CN110837695A - Method for evaluating average permeability of surrounding rock of broken granite tunnel - Google Patents
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Abstract
The invention relates to the technical field of permeability evaluation, in particular to an evaluation method for the average permeability of surrounding rocks of a broken granite roadway, which comprises the following specific steps: s1: firstly, a reversal rule of the air seepage direction of surrounding rocks of the roadway in summer and winter is revealed through long-time monitoring and analysis; s2: then, based on Darcy law, deducing a roadway surrounding rock average permeability evaluation model; s3: finally, a pressurization test is adopted, a method for determining the gas seepage critical inflation pressure of the surrounding rock of the roadway is provided, and a set of evaluation technology suitable for the average permeability of the surrounding rock of the underground roadway with the complex structure is formed. According to the invention, a broken granite roadway is taken as a research object, and a roadway ventilation test is adopted to explore the broken surrounding rock average permeability evaluation method based on the Darcy law. Firstly, a reversal rule of the air seepage direction of surrounding rocks of the roadway in summer and winter is revealed through long-time monitoring and analysis; and then, deriving an average permeability evaluation model of the surrounding rock of the roadway based on Darcy law.
Description
Technical Field
The invention relates to the technical field of permeability assessment, in particular to a broken granite roadway surrounding rock average permeability assessment method.
Background
Radon is a natural decay product of uranium in the crust, and uranium is abundant in the crust, widely distributed and extremely dispersed, and can be found in almost all kinds of rocks. Radon is harmful gas with radioactivity, and when the concentration of radon in the environment is higher than a certain level, the radon can generate harm to people in different degrees, and along with the continuous development of the wide application of underground engineering and the continuous deepening of understanding of the harm of radon by people, the research on the radon precipitation rule and the radon reduction method in the underground engineering is more and more concerned.
Disclosure of Invention
The invention aims to provide a method for evaluating the average permeability of surrounding rocks of a broken granite roadway, so as to solve the problems in the background technology.
In order to achieve the purpose, the invention provides the following technical scheme:
a broken granite roadway surrounding rock average permeability evaluation method comprises the following specific steps:
s1: firstly, a reversal rule of the air seepage direction of surrounding rocks of the roadway in summer and winter is revealed through long-time monitoring and analysis;
s2: then, based on Darcy law, deducing a roadway surrounding rock average permeability evaluation model;
s3: finally, a pressurization test is adopted, a method for determining the gas seepage critical inflation pressure of the surrounding rock of the roadway is provided, and a set of evaluation technology suitable for the average permeability of the surrounding rock of the underground roadway with the complex structure is formed.
As a further scheme of the invention: the specific operation steps in the step S1 are as follows:
the method comprises the following steps: arranging an air door at a position 100m away from a roadway opening in the roadway to serve as a measuring section of natural ventilation;
step two: the shape and size of the ventilation sectional area of the air door are controlled by adjusting the number of the spliced door plates on the retaining wall;
step three: 3 measuring points are distributed on the measuring section, an electronic breeze meter is adopted to measure the wind speed, temperature monitoring points are arranged at the positions 20m away from the roadway opening on the inner side and the outer side of the roadway, a multi-parameter meteorological sensor is adopted to measure the temperature, and the measured wind speed data and the measured temperature data are recorded.
As a still further scheme of the invention: the radon concentration in summer is 7.5 multiplied by 104Bq/m3The radon concentration in winter is lower than 300Bq/m3The concentration of radon in spring and autumn is between that in winter and summer.
As a still further scheme of the invention: the specific operation steps in the step S2 are as follows:
the method comprises the following steps: processing the mountain body where the roadway is located into a uniform porous medium;
step two: and deducing a surrounding rock average permeability calculation model by adopting Darcy's law.
As a still further scheme of the invention: the specific operation steps in the step S3 are as follows:
the method comprises the following steps: a sealing door is arranged at the mouth of the experimental underground roadway, and a ventilation measuring section is arranged at a position 150 meters away from the mouth of the underground roadway;
step two: closing a closed door of a tunnel junction of the underground tunnel, then opening fans in two fan rooms, carrying out press-in ventilation on the underground tunnel, and adjusting inflation pressure in the underground tunnel by changing the opening of the door;
step three: respectively measuring ventilation data when a closed door of the underground tunnel junction is opened and closed, and simultaneously monitoring and recording radon concentration at a wind speed measurement section;
step four: and calculating whether the fluid seepage obeys Darcy law according to the seepage Reynolds number.
