CN106709139B - Method for measuring and calculating seepage flow of permeable layer of gravel-egg riverbed - Google Patents
Method for measuring and calculating seepage flow of permeable layer of gravel-egg riverbed Download PDFInfo
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- CN106709139B CN106709139B CN201611028213.0A CN201611028213A CN106709139B CN 106709139 B CN106709139 B CN 106709139B CN 201611028213 A CN201611028213 A CN 201611028213A CN 106709139 B CN106709139 B CN 106709139B
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Abstract
The invention discloses a method for measuring and calculating seepage of a permeable layer of an gravel-egg riverbed in the field of hydraulic and hydroelectric engineering. The method comprises the following steps of firstly measuring the water surface gradient under the condition of shallow water of the riverway in the dry season, then excavating a test pit to analyze the depth and width of an egg-gravel permeable layer, the porosity and the bed sand particle gradation, laying an egg-gravel layer according to the sampling gradation and the porosity to perform a seepage model test, obtaining seepage calculation parameters according to the fitting of test data, and amplifying according to the model similarity principle to obtain the seepage of the egg-gravel riverbed. The method makes up the blank of the calculation field of the seepage flow measurement of the permeable layer of the gravel river bed in the field of hydraulic and hydroelectric engineering, so that the seepage flow of the gravel river bed can be considered in design calculation such as minimum ecological flow release of a hydropower station, and the balance of a water environment ecological system of a river or a lake can be maintained.
Description
Technical Field
The invention relates to the field of water conservancy and hydropower engineering, in particular to a calculation method for seepage flow measurement of a permeable layer of an gravel-egg riverbed.
Background
The water pollution prevention and control action plan (ten items of water for short) proposes to scientifically determine ecological flow, strengthen water scheduling management of rivers, lakes and reservoirs, maintain ecological water requirements of rivers and lakes and guarantee ecological basic flow in a dry period. When the gravel permeable layer in the river bed is thick and the water depth of the river course is shallow, the seepage flow in the gravel permeable layer is even larger than the water flow above the river bed; when a small ecological flow is released to pass through a thicker pebble stone riverbed after the dam of the power station is built for water blocking, part of the flow flows below the surface of the riverbed in a seepage mode, so that the ecological base flow required for keeping the ecological environment in an area is insufficient, and the problem of seepage and overflow of the pebble stone permeable riverbed is emphasized in engineering design.
The river bed of the river in the southwest mountain area of China is mostly composed of pebbles, a pebble layer with a certain thickness on the surface of the river bed has strong water permeability, and a part of water flow flows in gaps of the pebbles in a seepage mode. Limited by the complexity of seepage hydraulic characteristics in the gravel layer of the river bed, the prior art level and practical understanding, only the flow above the river bed can be measured and calculated at present, most of the engineering practice only considers the flow above the river bed, and ignores the seepage in the gravel permeable layer. The measurement and calculation of the seepage flow in the gravel layer has no similar engineering and research results for reference, and a measurement and calculation method for the seepage flow of the gravel layer and the river bed is lacked.
Disclosure of Invention
In order to overcome the defects that the prior art can not measure and calculate the seepage flow of a gravel permeable layer, the designed ecological flow is small, the ecological balance is damaged, and the like, the invention aims to solve the technical problems that: provides a method for calculating the seepage flow of the permeable layer of the gravel-egg riverbed with higher accuracy.
The technical scheme adopted by the invention for solving the technical problems is as follows: the calculation method for the seepage flow rate of the permeable layer of the gravel-egg riverbed comprises the following steps:
a. under the conditions of small flow and shallow water depth of a river channel in a dry period, measuring a plurality of water surface gradients under the condition of shallow water in an engineering river reach, and recording a maximum value, a minimum value and an average value;
b. under the conditions of small river flow and shallow water depth in a dry period, digging pits in a river gravel permeable layer to analyze the depth and the width of the gravel permeable layer;
c. digging a cubic test pit with the side length of 1-2 m at the position, close to a water edge, of an oval stone river course beach, sealing the side wall and the bottom of the test pit by using waterproof plastic gummed paper, draining all the obtained oval gravels by using a filter screen, backfilling, injecting water until the whole test pit is submerged, recording the volume of the injected water and the volume of the test pit, and solving the ratio of the volume of the injected water and the volume of the test pit to obtain the porosity of a water permeable layer of the oval stone river bed;
d. screening and weighing the gravel and cobbles dug out of the test pit by using standard screening particle sizes, recording the weight of each particle size group, and analyzing and calculating the sand particle grading of the gravel and cobble bed;
e. according to the sampling data of the engineering river reach, laying a pebble layer in a rectangular water tank in a laboratory according to sampling gradation and porosity for carrying out a seepage model test, recording the flow rate of water flow passing through the water tank at different specific drops, and after the specific drop of the water tank is adjusted, recording the flow rate of surface water flow when the surface water flow is reduced to the pebble bed surface, wherein the flow rate is the seepage rate in the pebble layer at the corresponding specific drop of the river bed;
f. suppose Q is the seepage flow of the ovum gravel layer, the seepage flow Q and the bed surface gradient S form a positive correlation relationship, and S is AQ2+ BQ, substituting the test data in the step e into the formula to obtain parameters A, B, substituting the actual measurement ratio of the engineering river reach into the equation to solve to obtain the seepage flow in the pebble permeable layer water tank model, and finally amplifying according to the model similarity principle to obtain the seepage flow of the engineering river reachThe seepage flow rate.
