Construction method of pressure grouting boundary curtain

Abstract

The application relates to a construction method of a pressure grouting boundary curtain, and belongs to the technical field of anti-seepage reinforcement of underground engineering. The method comprises the following steps: obtaining geological data of a preset grouting area; calculating a grouting hole arrangement scheme, a grouting sequence and initial grouting parameters based on the geological data; and performing drilling grouting in the preset grouting area according to the calculated grouting hole arrangement scheme, the grouting sequence and the initial grouting parameters. The method has the beneficial technical effects that: the construction method of the pressure grouting boundary curtain obtains the geological data of the preset grouting area in advance, and then matches the different grouting hole arrangement schemes, the grouting sequences and the initial grouting parameters according to different geological conditions of different areas, so that the problem of poor adaptability and unstable curtain quality caused by the traditional construction of one-size-fits-all is effectively solved, and the method is very suitable for the construction of complex karst strata, and can greatly improve the continuity and compactness of the curtain.

Description

Technical Field

[0001] This application relates to the field of underground engineering seepage prevention and reinforcement technology, and in particular to a construction method for a pressure grouting boundary curtain. Background Technology

[0002] Pressure grouting boundary curtain is a continuous and dense anti-seepage and reinforcement curtain formed by injecting grout into a pre-set underground area, which limits the diffusion range of the grout. It is widely used in water conservancy and hydropower, foundation pit engineering, mining and other fields.

[0003] Currently, the construction method of conventional pressure grouting boundary curtains mostly adopts the fixed parameter grouting and equal spacing hole layout mode, which has the problem of poor geological adaptability. The reason is that the traditional construction does not fully consider the differences in the micro-characteristics of the strata, such as the fissure aperture, the distribution of cavities, and the quality of the rock. It uses uniform grouting parameters (pressure, grout ratio). This method leads to incomplete filling of fissures and cavities, or excessive grouting, resulting in material waste and strata uplift and damage. Especially in complex karst strata, the continuity of the curtain is difficult to guarantee, and the curtain continuity and density are poor. Summary of the Invention

[0004] To address the problem of poor geological adaptability in existing pressure grouting boundary curtain construction methods, this application provides a construction method for pressure grouting boundary curtains.

[0005] In one aspect of this disclosure, a construction method for a pressure-grouting boundary curtain is proposed, comprising: Obtain geological data for the pre-defined grouting area; The grouting hole layout scheme, grouting sequence and initial grouting parameters are calculated based on geological data. Drilling and grouting are carried out in the preset grouting area according to the calculated grouting hole layout plan, grouting sequence and initial grouting parameters.

[0006] Preferably, the geological data includes: fracture-related data, rock mechanics-related data, karst cavity-related data, stratigraphic void-related data, and special geological distribution data; The fracture-related data include fracture orientation, fracture aperture, fracture roughness, fracture connectivity, fracture density, fracture orientation, and fracture permeability coefficient. The rock mechanics-related data include rock quality indicators, formation Poisson's ratio, rock integrity, formation uplift sensitivity, and rock saturated compressive strength. The data related to karst cavities include cavity diameter, cavity density, and cavity connectivity. The formation porosity-related data includes formation porosity development characteristics, porosity size, and formation porosity. The special geological distribution data includes the distribution range of karst cavities and the distribution range of areas with dense fissures.

[0007] Preferably, the calculation of the grouting hole layout scheme, grouting sequence, and initial grouting parameters based on geological data includes: Standardize the geological data; The comprehensive weight of the strata is calculated based on the standardized geological data, and it is determined whether the preset grouting area needs to be divided into several uniform areas. The grouting hole layout scheme is determined based on the comprehensive formation weight; Determining the pre-defined grouting area requires dividing it into several uniform zones, and determining the grouting sequence for each uniform zone based on standardized geological data. The initial grouting parameters are calculated based on the standardized geological data and the comprehensive weight of the strata. The initial grouting parameters include the initial grouting pressure, the initial grouting flow rate, and the grout mix ratio.

[0008] Preferably, the standardization process for the geological data includes: Through formula Transforming geological data into standardized data, among which Standardized data corresponding to a certain geological data. For a certain geological data, and These are the minimum and maximum reasonable values ​​for a certain geological data, respectively.

