025] As a preferred embodiment, in step S3, the grouting pressure of the front-wall tire-repair grouting is dynamically controlled by a real-time monitoring device.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] First, the limited diffusion control method of underwater visco-plastic grouting slurry constructed by the present invention can realize quantitative analysis of the diffusion radius of the grouting slurry, avoiding secondary splitting of the asphalt core wall due to excessive slurry diffusion distance, or ineffective plugging due to failure to achieve adhesion with the asphalt core wall due to excessive slurry diffusion distance.

[0028] Secondly, the present invention proposes a limited diffusion control model for viscoplastic slurry, which takes into account the yield characteristics of water medium and materials, providing a more accurate theoretical support for grouting design.

[0029] Third, the quantitative control method of the grouting amount of underwater visco-plastic grouting materials constructed by the present invention realizes the precise control of the grouting amount, avoiding the waste of slurry and underwater environmental pollution due to excessive slurry amount, or insufficient slurry amount leading to insufficient sealing of asphalt core wall defects, resulting in poor sealing effect.

[0030] Fourthly, the present invention creatively links the diffusion model with the grouting volume calculation, quantitatively predicts the required grouting volume, and realizes the predictability and controllability of grouting construction. Quantitative control optimizes the grouting filling degree of each partition, reduces blindness and waste, and improves leak plugging efficiency and safety.

[0031] Fifth, the present invention constructs a front-wall patching grouting and behind-wall drainage and seepage prevention method, which innovatively combines the front-wall patching grouting and behind-wall drainage and seepage prevention measures to construct a double-line defense plugging system, combining active repair with passive pressure relief to ensure that even a very small amount of residual leakage is effectively drained, significantly enhancing the reliability of the dam body's anti-seepage, reflecting a unique engineering management concept, and is suitable for plugging core wall defects of asphalt core dams under various water depth conditions.

[0032] Sixth, this invention deeply integrates grouting construction technology with dynamic monitoring and control, employing advanced sensing and control technologies to achieve real-time control of slurry diffusion. Through timely pressure adjustment and precise timing, combined with the use of high-performance slurry materials, the grouting effect is guaranteed to meet standards. This collaborative innovation model improves the consistency and controllability of construction quality, laying the foundation for successful leak plugging in complex underwater environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a flow chart of the method for limited controlled grouting and plugging of core wall defects of an underwater asphalt core dam according to the present invention. DETAILED DESCRIPTION

[0034] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0035] The method for limited controlled grouting and plugging of core wall defects of an underwater asphalt core dam according to the present invention comprises the following steps:

[0036] S1: Constructing a limited diffusion control method for visco-plastic grouting materials under underwater conditions

[0037] Based on the visco-plastic characteristics of grouting slurry, a finite diffusion formula for slurry is established, as shown in formula (1). The finite diffusion formula can be used to quantitatively analyze the diffusion radius of grouting slurry, avoiding secondary splitting of the asphalt core wall due to excessive slurry diffusion distance, or ineffective plugging due to the failure of slurry diffusion distance to adhere to the asphalt core wall. The permeability coefficient K of the specific engineering slurry in the transition material is obtained through physical tests, numerical simulations, etc. g , slurry viscosity to water viscosity ratio α, grouting pressure gradient △P, transition layer material porosity gradient △n, drilling radius r0 and other parameters. In this embodiment, the permeability coefficient K of the transition material is measured using a permeability tester. g A rotational viscometer is used to measure the ratio of slurry viscosity to water viscosity, α. ΔP is determined based on the grouting pressure selected by the on-site grouting system and the water pressure conditions of the dam body. The porosity gradient Δn of the transition layer material is determined by experimentally or empirically estimating the change in porosity of the transition material with depth. The drilling radius r0 is determined by the selected drill bit diameter (e.g., for a 110 mm diameter drill bit, r0 ≈ 55 mm). Substituting the above parameters into the slurry finite diffusion formula, the slurry diffusion distance R can be calculated. This embodiment uses the following relationship to express the finite diffusion model:

[0038] (Formula 1); Where: K g is the permeability coefficient of the slurry in the transition material; △P is the grouting pressure gradient; α is the ratio of the slurry viscosity to the water viscosity; r w is the density of water; △n is the porosity gradient of the transition layer material; t is the grouting time; r0 is the drilling radius.