Furthermore, the number of the drops measured in step a is 5 or more, the number of the test pits measured in step c is 3 or more, and the average value of the porosity is taken.
Furthermore, in the seepage model test in step e, a gravel sample is prepared in a water tank, and the thickness of the gravel layer is required to be more than 4 times of the maximum particle size of the bed sand grading.
Furthermore, when the flow measurement is carried out in the step e, the specific reduction of the water tank is adjusted according to the actual measured specific reduction of the riverbed, the specific reduction comprises the minimum value, the maximum value and the average value of the actual measured specific reduction, seepage flow data of different specific reductions except the three actual measured specific reductions, and the tested specific reduction and the corresponding seepage flow data are not lower than 10 groups.
Further, in the calculation of step f, polynomial fitting is performed on all the measured data of the slope S and the seepage flow rate Q in step e to obtain a seepage calculation parameter A, B.
The invention has the beneficial effects that: and performing model test measurement according to the grading and porosity of the sampled gravel bed sand particles through field sampling analysis to obtain model seepage flow, obtaining a seepage calculation formula of the river bed seepage flow and river reach specific drop under the conditions of the grading and porosity of the gravel bed sand particles, and performing amplification calculation according to a model similarity principle to obtain the engineering gravel river bed permeable river reach seepage flow.
Detailed Description
The calculation method for the seepage flow rate of the permeable layer of the gravel-egg riverbed comprises the following steps:
a. under the conditions of small flow and shallow water depth of a river channel in a dry period, measuring a plurality of water surface gradients under the condition of shallow water in an engineering river reach, and recording a maximum value, a minimum value and an average value;
b. under the conditions of small river flow and shallow water depth in a dry period, digging pits in a river gravel permeable layer to analyze the depth and the width of the gravel permeable layer;
c. digging a cubic test pit with the side length of 1-2 m at the position, close to a water edge, of an oval stone river course beach, sealing the side wall and the bottom of the test pit by using waterproof plastic gummed paper, draining all the obtained oval gravels by using a filter screen, backfilling, injecting water until the whole test pit is submerged, recording the volume of the injected water and the volume of the test pit, and solving the ratio of the volume of the injected water and the volume of the test pit to obtain the porosity of a water permeable layer of the oval stone river bed;
d. screening and weighing the gravel and cobbles dug out of the test pit by using standard screening particle sizes, recording the weight of each particle size group, and analyzing and calculating the sand particle grading of the gravel and cobble bed;
e. according to the sampling data of the engineering river reach, laying a pebble layer in a rectangular water tank in a laboratory according to sampling gradation and porosity for carrying out a seepage model test, recording the flow rate of water flow passing through the water tank at different specific drops, and after the specific drop of the water tank is adjusted, recording the flow rate of surface water flow when the surface water flow is reduced to the pebble bed surface, wherein the flow rate is the seepage rate in the pebble layer at the corresponding specific drop of the river bed;
f. suppose Q is the seepage flow of the ovum gravel layer, the seepage flow Q and the bed surface gradient S form a positive correlation relationship, and S is AQ2And + BQ, substituting the test data in the step e into the formula to obtain parameters A, B, substituting the actual measurement ratio of the engineering river reach into the equation to solve to obtain the seepage flow in the pebble permeable layer water tank model, and finally amplifying according to the model similarity principle to obtain the seepage flow of the engineering river reach.
The specific drop of the river reach is a main factor influencing seepage, so that the water surface specific drop under the condition of shallow water of the river reach is measured firstly, multiple groups of specific measurement are measured during measurement according to specific conditions, and the maximum value, the minimum value and the average value are taken for subsequent use; measuring the width and the depth of the gravel permeable layer to facilitate subsequent flow estimation; the excavation test pit is mainly used for analyzing the porosity of the gravel layer and the bed sand grain composition; carrying out a seepage model test after obtaining sampling data, setting the inclination of the water tank according to the gradient during the test, then introducing water into the water tank, slowly reducing the water flow after the water flow is stable, and when the surface water flow is reduced to the surface of the gravel bed, the flow at the moment is the seepage flow in the gravel river bed; the movement of water flow in the gravel permeable layer is driven by the hydraulic gradient generated by river channel gradient, and the hydraulic gradient in the gravel permeable layer of the natural open channel water flow can be approximately considered to be equal to the water surface gradient of shallow water. The seepage Q in the permeable layer is positively correlated with the bed surface gradient SSystem, S ═ AQ2+ BQ, is a seepage equation conforming to the Forchheimer form. And performing polynomial fitting in Excel according to the measured specific drop S and seepage Q data of the water tank model to obtain seepage calculation parameters A, B, substituting the measured specific drop of the river bed of the engineering river section into the equation to solve to obtain seepage in the water tank model of the water permeable layer of the pebble river section, and finally amplifying according to the measured width and depth of the water permeable layer according to the hydraulic model similarity principle to obtain seepage of the engineering river section.
