Slurry proportion regulation and control method for slurry balance shield in composite stratum

Abstract

The invention relates to a method for regulating and controlling the slurry ratio of a slurry shield in a composite stratum, which comprises the following steps of: parameter acquisition: acquiring stratum information parameters of a construction section through a method of exploration geophysical prospecting and drilling coring, setting a plurality of slurry parameter monitoring points at a construction site, and monitoring to obtain slurry parameters; and slurry proportion design regulation and control before construction and slurry proportion regulation and control in the construction process are carried out, and the slurry proportion is regulated and controlled by combining real-time shield tunneling in the process through obtained stratum information parameters and slurry parameters. The mud system suitable for the composite stratum is designed according to different stratum geological conditions and monitored and adjusted at any time; by obtaining the stratum information parameters, the mud proportion is adjusted and controlled through the effective pressure conversion rate and the relation between the stratum information parameters and the mud parameters, and the effective pressure conversion rate is further improved in combination with the shield parameters; in the whole shield construction process, the mapping relation between slurry and shield parameters is optimized in real time, the slurry proportion is adjusted, the slurry film forming speed and density are improved, and the drilling efficiency is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of tunnel construction and relates to a method for regulating and controlling mud proportion of a composite stratum mud-water balance shield. Background Art

[0002] Shield construction has become the preferred construction method for the construction of transportation infrastructure and water conservancy projects in my country. Compared with earth pressure balance shields, slurry shields are more commonly used in complex geological conditions such as large sections and crossing water bodies. Slurry shields are currently the preferred construction equipment for tunnel projects crossing rivers. They integrate excavation, support, and slag removal, greatly improving the efficiency of tunnel construction. With the continuous increase in transportation demand, slurry shields, as the preferred equipment for crossing rivers and straits, will usher in a period of rapid development. However, the geological conditions in slurry shield construction are complex, which puts higher requirements on shield mud. In the actual construction process, due to changes in formation conditions and shield parameters, the mud parameters cannot adapt to the new shield construction conditions, resulting in a decrease in the shield construction speed. Therefore, it is of great practical significance to develop a mud ratio control method suitable for the site.

[0003] The Chinese invention with application number CN202310258819.7 has applied for a method for determining the type of mud film of a mud-water shield in sandy formations. Based on the obtained formation soil samples and mud material samples, indicators are used to quantify the state of the mud film. This method is only for sandy formations and not for complex formations. After obtaining the state of the mud film, the method does not regulate the mud according to the state of the mud film to increase the quality of the film. Summary of the invention

[0004] In view of the problems of the prior art, the present invention provides a method for regulating the mud ratio of a composite stratum mud-water balance shield, which is used to regulate the mud ratio before construction and during shield operation to improve the shield construction efficiency.

[0005] The present invention is achieved through the following technical solutions:

[0006] A method for controlling the ratio of slurry in a composite stratum mud-water balance shield, wherein the slurry components include bentonite, soda ash, water and additives, and the additives include a viscosity enhancer and a fluid loss reducer; the method specifically includes the following steps:

[0007] S1, parameter acquisition;

[0008] Before construction, the formation information parameters of the construction area are obtained through geophysical survey and core drilling methods; at the same time, multiple mud parameter monitoring points are set up at the construction site to monitor and obtain mud parameters;

[0009] The formation information parameters include: formation hydrostatic pressure, excess pore water pressure, permeability, compression modulus, internal friction angle and cohesion. Among them, the formation hydrostatic pressure represents the pressure exerted by groundwater on the formation, and the unit is Pascal (Pa). The magnitude of the formation hydrostatic pressure depends on the depth of the groundwater and the density of the water. Excess pore water pressure refers to the water pressure difference in the pore water pressure at a certain point in the saturated soil that exceeds the hydrostatic pressure, and the unit is Pascal (Pa).

[0010] Mud parameters include: mud density, filtration loss, and mud pressure.