[0009] Preferably, the calculation of the stratigraphic composite weight based on the standardized geological data includes: Through formula Calculate the overall stratigraphic weights, where, Standardized data for fracture connectivity. Standardized data for fracture aperture. Standardized data for fracture density. Standardized data for cavity diameter. Standardized data for rock quality indicators.

[0010] Preferably, the grouting hole layout scheme based on the comprehensive formation weight includes: In response to W≥0.6, the grouting holes are arranged in a quincunx pattern; In response to 0.3≤W<0.6, the grouting holes are arranged in a rectangular pattern; In response to W < 0.3, the grouting holes are arranged in a rectangular pattern, and the spacing between the grouting holes in areas where the rock quality index is < 50% is smaller than the normal spacing. The normal hole spacing (1.2 + 0.3 W), = In the formula, Where is the slurry diffusion radius, K is the fracture permeability coefficient. t is the initial grouting pressure, e is the grouting time, and e is the crack aperture. Poisson's ratio of the strata, The slurry density is [not specified]. This refers to the initial setting time of the slurry.

[0011] Preferably, the grouting hole layout scheme based on the comprehensive formation weight further includes: The response depends on whether the cavity diameter d is ≥ 0.3m; In response to a cavity diameter d ≥ 0.3m, grouting holes are set up around the karst cavity in a ring-shaped distribution with a spacing smaller than the normal hole spacing.

[0012] Preferably, the grouting hole layout scheme based on the comprehensive formation weight includes: The depth of the grouting hole ) ,in To pre-set the curtain design depth, Standardized data for rock integrity.

[0013] Preferably, the step of determining whether the preset grouting area needs to be divided into several uniform areas based on the standardized geological data includes: Determine whether the geological data at various points within the pre-set grouting area are consistent; If inconsistencies are identified, areas with consistent geological data are grouped into a homogeneous region. If the results are consistent, then no division is necessary; The process of determining the preset grouting area requires dividing it into several uniform regions. The grouting sequence for each uniform region is determined based on standardized geological data, including: Through formula +0.2 +0.35 Calculate the grouting priority for each uniform region, where P is the grouting priority. Standardized data for sensitivity to formation uplift.

[0014] Preferably, the calculation of initial grouting parameters based on standardized geological data and stratigraphic weights includes: Through formula W Calculate the initial grouting pressure In the formula , Standardized data for the saturated compressive strength of rock; Through formula =25-18 Calculate the initial grouting flow rate , This is the initial grouting pressure; For crack aperture e ≤ 0.5 mm and void diameter d < 0.3 m, the grout mix ratio is: pure cement grout, water-to-solid ratio... ; For conditions where 0.5 mm < crack aperture e ≤ 1.0 mm or 0.3 m ≤ void diameter d < 1.0 m, the grout mix ratio is: a mixture of cement and fly ash, with a water-to-solid ratio of... fly ash content +10 ; In response to a crack aperture e > 1.0 mm or a cavity diameter d ≥ 1.0 m, the grout mix ratio is: composite grout, with a fixed ratio of water:cement:fly ash:bentonite = 1:0.75:0.25:0.08.

[0015] Beneficial technical effects: The construction method of the pressure grouting boundary curtain of this application obtains the geological data of the preset grouting area in advance, and then matches the grouting hole layout scheme, grouting sequence and initial grouting parameters according to the different geological conditions of different areas. It effectively solves the problems of poor adaptability and unstable curtain quality caused by the traditional "one-size-fits-all" construction method. It is very suitable for construction in complex karst strata and can greatly improve the continuity and density of the curtain. Detailed Implementation

[0016] In one aspect of this disclosure, a method for constructing a pressure grouting boundary curtain is provided, comprising: S1. Obtain geological data for the preset grouting area; S2. Calculate the grouting hole layout scheme, grouting sequence and initial grouting parameters based on geological data; S3. Drill and grout in the preset grouting area according to the calculated grouting hole layout plan, grouting sequence and initial grouting parameters.

[0017] Specifically, the geological data mentioned in S1 includes: fracture-related data, rock mechanics-related data, karst cavity-related data, stratigraphic void-related data, and special geological distribution data.