As a still further scheme of the invention: and measuring three groups of data in each state by using the ventilation and radon concentration data measured in the third step, and averaging the results.
As a still further scheme of the invention: the critical Reynolds number in seepage in the step four is 0.2-0.3.
Compared with the prior art, the invention has the beneficial effects that: the method for evaluating the average permeability of the broken surrounding rock based on the Darcy law is explored by taking a broken granite roadway as a research object and adopting a roadway ventilation test. Firstly, a reversal rule of the air seepage direction of surrounding rocks of the roadway in summer and winter is revealed through long-time monitoring and analysis; then, based on Darcy law, deducing a roadway surrounding rock average permeability evaluation model; finally, a pressurization test is adopted, a method for determining the gas seepage critical inflation pressure of the surrounding rock of the roadway is provided, and a set of evaluation technology suitable for the average permeability of the surrounding rock of the underground roadway with the complex structure is formed. Effectively avoids the defect that the permeability of the rock mass is lack of macroscopicity in the traditional laboratory rock sample matching method and the in-situ drilling water injection/gas method, and has wide application value and guiding significance.
Drawings
FIG. 1 is a schematic diagram of a natural ventilation seasonal variation rule in an underground tunnel of a broken granite tunnel surrounding rock average permeability evaluation method.
FIG. 2 is a layout diagram of ventilation rectification cross sections and measuring points of an underground tunnel in the method for evaluating the average permeability of surrounding rocks of a broken granite tunnel.
FIG. 3 is a graph showing a relationship between natural ventilation volume of an underground tunnel in summer and internal and external temperature differences in an evaluation method for average permeability of surrounding rocks of a broken granite tunnel.
FIG. 4 is a graph showing a relation between natural ventilation volume of an underground tunnel in winter and internal and external temperature difference in an evaluation method of average permeability of surrounding rocks of a broken granite tunnel.
FIG. 5 is a layout diagram of an experimental underground roadway in a broken granite roadway surrounding rock average permeability evaluation method.
FIG. 6 is a schematic diagram of section wind speed measurement distribution points in a broken granite roadway surrounding rock average permeability evaluation method.
FIG. 7 is a graph of radon concentration in an underground roadway before and after a sealing door is closed in the method for evaluating the average permeability of surrounding rocks of a broken granite roadway.
FIG. 8 is a comparison table of air volume changes before and after closing of a sealing door in the broken granite roadway surrounding rock average permeability evaluation method.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1 to 6, in an embodiment of the present invention, an evaluation method for average permeability of surrounding rock of a broken granite roadway includes the following specific steps:
s1: firstly, a reversal rule of the air seepage direction of surrounding rocks of the roadway in summer and winter is revealed through long-time monitoring and analysis;
s2: then, based on Darcy law, deducing a roadway surrounding rock average permeability evaluation model;
s3: finally, a pressurization test is adopted, a method for determining the gas seepage critical inflation pressure of the surrounding rock of the roadway is provided, and a set of evaluation technology suitable for the average permeability of the surrounding rock of the underground roadway with the complex structure is formed.
The specific operation steps in the step S1 are as follows:
the method comprises the following steps: arranging an air door at a position 100m away from a roadway opening in the roadway to serve as a measuring section of natural ventilation;
step two: the shape and size of the ventilation sectional area of the air door are controlled by adjusting the number of the spliced door plates on the retaining wall;
step three: as shown in fig. 2, 3 measuring points are arranged on the measuring section, an electronic breeze instrument is adopted to measure the wind speed (the model of the electronic breeze instrument is EY3-2A, the manufacturer of the electronic breeze instrument is Beijing Huaxing century instrument Co., Ltd.), air temperature monitoring points are arranged at the positions 20m away from the roadway crossing on the inner side and the outer side of the roadway, a multi-parameter meteorological sensor is adopted to measure the air temperature (the model of the multi-parameter meteorological sensor is HCD1019-5P, the manufacturer of the multi-parameter meteorological sensor is Chengdu city Shijun science Co., Ltd.), and the measured wind speed data and the measured air temperature data are recorded.