[0011] S2. Design and control of mud ratio before construction;

[0012] In the early stage of construction, the mud ratio is adjusted by the obtained formation information parameters and mud parameters; the method of adjusting the mud ratio is: according to the relationship between the effective pressure conversion rate and the formation information parameters and mud parameters, the mud ratio is designed and adjusted to improve the effective pressure conversion rate;

[0013] The characterization relationship between effective pressure conversion rate, formation information parameters and mud parameters is as follows:

[0014]

[0015] Among them, ξ s is the effective pressure conversion rate, P s is the mud pressure, P w is the formation hydrostatic pressure, P e is the excess pore water pressure.

[0016] In slurry shield construction, the density of the mud film reflects whether the mud parameters are suitable, while the effective pressure conversion rate reflects the relationship between the time of mud film formation and the density of the mud film. Specifically, the time required for the effective pressure conversion rate to no longer increase or to increase slowly from the initial value is the mud film formation time. The earlier the mud film is formed, the denser the mud film is, and the effective pressure conversion rate ξ s The higher.

[0017] In the early stage of construction, the mud ratio is determined by adjusting the relationship between formation information parameters, mud parameters and effective pressure conversion rate; the purpose of adjusting the mud ratio is to optimize the mud parameters to match the characteristics of the construction formation, thereby improving the effective pressure conversion rate s Through precise control, the formation speed of the mud film can be accelerated, the density of the mud film can be improved, and the safety and efficiency of the construction can be ensured.

[0018] S3. Mud ratio control during construction;

[0019] During the construction, as the shield construction progresses, multiple mud parameter monitoring points are added on site to monitor the mud parameters. According to the characterization relationship between the effective pressure conversion rate and the formation information parameters and mud parameters (1), combined with the real-time shield construction composite formation and shield parameters, the mud ratio is adjusted to improve the effective pressure conversion rate.

[0020] The mud parameter monitoring points of the present invention are respectively set in the mud water bin and the inner wall of the tunnel; wherein the monitoring point in the mud water bin monitors the mud density and viscosity in the mud water bin in real time; the monitoring point on the inner wall of the tunnel monitors the penetration of the mud into the tunnel wall, the pressure size and distribution. wherein the mud density is automatically measured by the differential pressure density meter and the gamma ray density meter set at the monitoring point to monitor the mud density in real time.

[0021] The composite stratum described in the present invention includes a mixed layer of two or more of conglomerate, quartz sandstone, argillaceous sandstone, sandy shale, limestone and granite. The composite stratum is not a single stratum, and its stratum changes are continuous and irregular.

[0022] Furthermore, the present invention adjusts the mud according to the characterization relationship (1) among formation information parameters, mud parameters and effective pressure conversion rate, thereby increasing the mud loss while ensuring the stability of mud density and mud viscosity parameters; the loss is controlled to be below 15 mL in high permeability formations such as conglomerate and quartz sandstone, below 20 mL in medium permeability formations such as muddy sandstone and sandy shale, and below 25 mL in low permeability formations such as limestone and granite.

[0023] The increase of mud filtration loss will reduce the density of mud film, and then reduce the effective pressure conversion rate. The mud formula design in the early stage of construction should consider reducing the mud filtration loss.

[0024] Furthermore, in the present invention, in mud regulation according to the characterization relationship (1) among formation information parameters, mud parameters and effective pressure conversion rate, the mud density sets a mud safety density window, and the mud density is limited within the safety density window.

[0025] The safe density window of mud before construction is set as: 1.05-1.3 kg / m 3 , quartz sandstone 1.2~1.4kg / m 3 , argillaceous sandstone 1.05~1.3kg / m 3 , sandy shale 1.05~1.3kg / m 3 , limestone 1.2~1.4kg / m 3 , granite 1.2~1.4kg / m 3 .

[0026] Increasing mud pressure can increase the effective pressure conversion rate, but the mud pressure cannot be too high. Excessive mud pressure will cause mud to invade the formation, causing problems such as surface uplift, affecting construction progress and safety. A mud safety density window needs to be set in the early stage of construction. The mud safety density window refers to the mud density that needs to be maintained within a reasonable range during drilling or shield construction to ensure the stability of the wellbore or tunnel wall and construction safety. This range is the mud safety density window. The determination of this window is based on geomechanical parameters such as the collapse pressure, fracture pressure and pore pressure of the formation. When the mud pressure is less than the fracture pressure of the formation, it is increased as much as possible to improve the effective pressure conversion rate and ensure that a dense mud film is formed faster in the early stage of construction.