[0018] More specifically, the fracture-related data includes fracture orientation, fracture aperture, fracture roughness, fracture connectivity, fracture density, fracture orientation, and fracture permeability coefficient; The rock mechanics-related data include rock quality indicators, formation Poisson's ratio, rock integrity, formation uplift sensitivity, and rock saturated compressive strength. The data related to karst cavities include cavity diameter, cavity density, and cavity connectivity. The formation porosity-related data includes formation porosity development characteristics, porosity size, and formation porosity. The special geological distribution data includes the distribution range of karst cavities and the distribution range of areas with dense fissures.

[0019] In one embodiment, S1 obtains geological data of the preset grouting area by using borehole cameras combined with AI digital core technology to conduct a comprehensive survey of the preset grouting boundary area. The borehole camera equipment acquires a ring-shaped video inside the borehole, and computer vision technology is used to unfold, stitch, and restore the video to generate a virtual "digital core map". Then, a deep neural network model based on the TensorFlow framework is used to automatically identify the occurrence, width, roughness, and rock quality index (RQD value) of the formation fractures. At the same time, combined with micro-CT technology, the development characteristics and geometric parameters of the formation voids are analyzed to clarify the distribution range of special geological features such as karst cavities and fracture-dense areas, thereby obtaining the geological data of the preset grouting area.

[0020] Of course, before using borehole cameras combined with AI digital core technology to conduct a comprehensive survey of the pre-set grouting boundary area, it is necessary to level the working surface and set up construction barriers, drainage systems and safety protection facilities to ensure construction safety.

[0021] In this embodiment of the disclosure, S2 calculates the grouting hole layout scheme, grouting sequence, and initial grouting parameters based on geological data, including: S21. Standardize geological data; S22. Calculate the comprehensive weight of the strata based on the standardized geological data and determine whether the preset grouting area needs to be divided into several uniform areas; S23. Set the grouting hole layout scheme based on the comprehensive formation weight; S24. The pre-defined grouting area needs to be divided into several uniform areas. The grouting sequence of each uniform area is determined based on the standardized geological data. S25. Calculate the initial grouting parameters based on the standardized geological data and the comprehensive weight of the strata. The initial grouting parameters include the initial grouting pressure, the initial grouting flow rate, and the grout mix ratio.

[0022] In this embodiment of the disclosure, the purpose of standardizing the geological data in step S21 is to eliminate dimensional differences and improve the calculation accuracy of the grouting hole layout scheme, grouting sequence and initial grouting parameters.

[0023] In one embodiment, it can be achieved through the formula The geological data is standardized. In this formula, This refers to standardized data corresponding to a specific geological dataset, with values ​​ranging from 0 to 1. For a specific geological data, such as fracture-related data or rock mechanics-related data, and These are the minimum and maximum reasonable values ​​for a certain geological data. For example, the minimum reasonable value for fracture aperture is 0.1 mm, the maximum reasonable value for fracture aperture is 1 mm, the maximum reasonable value for cavity diameter is 5 meters, and the minimum reasonable value is 0.

[0024] In one embodiment, it can be achieved through the formula Calculate the comprehensive stratigraphic weight in S22, where, Standardized data for fracture connectivity. Standardized data for fracture aperture. Standardized data for fracture density. Standardized data for cavity diameter. These are standardized data for rock quality indicators. The coefficients preceding each standardized data point represent the weights of its geological data, for example... The weights for the connectivity of the fractures. The weights of rock quality indicators.

[0025] By assigning different weights to different geological data, the influence priority of different geological data is distinguished, enabling the calculated grouting hole layout scheme, grouting sequence, and initial grouting parameters to accurately adapt to the actual situation of the preset grouting area. Weight allocation allows W to accurately reflect the overall complexity of the strata, thereby adapting parameters such as hole layout and hole spacing to the current strata, avoiding the problems of poor adaptability and unstable curtain quality caused by the traditional one-size-fits-all approach.

[0026] In this embodiment of the disclosure, the step S22, which involves determining whether a pre-defined grouting area needs to be divided into several uniform areas based on standardized geological data, includes: S221. Determine whether the geological data at various points within the preset grouting area are consistent; S222. If inconsistencies are determined, areas with consistent geological data are divided into a uniform area; otherwise, if inconsistencies are determined, no division is necessary.

[0027] In this embodiment of the disclosure, the criterion for determining whether the geological data at various locations within the preset grouting area are consistent is based on the uniformity of the macroscopic and microscopic characteristics of the geological data, and it is determined whether the overall grouting area needs to be divided into multiple uniform areas.