[0039] Based on the above parameters, the slurry diffusion distance R is calculated and its compliance with the plugging requirements is determined. If it is less than the distance L between the borehole centerline and the front of the core wall, the slurry diffusion distance R can be increased by increasing parameters such as the grouting pressure. Otherwise, these parameters can be reduced. The process of slurry diffusion within the transition layer medium with a finite radius demonstrates that slurry diffusion exists within a controlled limit range. This limited slurry diffusion model allows for quantitative analysis and prediction of the slurry diffusion distance, preventing uncontrolled slurry diffusion. If the slurry diffusion distance is too large, the slurry may penetrate the core wall or cause secondary splitting and damage to the asphalt core wall. Conversely, if the slurry diffusion distance is too small, the slurry cannot reach and adhere to the core wall defects, resulting in ineffective plugging. The establishment of a limited diffusion model provides a precise theoretical basis for grouting construction, ensuring that the slurry diffusion range is controlled within the designed value.

[0040] In this embodiment, the calculated slurry diffusion distance R is compared with the distance L between the borehole centerline and the asphalt core wall defect location. If R is less than L (indicating that the slurry may not have reached the core wall defect), the grouting parameters need to be adjusted to increase the slurry diffusion range. Specific measures include: appropriately increasing the grouting pressure (gradually increasing it to the design upper limit within a safe range) to increase the pressure differential to promote further slurry penetration; extending the grouting time or selecting a grouting material with higher permeability to increase the R value. Conversely, if the calculated R is significantly greater than L (indicating that the slurry may have excessively diffused into the core wall, posing a risk of splitting), the grouting pressure should be reduced or the grouting time shortened to minimize the slurry diffusion distance and limit slurry diffusion to the area immediately in front of the core wall. Through this closed-loop control, construction personnel can control the actual slurry diffusion range near the target area, achieving limited diffusion. This ensures that the slurry adequately covers the core wall defect while preventing the adverse effects of excessive diffusion on the dam body. This step provides the necessary parameter foundation and safety margin for subsequent grouting volume control and actual grouting construction.

[0041] S2: Constructing a quantitative control method for grouting quantity of visco-plastic grouting materials under underwater conditions

[0042] On the basis of clarifying the slurry diffusion distance R, a quantitative control formula for the grouting volume is established based on the slurry finite diffusion formula, as shown in formula (2). The derivation of formula (2) comprehensively considers the volume filling characteristics during the slurry diffusion process: as the slurry diffuses in the porous medium, its filling range expands from the initial drilling radius r0 to the final slurry diffusion distance R, and the slurry volume that penetrates the medium pores increases with time. By combining the finite diffusion model with the relationship between the slurry flow rate and time, an expression for the accumulation of slurry volume over time can be obtained. The grouting volume control formula is expressed in integral form, that is, the grouting volume Q is calculated by accumulating the slurry volume change function C(t) over time within the grouting time t0. The quantitative control formula for the grouting volume Q can achieve precise control of the grouting volume Q, avoiding slurry waste and underwater environmental pollution caused by excessive slurry volume, or insufficient slurry volume resulting in insufficient slurry coverage of asphalt core wall defects and poor plugging effect.

[0043] (Formula 2); Where t0 is the grouting time; C(t) is the function of slurry volume changing with time; R is the slurry diffusion distance; r0 is the borehole radius; α is the ratio of slurry viscosity to water viscosity; r w is the density of water; △n is the porosity gradient of the transition layer material; K g is the permeability coefficient of the slurry in the transition material; △P is the grouting pressure gradient; among them, the slurry volume change function C(t) is obtained from the experiment, and the grouting volume is calculated to realize the quantitative calculation of the grouting material.