Depending on the project that the roadway is deeply buried in the granite body, the radon concentration change in the roadway also has obvious seasonal regularity: the radon concentration in summer is 7.5 multiplied by 104Bq/m3The radon concentration in winter is lower than 300Bq/m3The concentration of radon in spring and autumn is between that in winter and summer. Long-term observation shows that natural ventilation exists in the roadway all the year round under the condition of no mechanical ventilation, the wind direction change also has obvious seasonal characteristics, and the phenomenon of upper and lower layering and reverse is caused. The situation of natural ventilation in the roadway in summer and winter is qualitatively described as shown in fig. 1: in summer, the wind direction is inward along the underground roadway above a neutralization interface (namely an imaginary interface with zero natural wind speed, wherein the wind direction begins to reverse), and the wind direction is outward below the neutralization interface; the opposite is true in winter. Because the underground roadway is provided with only oneAnd if the seepage of gas in the surrounding rock is not considered, the mass conservation law is considered, and the air flowing into (out of) the upper part of the roadway is supplemented by the reverse airflow at the lower part to achieve balance. To achieve the balance, even if the ventilation section area of the underground roadway is reduced, the phenomenon of upper and lower layering reversal inevitably exists, and the neutralization interface is located in the middle position of the ventilation section, but the actual situation is not. Experiments show that when the ventilation section is reduced to a certain degree, the natural wind direction is changed into a single direction, and the natural wind direction is outward along the roadway in summer and inward in winter, which shows that the natural wind in the roadway in summer can continuously flow outward from the whole view; in winter, the phenomenon that air flows from the outside to the inside of the roadway also continuously exists. Obviously, the air flowing out in summer needs to be supplemented by the air flowing in, and the air flowing in winter needs to flow out, so that the natural pressure balance can be achieved, which shows that the air can seep in the mountain under the natural pressure: in summer, the water flows into the roadway from the mountain body, and in winter, the water flows into the mountain body from the roadway.
As shown in fig. 3 and 4, when the wind cross section is 13cm, the natural wind is a unidirectional wind. In summer, the natural ventilation volume in the roadway is linearly related to the temperature difference between the inside and the outside of the roadway, and the larger the temperature difference between the inside and the outside of the roadway is, the larger the natural ventilation volume is; in winter, the temperature of the outside air of the roadway is lower, and compared with summer, the temperature difference between the inside and the outside of the roadway can be larger, and the natural ventilation quantity is also larger. Therefore, an obvious linear relation exists between the temperature difference between the inside and the outside of the roadway and the natural ventilation quantity. Because the change of the inside and outside difference in temperature of tunnel directly influences the change of pressure differential, so can think: the larger the pressure difference between the inside and the outside of the roadway is, the larger the natural ventilation volume in the roadway is, namely the larger the seepage intensity of the gas in the mountain is. Analyzing that the phenomenon of air seepage exists in the surrounding rock of the visible roadway, the phenomenon of seasonal reversal exists in the seepage direction, the seepage strength and the temperature difference inside and outside the roadway are in a linear correlation relationship, so that the seasonal difference of the radon concentration in the roadway is explained to a certain extent, and continuous natural airflow flows out of the roadway in summer, comes from the surrounding rock, carries a large amount of radon, and causes the radon concentration in the underground roadway to be higher; the natural airflow exists in winter, but the direction is opposite to summer, namely the natural airflow flows into the underground roadway from the outside, the gas flowing into the underground roadway seeps to the outside of a mountain body through cracks in the surrounding rocks, and in the process, fresh air outside continuously carries radon into the surrounding rocks and is discharged to the outside of the mountain body, so that the radon concentration in the underground roadway is kept at a lower level.
The specific operation steps in the step S2 are as follows:
the method comprises the following steps: processing the mountain body where the roadway is located into a uniform porous medium;
step two: and deducing a surrounding rock average permeability calculation model by adopting Darcy's law.