[0027] In S3 of the present invention, the mud ratio is adjusted and controlled in combination with the real-time shield construction composite stratum and shield parameters to improve the effective pressure conversion rate; wherein the shield parameters include the shield cutter head rotation speed, the number of cutters, the number of cutters on the same track and the excavation speed; the specific method is: based on the mud parameters obtained by monitoring, the influence law between the mud parameters and the shield parameters is established, and the effective pressure conversion rate is combined with the characterization relationship (1) of the formation information parameters and the mud parameters to adjust the mud ratio, improve the effective pressure conversion rate, and finally improve the drilling efficiency.

[0028] Among them, the cutter disc speed: conglomerate 1.0~1.1rpm, quartz sandstone 1.1~1.2rpm, mudstone 1.0~1.1rpm, sandy shale 1.0~1.1rpm, limestone 1.1~1.2rpm, granite 1.1~1.3rpm; excavation speed: conglomerate 15~25mm / min, quartz sandstone 5~15mm / min, mudstone 15~25mm / min, sandy shale 15~25mm / min, limestone 5~10mm / min, granite 3~5mm / min.

[0029] The influence of the mud parameters on the effective pressure conversion rate is as follows: an increase in the mud filtration loss will lead to a decrease in the effective pressure conversion rate, while a decrease in the mud filtration loss will lead to an increase in the effective pressure conversion rate.

[0030] When adjusting the mud ratio during the construction, the mud loss is increased as much as possible while ensuring the stability of parameters such as mud density and viscosity. The increase in the loss can be achieved by adding a viscosity enhancer such as CMC.

[0031] The specific gravity of mud and water in the construction process of the present invention is 1.05-1.30 g / cm 3 The lower limit is 1.05g / cm 3 The upper limit is determined according to the special requirements of the construction. When the shield passes through the upper soft and lower hard sections, 1.20g / cm 3 . For formations with strong slurry-making ability, 1.1 g / cm3 The full-section hard rock section can even select 1.4g / cm according to the monitoring results. 3 .

[0032] The viscosity of the mud described in the present invention is maintained in the range of 20 to 35 seconds.

[0033] From the perspective of the suspension requirements of soil particles and the matching of the mud water treatment system, the gel strength (static shear force) of the mud water is required to be moderate; from the perspective of fluidity, the kinematic viscosity should not be too high. Considering the self-slurrying ability of the mud water treatment system, as the number of rings in the clay layer increases, the mud becomes thicker and thicker, and the specific gravity also rises linearly, and its corresponding funnel viscosity will also increase. However, when constructing in sandy soil, the mud viscosity will decrease. The range of the mud viscosity of the present invention is selected to be maintained at 20 to 35 seconds.

[0034] The benefits of the present invention:

[0035] The method for regulating the mud ratio of a slurry shield in composite strata of the present invention designs a set of mud systems suitable for composite strata according to different geological conditions of complex strata and monitors and adjusts them at any time. During the construction process, the mud ratio is dynamically regulated by the shield parameters obtained in the process of the slurry shield drilling into different strata, so that the mud film is formed faster and denser, the drilling speed is increased, and the drilling efficiency is improved.

[0036] The present invention obtains formation information parameters, uses the relationship between effective pressure conversion rate and formation information parameters and mud parameters to adjust and control the mud ratio, and further combines shield parameters to improve the effective pressure conversion rate. The formation information parameters obtained by the present invention include formation hydrostatic pressure, excess pore water pressure, permeability, compression modulus, internal friction angle and cohesion; the mud ratio is ultimately reflected in the mud parameters, and the mud parameters mainly include density, viscosity, filtration loss, lubricity and mud pressure; the shield parameters mainly include cutter head speed, number of cutters, number of cutters on the same track and propulsion speed.

[0037] The present invention uses the effective pressure conversion rate to characterize the film-forming speed and density of the mud film. The higher the effective conversion rate, the faster the mud film-forming speed and the denser the mud film.

[0038] The method of the present invention adjusts the mud ratio and increases the effective pressure conversion rate through the relationship between the formation and the mud parameters in the early stage of construction, so as to form a dense mud film quickly and improve the drilling speed in the early stage of construction.