[0044] The function C(t) of the grouting volume change over time in the quantitative control formula can be obtained through the grouting test curve: a simulated grouting test is carried out under field or laboratory conditions, and the real-time flow rate or cumulative volume of the grouting injection process is recorded over time, so as to fit the C(t) function. For example, under common circumstances, C(t) will gradually decay over time, and can be fitted using an exponential function or an empirical formula. At the same time, the slurry diffusion distance R and related parameters obtained in step S1 are substituted into formula (2). The grouting volume Q required to complete the predetermined plugging can be obtained by analytical or numerical integration calculation. When calculating the grouting volume Q, a certain pore filling rate and slurry loss factor (corrected by △n) are taken into account to be close to the slurry utilization efficiency in actual engineering.

[0045] Grout volume control strategy. Based on the calculated grouting volume, the grouting process is precisely controlled during actual construction to ensure neither under-injection nor over-injection. To this end, the following measures can be taken: 1) Install a flow meter on the grouting equipment or measure the number of grout mixing buckets to monitor the injected grout volume in real time. 2) When the cumulative grouting volume approaches the designed value, slow the grouting rate and closely monitor pressure changes to prevent grout leakage or waste due to continued injection. 3) Once the designed grouting volume is reached, unless there are special circumstances (such as continued significant leakage), grouting should be stopped promptly to prevent excessive grout from gushing onto the dam surface or entering the reservoir water, potentially causing environmental pollution. If the grouting pressure significantly increases and stabilizes before the designed grouting volume is reached (indicating that the grouting area is full and grouting has ceased), grouting can be stopped prematurely to avoid safety hazards caused by overpressure. This quantitative control ensures that the injected grout is precisely the right amount: filling the pore spaces in front of the core wall defects, forming an effective seal, while also avoiding grout waste and environmental hazards. This precise control of grouting volume makes construction predictable and controllable, greatly improving the leak-proofing effect and construction economy.

[0046] S3: Constructing a front-wall grouting method and a back-wall drainage and seepage plugging method

[0047] Pre-wall grouting: Using the slurry diffusion distance R determined in step S1 and the grouting volume Q determined in step S2, pre-wall grouting is performed upstream of the asphalt core wall defect. Pre-wall grouting forms a slurry sealant layer in front of the core wall, similar to the principle of tire patching, much like applying a patch to the outside of a leaking hole, thereby blocking the leakage path. During construction, grouting holes are first arranged based on the location and extent of the core wall defect. Typically, a drill rig is used to drill downward along an incline at the dam crest or upstream slope, with the final hole positioned as close to the core wall defect front as possible (maintaining a distance of several meters from the core wall surface to avoid drilling directly through the core wall). During drilling, slurry wall protection or temporary casing is required to ensure the stability of the hole wall within the saturated gravel material. After drilling to the designed depth, a grouting stopper (hole sealer) is installed to seal the hole opening to prevent slurry backflow during grouting. The borehole radius r0 should be as consistent as possible with the value calculated in step S1. For example, a drill bit with a diameter of 100-130 mm (r0 ≈ 50-65 mm) is recommended. Next, connect a high-pressure grouting pump and grouting pipeline to inject the prepared slurry into the borehole. The grouting material is preferably a polymer-modified cement slurry. This slurry has a low initial viscosity for easy pumping, but gradually thickens and solidifies after injection. It possesses a certain degree of viscoelasticity and scour resistance, allowing it to adhere to the surface of the asphalt core wall underwater and harden into a consolidated mass. During the actual grouting process, injection should begin at a low pressure to displace accumulated water and air from the hole. Once the slurry passes through the perforations at the bottom of the borehole and enters the transition medium before the core wall, the pressure is gradually increased to the design pressure. For example, the pressure can be controlled within the range of 0.5 to 3.0 MPa, with the specific value selected based on the on-site soil impermeability and the core wall's pressure tolerance. Within this pressure range, low pressure facilitates slow slurry diffusion and avoids impacting the core wall, while high pressure overcomes penetration resistance at greater distances. Therefore, during construction, the pressure can be adjusted to dynamically control the slurry diffusion distance, ensuring that the slurry front advances to the core wall without penetrating. The grouting duration is controlled based on the grouting time t0 determined in step S2 and is generally between 1 and 4 hours. During this period, the grouting pressure is dynamically controlled using real-time monitoring equipment. Construction personnel should closely monitor the grouting pressure gauge and flow meter data, and record pressure-time and flow-time curves using the on-site real-time monitoring system. If the pressure suddenly rises to the upper limit or the slurry consumption reaches the designed grouting volume, the grouting should be terminated promptly. After grouting, the pressure can be maintained for an appropriate period (e.g., 10 to 30 minutes), after which the pressure can be relieved and the equipment removed. Through this process, the slurry diffuses and consolidates in the transition layer in front of the core wall, forming a seal that closely adheres to the defective area of the asphalt core wall. The thickness and range of the plugging body are controlled by the designed R and Q, which can completely cover the defect area and achieve positive plugging of the leakage channel.