[0028] Specifically, if the exploration results show that the core stratigraphic features such as fracture connectivity, fracture density, rock quality indicators, and cavity distribution within the pre-designed grouting area are uniform and consistent, and the fluctuation range of the standardized data of each feature is ≤0.1, then there is no need to divide it into multiple uniform areas, and the entire pre-designed grouting area is treated as a single uniform area.

[0029] Conversely, if the exploration results show that the core stratigraphic characteristics such as fracture connectivity, fracture density, rock quality indicators, and cavity distribution within the pre-designed grouting area are not uniform, and the fluctuation range of standardized data for each characteristic is >0.1, such as dense fractures in some areas, dense areas in others, or concentrated cavity groups in some local areas, then the overall grouting area needs to be divided into multiple uniform areas. Each uniform area has good uniform stratigraphic characteristics. This design can effectively ensure that the grouting hole layout scheme, grouting sequence, and initial grouting parameters can accurately adapt to the actual situation of the pre-designed grouting area, avoiding the problems of poor adaptability and unstable curtain quality caused by the traditional one-size-fits-all approach.

[0030] When it is determined that the preset grouting area needs to be divided into several uniform areas, the formula is used. +0.2 +0.35 Calculate the grouting priority for each uniform region, where P is the grouting priority. This is standardized data on formation uplift sensitivity; the larger the P-value, the higher the grouting priority.

[0031] In this embodiment of the disclosure, S23, the grouting hole layout scheme based on the comprehensive formation weight includes: S231, in response to W≥0.6, the grouting holes are arranged in a quincunx pattern; S232, In response to 0.3≤W<0.6, the grouting holes are arranged in a rectangular pattern; S233. In response to W < 0.3, the grouting holes are arranged in a rectangular pattern, and the spacing between the grouting holes in areas where the rock quality index is < 50% is smaller than the normal spacing. The normal hole spacing (1.2 + 0.3 W), = In the formula, Where is the slurry diffusion radius, K is the fracture permeability coefficient. t is the initial grouting pressure, e is the grouting time, and e is the crack aperture. Poisson's ratio of the strata, The slurry density is [not specified]. This refers to the initial setting time of the slurry.

[0032] Furthermore, the grouting hole layout scheme based on the comprehensive formation weight also includes: S234. Response to whether the cavity diameter d is ≥0.3m; S235. In response to a cavity diameter d ≥ 0.3m, grouting holes shall be set up around the karst cavity in a ring-shaped distribution with a spacing smaller than the normal hole spacing.

[0033] As can be seen, this embodiment fully considers the comprehensive weight of the strata and the various situations of the cavity diameter when setting the grouting hole layout scheme, and adopts targeted layout measures to effectively solve the problems of poor adaptability and unstable curtain quality caused by the traditional one-size-fits-all approach. For example, different W thresholds correspond to different strata types, and the W threshold is divided into multiple interval ranges. The resulting grouting hole layout scheme has extremely strong adaptability and is very close to the actual geological conditions.

[0034] In addition, it is specifically designed to supplement and densify grout in karst cavity areas, precisely addressing the problems of easy grout loss and incomplete filling in cavity areas, while taking into account the overall continuity of the pore layout and the seepage prevention needs of special geological areas.

[0035] Furthermore, different pore layouts are adopted for different strata. For example, a quincunx pattern is used in areas with dense fractures, while a rectangular pattern with local densification is used in dense areas. This ensures the pore density in areas with dense fractures and cavities, ensuring that the grout is filled densely, while avoiding the waste of materials and construction costs caused by excessive pore layout in dense areas.

[0036] In addition, the calculation of normal hole spacing and grout diffusion radius are accurately adapted to different strata characteristics. Compared with traditional calculation formulas, it can accurately reflect the infiltration and diffusion law of grout in fractures and cavities, which meets the needs of complex geological construction.

[0037] Furthermore, the grouting hole layout scheme based on the comprehensive formation weight includes: S236, Depth of the grouting hole ) ,in To pre-set the curtain design depth, Standardized data for rock integrity.