The general granite rock mass belongs to a fractured rock mass, and the fractured rock mass seepage field is not generally treated by an isotropic porous medium in an equivalent way when being researched. The fracture is not existed or the unfixed fracture is distributed irregularly or loose substances are formed, all the fractures are filled and consolidated by fine particles, and the permeability similar to that of rock mass is caused, so that the fracture can be regarded as isotropic porous medium seepage. According to geological survey data of a researched roadway, the surface of a mountain body where the roadway is located is seriously weathered, cracks develop, more broken zones exist, granular fillers are filled in the cracks, and surrounding rocks are broken more through subsequent various explosion experiments in the roadway. Therefore, the mountain body where the roadway is located is treated into a uniform porous medium, meanwhile, the linear correlation relation between the air seepage intensity and the temperature difference is considered, and a surrounding rock average permeability calculation model is derived by adopting Darcy's law. According to Darcy's law, the seepage velocity is proportional to the pressure gradient, i.e., for the same porous medium, different pressure gradients correspond to different seepage velocities. If the pressure gradient within the porous medium and the corresponding percolation velocity can be measured, the permeability of the porous medium can be determined, making the following assumptions to ensure the applicability of Darcy's Law:
(1) the gas in the experimental process conforms to an ideal gas state equation;
(2) the experimental process is considered according to the isothermal process, the density of the gas is only related to the pressure, and the kinetic viscosity coefficient is constant;
(3) neglecting the action of gravity;
(4) the gas flow is considered according to laminar flow, namely the seepage in the medium conforms to Darcy's law;
(5) the surrounding rock is treated into a uniform porous medium.
In steady state conditions, the one-dimensional darcy seepage satisfies the mass conservation equation:
in the formula: ρ is the gas density and can be expressed by the ideal gas equation of state: p ═ ρ RT;
v is Darcy's seepage velocity, formula:
when the permeability k of the rock mass is constant, equation (1) can be expressed as:
it is converted into an equation under a one-dimensional cylindrical coordinate system:
the following results were obtained:
experiment-based equivalent radius gamma of underground roadwayinAnd when the underground roadway with the uneven section segmentation is regarded as a large circular hole with the same diameter in the calculation process, the underground roadway with the uneven section segmentation is regarded as a large circular hole with the same diameter
rin＝A/2πL0Wherein A is the inner surface area of the underground roadway after considering the underground roadway overbreak (average linear overbreak amount is 300mm), m2，L0Is the total effective length of the shaft line of the underground tunnel, m.
When the gas pressure field in the rock mass is stable, the gas pressure in the underground tunnel is P1(ii) a At a distance r from the center point of the underground roadwayoutWhere the pressure is assumed to be the initial pressure P in the rock mass0Then the corresponding boundary conditions are:
the following can be found:
can correspondingly calculate C2In radial flow of a pore medium, the pressure gradient of the gas is not constant, i.e. the gas flow rate is not constant.
In a section of radius r, where the mass flow (kg/s) of the gas flowing through is equal, the ideal gas equation of state has:
pQ＝pscQsc＝const (8)
gas volume flow rate on a section with radius r of 2 pi rL0v wherein L0The length of the seepage flow cylindrical surface is the effective length of the experimental underground roadway. Then there is
The formula (4) or (7) is brought into the formula (9) as
Combining the formulas (8) and (10), and calculating the permeability of the surrounding rock by the formula
In the formula: k is the average permeability of the surrounding rock of the underground roadway, m2；
PSCTaking 1.01 × 10 as standard atmospheric pressure value5Pa；
QSCIs qiVolume standard volume flow, converted from equation of state, m3/s；
Mu is the motion viscosity coefficient of air, 1.8X 10-5Pa·s；
routThe radius of an effective range (defining the distance from the center of an underground roadway to a radon concentration balance point in a rock mass) of an experiment is m, considering that the migration of gas in a fractured rock mass is mainly controlled by seepage and diffusion;
p0the pressure in the underground roadway before inflation is Pa;
P1the value of the pressure in the underground roadway in the stable inflation state is the critical inflation pressure (determined according to the following experiment) Pa.
The formula (11) is a permeability calculation formula used in the experiment. According to the formula, the parameter which determines the greatest difficulty is the critical inflation pressure p1And radius of experimental effective range routWherein r isoutValues can be obtained according to numerical simulation and literature (taking 7-10 m), and p is determined through experiments below1The value of (a).
The specific operation steps in the step S3 are as follows:
the method comprises the following steps: a sealing door is arranged at the mouth of the experimental underground roadway, and a ventilation measuring section is arranged at a position 150 meters away from the mouth of the underground roadway;
step two: closing a closed door of a tunnel junction of the underground tunnel, then opening fans in two fan rooms, carrying out press-in ventilation on the underground tunnel, and adjusting inflation pressure in the underground tunnel by changing the opening of the door;
step three: respectively measuring ventilation data when a closed door of an underground roadway opening is opened and closed, simultaneously monitoring and recording radon concentration at a wind speed measurement section, respectively measuring three groups of data in each state of the measured ventilation and radon concentration data, and averaging the results;
step four: calculating whether the fluid seepage obeys Darcy's law according to the seepage Reynolds number, wherein the critical Reynolds number in the seepage is 0.2-0.3.