[0048] Behind-the-wall drainage and seepage control measures: Considering the possibility of water leaking into the asphalt core wall through defects, this water often accumulates between the core wall and the downstream corridor (inspection corridor or drainage corridor), creating a "backwater pressure." To completely eliminate any remaining hidden dangers, the present invention combines pre-wall grouting with a behind-the-wall drainage and seepage control system. This involves adding a drainage channel downstream of the asphalt core wall (between the core wall and the corridor) to channel any remaining water. Preferably, a drainage pipe is embedded at the lowest point below the core wall defect, ensuring that any water that seeps into the core wall can flow directly into the pipe and drain away by gravity. This pipe can be made of PVC or galvanized steel, with a diameter typically ranging from 50 to 100 mm, depending on the expected seepage volume. During construction, drainage pipes can be buried near the downstream core wall using existing or pre-reserved holes within the corridor. For example, small holes can be drilled diagonally from the corridor toward the core wall, and drainage pipes can be inserted, with the pipe ends extending to a certain distance behind the core wall defects. A sump or pipe can then be installed on one side of the corridor to direct the diverted seepage water into the corridor drainage system. To prevent silt blockage, a filter screen or gravel filter layer can be installed at the drainage pipe inlet. The drainage pipe should be securely anchored and sealed within the dam body, and the gaps around the pipe should be backfilled with fine aggregate or grouting to prevent the formation of new leakage channels. This diversion and seepage design ensures that even if a small amount of water seeps through the core wall defects near the core wall sealing body, it will be quickly diverted away and prevented from accumulating within the dam body. This eliminates the threat of backwater pressure to the corridor and the downstream dam body, preventing damage to the corridor structure due to long-term water pressure erosion. This drainage measure and the aforementioned tire-patching grouting plugging together constitute a "double line of defense" leak-proof system: the former actively stops leakage, and the latter passively relieves pressure. The two complement each other and greatly improve the safety and reliability of the dam's anti-seepage.

[0049] Based on the proposed formula for limited slurry diffusion and quantitative grouting volume control, the present invention achieves limited diffusion pre-wall patching and sealing in front of core wall defects by controlling the slurry diffusion range and grouting volume. That is, the sealing body formed by the slurry fully fits and covers the core wall defect area. The sealing body formed by the pre-wall patching grouting fits the defect area of the asphalt core wall. At the same time, to address the permanent accumulation of water between the core wall and the corridor due to leakage, drainage pipes and other measures are used to ensure that the accumulated water is retained and drained, preventing damage to the corridor structure caused by the accumulated water. The drainage pipe is arranged at the lowest point between the asphalt core wall and the corridor. The grouting slurry is a polymer-modified cement slurry. The drainage pipe is a PVC pipe or a steel pipe. The drainage pipe is installed by pre-buried method. The grouting time is controlled within 1 to 4 hours. The grouting pressure ranges from 0.5 to 3.0 MPa. The grouting pressure is dynamically controlled by real-time monitoring equipment.

[0050] The present invention completes the implementation of the limited controlled grouting and plugging method for core wall defects of asphalt core wall dams under underwater conditions through the above steps. Through the organic combination of the above steps S1 to S3, the present invention successfully achieves effective plugging and repair of core wall defects of asphalt core wall dams under underwater conditions. The limited diffusion model and quantitative grouting control ensure that the slurry fills the area in front of the defect in a controlled manner and forms a stable sealing layer, while the combination of tire-filling grouting in front of the wall and drainage and seepage control behind the wall constructs an anti-seepage system that combines active sealing with passive drainage. In summary, this method has the advantages of strong technical pertinence and high construction operability. It can be widely used in the treatment of leakage defects of asphalt core wall dams under different water depths, and significantly improves the anti-seepage safety performance of the dam.