[0039] During construction, the present invention adjusts the mud ratio and improves the effective pressure conversion rate through the influence of shield parameters on mud parameters and the relationship between mud parameters and effective pressure conversion rate, so that the mud film remains dense during shield construction and the drilling speed is improved.

[0040] The present invention optimizes the mapping relationship between mud and shield parameters in real time during the entire process of shield construction to adjust the mud ratio, ultimately achieving improved effective pressure conversion rate, increased mud film formation speed and density, and improved drilling efficiency. DETAILED DESCRIPTION

[0041] The present invention is further described below in conjunction with specific implementation methods. The specific implementation methods are further descriptions of the principles of the present invention and do not limit the present invention in any way. Technologies that are the same or similar to the present invention do not exceed the scope of protection of the present invention.

[0042] To elaborate on the implementation mode of the control method of the present invention, the control method is described in detail below:

[0043] S1 parameter acquisition: formation analysis and preliminary design of mud formula. First, according to the geological exploration data, the formation information parameters are obtained, and the formation at the shield construction site is analyzed in detail. The formation information parameters include but are not limited to key parameters such as formation hydrostatic pressure Pw, excess pore water pressure Pe, permeability coefficient, compression modulus, internal friction angle and cohesion.

[0044] S2 Pre-construction mud ratio design and control: Based on the parameters obtained in S1, a suitable mud formula is preliminarily designed. Generally speaking, the shield mud formula mainly includes bentonite, thickener, fluid loss reducer, soda ash and water, and corresponding additives are added according to the specific characteristics of the formation, such as thickener CMC (carboxymethyl cellulose), fluid loss reducer (xanthan gum), etc.

[0045] During the preliminary design, the effective pressure conversion rate of the mud is s .

[0046] According to the representation relation

[0047] Among them, P s The mud pressure is increased by increasing the mud density, but it should be noted that increasing the mud pressure can increase the effective pressure conversion rate, but the mud pressure must be within the safe pressure window. Excessive mud pressure will cause formation rupture, mud intrusion into the formation will cause surface uplift and other problems, affecting the construction progress and safety. Too low mud pressure will cause formation collapse. In the early stage of construction, a mud density needs to be set so that the mud pressure is less than the formation rupture pressure, and it is increased as much as possible to improve the effective pressure conversion rate and ensure that a dense mud film is formed faster in the early stage of construction. And reduce the mud loss to improve the density of the mud film.

[0048] S3: Real-time monitoring and adjustment of mud ratio during shield construction. During shield construction, real-time monitoring of various parameters of mud, such as density, viscosity, filtration loss, etc. At the same time, record various parameters of the shield machine, such as cutter head speed, number of cutters, number of cutters on the same track, and advancement speed.

[0049] According to the real-time monitoring of mud parameters and shield parameters, drilling into different strata will lead to changes in shield parameters. Combined with the correlation between mud parameters and shield parameters established in the early stage, analyze whether the current mud ratio is suitable for the current construction conditions. If not, the mud ratio needs to be adjusted in time. When adjusting, the key indicators such as the physical and chemical stability, fluidity and filtration loss of the mud should be comprehensively considered to improve the pressure conversion rate of the mud to ensure that the mud can effectively balance the water and soil pressure of the excavation surface and ensure the smooth progress of the shield construction.

[0050] The mud ratio is dynamically regulated and optimized. The details are as follows:

[0051] 1. Set up multiple mud ratio monitoring points: Set up monitoring points in the shield machine mud tank and the inner wall of the tunnel to monitor the mud parameters in real time. By comparing the mud parameters at different locations, understand the changes in the mud during the circulation process.

[0052] 2. Analyze the changing trend of mud parameters: According to the mud analysis results at the monitoring points, analyze the changing trend of mud pressure conversion rate as shield construction progresses. If the mud pressure conversion rate deviates from the normal range, the mud ratio needs to be adjusted in time.

[0053] 3. Optimize the mud formula: Since the change of the formation leads to the change of shield parameters, which affects the mud performance, the mud formula should be optimized and adjusted. During optimization, you can try to change the proportion of bentonite, CMC, soda ash and other components, or add additives to change the pressure, viscosity and filtration loss of the mud, so as to improve the pressure conversion rate of the mud.