[0038] This hole depth calculation formula ensures that the grouting hole penetrates the bottom of the curtain, preventing groundwater from seeping in from the bottom, which meets the core requirements of seepage prevention. Moreover, by dynamically adjusting the rock integrity parameters, it avoids insufficient depth or excessive waste.

[0039] In this embodiment of the disclosure, S25, the calculation of the initial grouting parameters based on the standardized geological data and the comprehensive weight of the stratigraphy includes: S251, through formula W Calculate the initial grouting pressure In the formula , This is standardized data for the saturated compressive strength of rock. This formula combines a comprehensive weight W with the saturated compressive strength of rock. It accurately matches different geological conditions, avoiding excessive pressure that could cause strata uplift or insufficient slurry diffusion.

[0040] S252, through formula =25-18 Calculate the initial grouting flow rate , Initial grouting pressure; initial grouting flow rate It is directly related to the initial grouting pressure. The higher the pressure, the lower the flow rate, which conforms to the construction principle of "high pressure slow injection and low pressure fast injection" to ensure that the grout is filled densely and without waste.

[0041] S253. In response to a crack aperture e ≤ 0.5 mm and a cavity diameter d < 0.3 m, the grout mix ratio is: pure cement grout, water-to-solid ratio... ; S254. In response to conditions where 0.5mm < crack aperture e ≤ 1.0mm or 0.3m ≤ void diameter d < 1.0m, the grout mix ratio is: a mixture of cement and fly ash, with a water-to-solid ratio of... fly ash content +10 ; S255. In response to a crack aperture e > 1.0 mm or a cavity diameter d ≥ 1.0 m, the grout mix ratio is: composite grout, with a fixed ratio of water: cement: fly ash: bentonite = 1:0.75:0.25:0.08.

[0042] The grout mix is ​​classified according to the fissure aperture e and the cavity diameter d, and three types of grouts—pure cement, cement and fly ash, and composite grouts—are matched differently to accurately adapt to different geological scenarios (dense strata, fissured strata, karst cavity strata), ensuring curtain quality and good adaptability.

[0043] The construction method of the pressure grouting boundary curtain of this application obtains the geological data of the preset grouting area in advance, and then matches the grouting hole layout scheme, grouting sequence and initial grouting parameters according to the different geological conditions of different areas. It effectively solves the problems of poor adaptability and unstable curtain quality caused by the traditional "one-size-fits-all" construction method. It is very suitable for construction in complex karst strata and can greatly improve the continuity and density of the curtain.

[0044] Unless otherwise defined, the technical or scientific terms used in this application shall have the ordinary meaning understood by one of ordinary skill in the art to which this application pertains. The terms "first," "second," "third," and similar terms used in this application specification and claims do not indicate any order, quantity, or importance, but are merely used to distinguish different components. The terms "an" or "a" and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms "comprising" or "including" and similar terms mean that the elements or objects preceding "comprising" or "including" encompass the elements or objects listed following "comprising" or "including" and their equivalents, and do not exclude other elements or objects. "Above," "below," "left," "right," etc., are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0045] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A construction method for a pressure grouting boundary curtain, characterized in that... ,include: Obtain geological data for the pre-defined grouting area; The grouting hole layout scheme, grouting sequence and initial grouting parameters are calculated based on geological data. Drilling and grouting are carried out in the preset grouting area according to the calculated grouting hole layout plan, grouting sequence and initial grouting parameters.

2. The construction method of the pressure grouting boundary curtain according to claim 1, characterized in that: The geological data includes: fracture-related data, rock mechanics-related data, karst cavity-related data, stratigraphic void-related data, and special geological distribution data; The fracture-related data include fracture orientation, fracture aperture, fracture roughness, fracture connectivity, fracture density, fracture orientation, and fracture permeability coefficient. The rock mechanics-related data include rock quality indicators, formation Poisson's ratio, rock integrity, formation uplift sensitivity, and rock saturated compressive strength. The data related to karst cavities include cavity diameter, cavity density, and cavity connectivity. The formation porosity-related data includes formation porosity development characteristics, porosity size, and formation porosity. The special geological distribution data includes the distribution range of karst cavities and the distribution range of areas with dense fissures.