The ventilation system is used for carrying out micro-positive pressure inflation on the closed underground tunnel in the rock mass, and gas can seep into the surrounding rock mass from the underground tunnelAfter a sufficiently long time, the gas pressure field in the rock mass stabilizes. The aeration quantity in the underground tunnel is measurable, when the gas pressure field in the rock mass is stable, the air pressure in the underground tunnel is also stable, and the air pressure value can be obtained through measurement. According to the two data, the permeability of the rock mass can be obtained by using a calculation formula based on Darcy's law, or the average permeability of the rock mass assumes that the gas seepage generated in the experimental process conforms to the Darcy's law. The experiment is carried out in summer, and according to the sensitivity of the radon concentration to airflow exchange, when the radon concentration in the underground roadway of the experiment reaches the winter level, the gas in the rock mass is considered to have seepage in the same direction as that in winter. If the underground roadway is considered as a hole extending into the interior of a large mountain, when the hole is inflated and a certain positive pressure is formed, a part of the gas will be discharged through the channels in the mountain in a seepage manner. And in the pressurization process, the condition of air flow exchange between the underground roadway and the surrounding rock can be judged according to the change of radon concentration in the underground roadway. Experiments show that the radon concentration in the underground tunnel can be maintained at the winter level (about 300 Bq/m) after the inflation pressure reaches 200Pa3) I.e. critical inflation pressure p1200Pa is taken. Because the design margin of the wind pressure of the ventilator in the underground roadway is more than 500Pa, the resistance formed by the ventilation and pressurization experiment on the underground roadway can be considered not to influence the wind quantity sent into the underground roadway by the ventilator. The wind speed measurement result is shown in table 1, after the sealing door of the underground roadway opening is closed, the air volume of the ventilation system is reduced by 12.5 percent, and the wind speed measurement result can be considered as follows: the air quantity of the system loss is the air quantity which escapes to the atmosphere after flowing through the mountain in a seepage way, and the air quantity is the air quantity difference (1.13 m) before and after the closing door of the underground roadway opening is closed3In s). From this, Q in the equation (11) can be determined from the ideal gas state equationSCCalculated, QSC＝0.96m3/s。
As shown in FIG. 7, after the sealing door is closed for 2 hours, the radon concentration in the underground roadway is 7.5 multiplied by 10 from the average value4Bq/m3 rapidly decreased to 300Bq/m3Left and right and keep stable, and reach the level of the natural state in winter. Since radon concentration is very sensitive to air flow exchange, the radon concentration drops rapidlyThe low indicates that the exchange direction of the airflow between the underground roadway and the surrounding rock changes. By combining the seasonal change rule of radon concentration, the seepage direction of gas in the mountain is reversed, namely after the closed door is closed, the gas in the underground roadway enters the mountain under the driving of the pressure of 200Pa through the seepage effect. From this, p in the formula (11) can be determined1＝200+p0. According to the formula (11) and the parameters determined by experiments, the average permeability of the surrounding rock of the experimental underground roadway can be obtained by calculation: k is 1.5 × 10-11～1.8×10-11m2. Accordingly, the following can be obtained: the average permeability of the downhole surrounding rock is on the order of 10-11m 2. The determination of the permeability range of granite by the literature is 6.1X 10-12～9.5×10-11m2The calculations herein are consistent with the definition of this range.
Whether the fluid seepage complies with Darcy's law can be judged by utilizing the seepage Reynolds number. The reynolds number reflects the ratio of inertial and viscous forces in the flow of a fluid. A large number of researches show that the critical Reynolds number in seepage is 0.2-0.3, namely when the Reynolds number Re is less than or equal to the critical value, the seepage is linear seepage and obeys Darcy's law; when Re is greater than the critical value, the percolation is non-linear percolation and does not obey Darcy's law.
There are many methods for calculating the reynolds number, and currently, the methods are more general:
in the formula: re is Reynolds number;
v is the fluid seepage velocity, m/s;
k is the permeability of the medium, m2；
Mu is the dynamic viscosity coefficient of the fluid, Pa · s;
rho is the density of the fluid, kg/m3(ii) a Phi is the effective porosity,%, of the media.