[0051] The above embodiments are merely illustrative of the technical solutions of the present invention. The present invention is not limited to the contents described in the above embodiments, but is subject to the scope defined by the claims. Any modifications, supplements, or equivalent substitutions made by those skilled in the art based on these embodiments are within the scope of protection claimed in the claims of the present invention.

Claims

1. A method for sealing core wall defects of an underwater asphalt core dam by limited controlled grouting, characterized by: The steps include: Based on the visco-plastic characteristics of grouting materials, a finite diffusion formula for slurry is established to determine the slurry diffusion distance R, as shown in the following formula: ； Where: K g is the permeability coefficient of the slurry in the transition material; △P is the grouting pressure gradient; α is the ratio of the slurry viscosity to the water viscosity; r w is the density of water; △n is the porosity gradient of the transition layer material; t is the grouting time; r0 is the drilling radius; Based on the finite diffusion formula of slurry, a quantitative control formula for grouting volume is established to determine the grouting volume Q, as shown in the following formula: ； Where t0 is the grouting time; C(t) is the function of slurry volume changing with time; R is the slurry diffusion distance; r0 is the borehole radius; α is the ratio of slurry viscosity to water viscosity; r w is the density of water; △n is the porosity gradient of the transition layer material; K g is the permeability coefficient of the slurry in the transition material; △P is the grouting pressure gradient; Using the determined slurry diffusion distance R and grouting volume Q, front-of-wall grouting is implemented to form a sealing body in front of the defective area of the asphalt core wall, thereby sealing the defective area; a drainage pipe is set between the asphalt core wall and the corridor to drain the leaked water in the defective area of the core wall.

2. The method for limited controlled grouting and plugging core wall defects of an underwater asphalt core dam according to claim 1, characterized in that: When the calculated slurry diffusion distance R is less than the distance L from the centerline of the borehole to the front of the asphalt core wall, the diffusion distance is adjusted by increasing the grouting pressure. When the calculated slurry diffusion distance R is greater than the distance L from the centerline of the borehole to the front of the asphalt core wall, the diffusion distance is adjusted by reducing the grouting pressure.

3. The method for limited controlled grouting and plugging core wall defects of an underwater asphalt core dam according to claim 1 is characterized by: The sealing body formed by the front-wall patching grouting fits the defective area of the asphalt core wall.

4. The method for limited controlled grouting and plugging core wall defects of an underwater asphalt core dam according to claim 1, 2 or 3, characterized in that: The drainage pipe is arranged at the lowest point between the asphalt core wall and the corridor.

5. The method for limited controlled grouting and plugging core wall defects of an underwater asphalt core dam according to claim 1, 2 or 3, characterized in that: The grouting material for the front-wall patching grouting is high-molecular polymer modified cement slurry.

6. The method for limited controlled grouting and plugging core wall defects of an underwater asphalt core dam according to claim 1, 2 or 3, characterized in that: The drainage pipe is a PVC pipe or a steel pipe.

7. The method for limited controlled grouting and plugging core wall defects of an underwater asphalt core dam according to claim 1, 2 or 3, characterized in that: The drainage pipe is installed in a pre-buried manner.

8. The method for limited controlled grouting and plugging core wall defects of an underwater asphalt core dam according to claim 1, 2 or 3, characterized in that: The grouting time of the front-wall patching grouting is controlled within 1 to 4 hours.

9. The method for limited controlled grouting and plugging core wall defects of an underwater asphalt core dam according to claim 8, characterized in that: The grouting pressure range of the front-wall patching grouting is 0.5~3.0MPa.

10. The method for limited controlled grouting and plugging core wall defects of an underwater asphalt core dam according to claim 9, characterized in that: The grouting pressure is dynamically controlled through real-time monitoring equipment.

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