[0054] 4. Verify the optimization effect: Apply the optimized mud formula to actual construction and observe the shield construction effect. If the effect is good, continue to use the formula; if the effect is not good, further adjustment and optimization are required.

[0055] In order to ensure the effectiveness of mud ratio control, it is necessary to evaluate and provide feedback on the mud film quality. The specific methods are as follows:

[0056] 1. Mud film quality assessment: The mud film quality is assessed by coring, observing the excavation face, etc. The assessment indicators include the thickness, uniformity, and density of the mud film. If the mud film quality is poor, the mud ratio needs to be further adjusted.

[0057] 2. Feedback adjustment results: Feedback the mud film quality assessment results to the mud ratio control system, and fine-tune the mud ratio based on the feedback results. Through continuous iterative optimization, the mud ratio can be more adapted to the current formation conditions.

[0058] Take a railway super-large diameter slurry shield project as an example. The main line length of the railway is 10.009 km. The civil engineering of the bid section mainly includes a shield tunnel of 7716.5 m, an open-cut tunnel of 1353 m, and two working shafts. The following is a detailed introduction to the application process of the present invention:

[0059] Before construction, the formation characteristics are analyzed according to the geological exploration data, and the mud formula is preliminarily designed. In this case, the formation characteristics are interbedded mud sandstone and limestone, and the formation information parameters include: hydrostatic pressure Pw is 2MPa, excess pore water pressure Pe is 0.5MPa. The preliminarily designed mud formula is 10% bentonite, 0.2% CMC, 0.5% soda ash and water balance.

[0060] During the construction process, the mud parameters and shield parameters were monitored in real time. Due to the change of the stratum during the shield construction, the shield parameters (cutter head speed and propulsion speed) changed, and it was found that the mud density gradually increased with the construction.

[0061] According to the real-time monitoring results and the correlation rules established in the early stage, the current mud ratio is analyzed to see whether it is appropriate. In this case, it is found that the large amount of mud loss during the construction process leads to a decrease in the mud pressure conversion rate, which affects the mud-water conveying capacity, and the mud density gradually increases, with a tendency to break through the mud density safety window. Therefore, it is decided to adjust the mud formula, reduce the proportion of bentonite to 8%, and add an appropriate amount of fluid loss reducer.

[0062] The optimized mud formula was applied to actual construction and the construction effect was observed. It was found that the fluidity of the mud was significantly improved after adjustment, and the quality of the mud film was also improved. Therefore, it was decided to continue to use the optimized mud formula for subsequent construction.

[0063] During the subsequent construction process, the mud parameters and shield parameters will continue to be monitored in real time, and the mud formula will be fine-tuned according to the actual situation. Through continuous iterative optimization, the mud ratio will always adapt to the current formation conditions to ensure the smooth progress of shield construction.

[0064] Through the implementation of the present invention, dynamic regulation and optimization of the slurry ratio of the composite stratum mud-water balance shield can be achieved, and the mud film quality and shield construction efficiency can be improved. At the same time, the present invention also has certain flexibility and scalability, and can be adaptively adjusted according to different stratum conditions and construction requirements.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. Although the present invention has been described in detail with reference to the above embodiments, it should be understood by those skilled in the art that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for regulating the ratio of mud-water balance shield in composite formation, wherein the mud composition comprises bentonite, soda ash, water and additives, and the additives comprise a viscosity enhancer and a fluid loss reducer; characterized in that The process includes the following: S1, parameter acquisition; Before construction, the formation information parameters of the construction area are obtained through geophysical survey and core drilling methods; at the same time, multiple mud parameter monitoring points are set up at the construction site to monitor and obtain mud parameters; Formation information parameters include: formation hydrostatic pressure, excess pore water pressure, permeability, compression modulus, internal friction angle, and cohesion; Mud parameters include: mud density, filtration loss, and mud pressure; S2. Design and control of mud ratio before construction; In the early stage of construction, the mud ratio is adjusted by the obtained formation information parameters and mud parameters; the method of adjusting the mud ratio is: according to the relationship between the effective pressure conversion rate and the formation information parameters and mud parameters, the mud ratio is designed and adjusted to improve the effective pressure conversion rate; The characterization relationship between effective pressure conversion rate, formation information parameters and mud parameters is as follows: Among them, ξ s is the effective pressure conversion rate, P s is the mud pressure, P w is the formation hydrostatic pressure, P e is the excess pore water pressure; S3. Mud ratio control during construction; During the construction, as the shield construction progresses, multiple mud parameter monitoring points are added on site to monitor the mud parameters. According to the characterization relationship between the effective pressure conversion rate and the formation information parameters and mud parameters (1), combined with the real-time shield construction composite formation and shield parameters, the mud ratio is adjusted to improve the effective pressure conversion rate.