To obtain the seepage Reynolds number according to equation (12), the values of the seepage velocity v, the rock mass medium permeability k and the effective porosity φ need to be obtained. The maximum porosity value of granite can reach 6.11%, and the effective porosity is0.05-2.8%, and the effective porosity of the whole bedrock is below 1%. The effective porosity of the mountain body around the underground roadway is calculated according to 2% because the effective porosity of the mountain body is increased due to the destructive effects of blasting and the like during the excavation and the like of the mountain body where the underground roadway is researched. According to the experimental result, the seepage velocity is calculated to be 0.9 multiplied by 10 by using the formula v ═ Q/A-4m/s. Substituting the relevant parameters into an equation (12) to obtain: re is 0.0005 < 0.2, namely the gas seepage in the experiment obeys Darcy's law.
Since the foregoing experiment was performed based on the assumption of Darcy's law, the assumption is true from the above analysis results, and the research process is justified.
Claims (7)
1. The method for evaluating the average permeability of surrounding rock of a broken granite tunnel is characterized by comprising the following steps of: the evaluation method comprises the following specific steps:
s1: firstly, a reversal rule of the air seepage direction of surrounding rocks of the roadway in summer and winter is revealed through long-time monitoring and analysis;
s2: then, based on Darcy law, deducing a roadway surrounding rock average permeability evaluation model;
s3: finally, a pressurization test is adopted, a method for determining the gas seepage critical inflation pressure of the surrounding rock of the roadway is provided, and a set of evaluation technology suitable for the average permeability of the surrounding rock of the underground roadway with the complex structure is formed.
2. The method for evaluating the average permeability of surrounding rocks of a broken granite roadway according to claim 1, wherein: the specific operation steps in the step S1 are as follows:
the method comprises the following steps: arranging an air door at a position 100m away from a roadway opening in the roadway to serve as a measuring section of natural ventilation;
step two: the shape and size of the ventilation sectional area of the air door are controlled by adjusting the number of the spliced door plates on the retaining wall;
step three: 3 measuring points are distributed on the measuring section, an electronic breeze meter is adopted to measure the wind speed, temperature monitoring points are arranged at the positions 20m away from the roadway opening on the inner side and the outer side of the roadway, a multi-parameter meteorological sensor is adopted to measure the temperature, and the measured wind speed data and the measured temperature data are recorded.
3. The method for evaluating the average permeability of surrounding rocks of a broken granite roadway according to claim 1, wherein: the radon concentration in summer is 7.5 multiplied by 104Bq/m3The radon concentration in winter is lower than 300Bq/m3The concentration of radon in spring and autumn is between that in winter and summer.
4. The method for evaluating the average permeability of surrounding rocks of a broken granite roadway according to claim 1, wherein: the specific operation steps in the step S2 are as follows:
the method comprises the following steps: processing the mountain body where the roadway is located into a uniform porous medium;
step two: and deducing a surrounding rock average permeability calculation model by adopting Darcy's law.
5. The method for evaluating the average permeability of surrounding rocks of a broken granite roadway according to claim 1, wherein: the specific operation steps in the step S3 are as follows:
the method comprises the following steps: a sealing door is arranged at the mouth of the experimental underground roadway, and a ventilation measuring section is arranged at a position 150 meters away from the mouth of the underground roadway;
step two: closing a closed door of a tunnel junction of the underground tunnel, then opening fans in two fan rooms, carrying out press-in ventilation on the underground tunnel, and adjusting inflation pressure in the underground tunnel by changing the opening of the door;
step three: respectively measuring ventilation data when a closed door of the underground tunnel junction is opened and closed, and simultaneously monitoring and recording radon concentration at a wind speed measurement section;
step four: and calculating whether the fluid seepage obeys Darcy law according to the seepage Reynolds number.
6. The method for evaluating the average permeability of surrounding rocks of a broken granite roadway according to claim 5, wherein: and measuring three groups of data in each state by using the ventilation and radon concentration data measured in the third step, and averaging the results.
7. The method for evaluating the average permeability of surrounding rocks of a broken granite roadway according to claim 5, wherein: the critical Reynolds number in seepage in the step four is 0.2-0.3.
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| 王曙光,牛冠毅,宋碧宏,杨伟: "氡在破碎花岗岩巷道及围岩中的运移机制解析", 《地下空间与工程学报 》 * |
| 王曙光: "机械通风条件下巷道围岩的氡析出规律", 《后勤工程学院学报》 * |
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| CN110837695B (en) | 2023-06-27 |
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