3. The construction method of the pressure grouting boundary curtain according to claim 1, characterized in that: The calculation of the grouting hole layout scheme, grouting sequence, and initial grouting parameters based on geological data includes: Standardize the geological data; The comprehensive weight of the strata is calculated based on the standardized geological data, and it is determined whether the preset grouting area needs to be divided into several uniform areas. The grouting hole layout scheme is determined based on the comprehensive formation weight; Determining the pre-defined grouting area requires dividing it into several uniform zones, and determining the grouting sequence for each uniform zone based on standardized geological data. The initial grouting parameters are calculated based on the standardized geological data and the comprehensive weight of the strata. The initial grouting parameters include the initial grouting pressure, the initial grouting flow rate, and the grout mix ratio.

4. The construction method of the pressure grouting boundary curtain according to claim 3, characterized in that: The standardization process for geological data includes: Through formula Transforming geological data into standardized data, among which Standardized data corresponding to a certain geological data. For a certain geological data, and These are the minimum and maximum reasonable values ​​for a certain geological data, respectively.

5. The construction method of the pressure grouting boundary curtain according to claim 3, characterized in that: The calculation of the stratigraphic composite weight based on standardized geological data includes: Through formula Calculate the overall stratigraphic weights, where, Standardized data for fracture connectivity. Standardized data for fracture aperture. Standardized data for fracture density. Standardized data for cavity diameter. Standardized data for rock quality indicators.

6. The construction method of the pressure grouting boundary curtain according to claim 5, characterized in that: The grouting hole layout scheme based on the comprehensive formation weight includes: In response to W≥0.6, the grouting holes are arranged in a quincunx pattern; In response to 0.3≤W<0.6, the grouting holes are arranged in a rectangular pattern; In response to W < 0.3, the grouting holes are arranged in a rectangular pattern, and the spacing between the grouting holes in areas where the rock quality index is < 50% is smaller than the normal spacing. The normal hole spacing (1.2 + 0.3 W), = In the formula, Where is the slurry diffusion radius, K is the fracture permeability coefficient. t is the initial grouting pressure, e is the grouting time, and e is the crack aperture. Poisson's ratio of the strata, The slurry density is [not specified]. This refers to the initial setting time of the slurry.

7. The construction method of the pressure grouting boundary curtain according to claim 6, characterized in that, The grouting hole layout scheme based on the comprehensive formation weight also includes: The response depends on whether the cavity diameter d is ≥ 0.3m; In response to a cavity diameter d ≥ 0.3m, grouting holes are set up around the karst cavity in a ring-shaped distribution with a spacing smaller than the normal hole spacing.

8. The construction method of the pressure grouting boundary curtain according to claim 3, characterized in that, The grouting hole layout scheme based on the comprehensive formation weight includes: The depth of the grouting hole ) ,in To pre-set the curtain design depth, Standardized data for rock integrity.

9. The construction method of the pressure grouting boundary curtain according to claim 5, characterized in that: The determination of whether the preset grouting area needs to be divided into several uniform areas based on standardized geological data includes: Determine whether the geological data at various points within the pre-set grouting area are consistent; If inconsistencies are identified, areas with consistent geological data are grouped into a homogeneous region. If the results are consistent, then no division is necessary; The process of determining the preset grouting area requires dividing it into several uniform regions. The grouting sequence for each uniform region is determined based on standardized geological data, including: Through formula +0.2 +0.35 Calculate the grouting priority for each uniform region, where P is the grouting priority. Standardized data for sensitivity to formation uplift.

10. The construction method of the pressure grouting boundary curtain according to claim 5, characterized in that: The calculation of initial grouting parameters based on standardized geological data and stratigraphic weights includes: Through formula W Calculate the initial grouting pressure In the formula , Standardized data for the saturated compressive strength of rock; Through formula =25-18 Calculate the initial grouting flow rate , This is the initial grouting pressure; For crack aperture e ≤ 0.5 mm and void diameter d < 0.3 m, the grout mix ratio is: pure cement grout, water-to-solid ratio... ; For conditions where 0.5 mm < crack aperture e ≤ 1.0 mm or 0.3 m ≤ void diameter d < 1.0 m, the grout mix ratio is: a mixture of cement and fly ash, with a water-to-solid ratio of... fly ash content +10 ; In response to a crack aperture e > 1.0 mm or a cavity diameter d ≥ 1.0 m, the grout mix ratio is: composite grout, with a fixed ratio of water:cement:fly ash:bentonite = 1:0.75:0.25:0.08.

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