2. The method for controlling the ratio of slurry for composite stratum mud-water balance shield according to claim 1, characterized in that: The mud parameter monitoring points are set in the mud and water bin and on the inner wall of the tunnel respectively; among them, the monitoring point in the mud and water bin monitors the density and viscosity of the mud in the mud and water bin in real time; the monitoring point on the inner wall of the tunnel monitors the penetration of the mud into the tunnel wall, the pressure size and distribution.

3. The method for controlling the slurry ratio of composite stratum mud-water balance shield according to claim 2, characterized in that: Composite strata include mixed layers of two or more of the following: conglomerate, quartz sandstone, mudstone, sandy shale, limestone, and granite.

4. The method for controlling the ratio of slurry for composite stratum mud-water balance shield according to claim 3 is characterized by: In mud adjustment according to the characterization relationship (1) among formation information parameters, mud parameters and effective pressure conversion rate, the mud loss is increased while ensuring the stability of mud density and mud viscosity parameters; the loss is controlled below 15 mL in high permeability conglomerate and quartz sandstone formations, below 20 mL in medium permeability mudstone and sandy shale formations, and below 25 mL in low permeability limestone and granite formations.

5. The method for controlling the slurry ratio of composite stratum mud-water balance shield according to claim 3 is characterized by: In the mud adjustment according to the characterization relationship (1) among formation information parameters, mud parameters and effective pressure conversion rate, the mud density sets a mud safety density window, and the mud density is limited within the safety density window.

6. The method for controlling the slurry ratio of composite stratum mud-water balance shield according to claim 5 is characterized by: The safe density window of mud before construction is set as: 1.05-1.3 kg / m 3 , quartz sandstone 1.2~1.4kg / m 3 , argillaceous sandstone 1.05~1.3kg / m 3 , sandy shale 1.05~1.3kg / m 3 , limestone 1.2~1.4kg / m 3 , granite 1.2~1.4kg / m 3 .

7. The method for controlling the slurry ratio of a composite stratum mud-water balance shield according to claim 3 is characterized by: In the S3, the mud ratio is adjusted and controlled in combination with the real-time shield construction composite stratum and shield parameters to improve the effective pressure conversion rate; wherein the shield parameters include the shield cutter head rotation speed, the number of cutters, the number of cutters on the same track and the excavation speed; the specific method is: based on the mud parameters obtained by monitoring, the influence law between the mud parameters and the shield parameters is established, and the effective pressure conversion rate is combined with the characterization relationship (1) of the formation information parameters and the mud parameters to adjust the mud ratio, improve the effective pressure conversion rate, and finally improve the drilling efficiency.

8. The method for controlling the slurry ratio of a composite stratum mud-water balance shield according to claim 7, characterized in that: Cutter disc speed: 1.0~1.1rpm for conglomerate, 1.1~1.2rpm for quartz sandstone, 1.0~1.1rpm for mudstone, 1.0~1.1rpm for sandy shale, 1.1~1.2rpm for limestone, and 1.1~1.3rpm for granite; Excavation speed: 15~25mm / min for conglomerate, 5~15mm / min for quartz sandstone, 15~25mm / min for mudstone, 15~25mm / min for sandy shale, 5~10mm / min for limestone, and 3~5mm / min for granite.

9. The method for controlling the slurry ratio of composite stratum mud-water balance shield according to claim 8, characterized in that: The specific gravity of mud and water during construction is 1.05~1.30g / cm 3 .

10. The method for controlling the slurry ratio of composite stratum mud-water balance shield according to claim 8, characterized in that: During the construction process, the viscosity of the mud is maintained at 20 to 35 seconds.

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