Furthermore, the number of dips measured in step a is 5 or more, the number of test pits measured in step c is 3 or more, and the average value of the porosity is taken.
And e, when the seepage model test is carried out in the step e, preparing a gravel sample in the water tank, wherein the thickness of the gravel layer is required to be more than 4 times of the maximum grain size of the bed sand grading, and according to long-term experience and theoretical analysis, the arrangement mode can ensure that the error is reduced in the seepage measurement test process, so that the obtained result is more accurate.
And e, adjusting the specific drop of the water tank according to the actual measured specific drop of the riverbed during flow measurement in the step e, wherein the specific drop comprises the minimum value, the maximum value and the average value of the actual measured specific drop, and seepage flow data with different specific drops except the three actual measured specific drops, and the tested data is not lower than 10 groups. Because the specific drop of each section of the riverbed is different in practice, and the specific drop of the riverway is a key factor for determining the seepage flow, multiple groups of data can be tested as much as possible in the test.
In the calculation of the step f, all the measured data of the specific reduction S and the seepage Q in the step e are subjected to polynomial fitting in an excel table, then seepage calculation parameters A, B are obtained, the obtained conclusion is more universal after the fitting of multiple groups of data, and more accurate results can be obtained when the seepage of engineering river reach with similar bed sand grain gradation and porosity is estimated.
In the seepage model test, the proportion of seepage Q in the permeable layer is observed to increase along with the increase of the water tank ratio drop, and when the seepage is small, the water flows in a seepage mode almost in the gravel permeable layer. Therefore, when the river bed has large specific drop and small flow rate, the seepage rate of the gravel permeable layer cannot be ignored.
The invention provides a set of method capable of effectively measuring and calculating the seepage flow in the water permeable layer of the gravel-egg riverbed, which fills the blank of the calculation field of the seepage flow measurement of the water permeable layer of the gravel-egg riverbed in the field of hydraulic and hydroelectric engineering, so that the seepage flow of the gravel-egg water permeable riverbed can be considered in design calculation such as minimum ecological flow release of a hydropower station, and the balance of a water environment ecological system of a river or a lake can be favorably maintained. The engineering river reach seepage flow with bed sand grain composition and porosity close to each other can be calculated by referring to a seepage formula obtained by water tank model test data, so that a large amount of test cost is saved.
Claims (5)
1. The calculation method for the seepage flow rate of the permeable layer of the gravel-egg riverbed is characterized by comprising the following steps:
a. under the conditions of small flow and shallow water depth of a river channel in a dry period, measuring a plurality of water surface gradients under the condition of shallow water in an engineering river reach, and recording a maximum value, a minimum value and an average value;
b. under the conditions of small river flow and shallow water depth in a dry period, digging pits in a river gravel permeable layer to analyze the depth and the width of the gravel permeable layer;
c. digging a cubic test pit with the side length of 1-2 m at the position, close to a water edge, of an oval stone river course beach, sealing the side wall and the bottom of the test pit by using waterproof plastic gummed paper, draining all the obtained oval gravels by using a filter screen, backfilling, injecting water until the whole test pit is submerged, recording the volume of the injected water and the volume of the test pit, and solving the ratio of the volume of the injected water and the volume of the test pit to obtain the porosity of a water permeable layer of the oval stone river bed;
d. screening and weighing the gravel and cobbles dug out of the test pit by using standard screening particle sizes, recording the weight of each particle size group, and analyzing and calculating the sand particle grading of the gravel and cobble bed;
e. according to the sampling data of the engineering river reach, laying a pebble layer in a rectangular water tank in a laboratory according to sampling gradation and porosity for carrying out a seepage model test, recording the flow rate of water flow passing through the water tank at different specific drops, and after the specific drop of the water tank is adjusted, recording the flow rate of surface water flow when the surface water flow is reduced to the pebble bed surface, wherein the flow rate is the seepage rate in the pebble layer at the corresponding specific drop of the river bed;
f. suppose Q is the seepage flow of the ovum gravel layer, the seepage flow Q and the bed surface gradient S form a positive correlation relationship, and S is AQ2And + BQ, substituting the test data in the step e into the formula to obtain parameters A, B, substituting the actual measurement ratio of the engineering river reach into the equation to solve to obtain the seepage flow in the pebble permeable layer water tank model, and finally amplifying according to the model similarity principle to obtain the seepage flow of the engineering river reach.
2. The method for measuring and calculating seepage of a permeable layer of a pebble river bed according to claim 1, wherein the method comprises the following steps: the number of the drops measured in the step a is more than 5, the number of the test pits measured in the step c is more than 3, and the average value of the porosity is taken.
3. The method for measuring and calculating seepage of a permeable layer of a pebble river bed according to claim 1, wherein the method comprises the following steps: and e, when a seepage model test is carried out, preparing a gravel sample in the water tank, wherein the thickness of the gravel layer is required to be more than 4 times of the maximum particle size of the bed sand grading.
4. The method for measuring and calculating seepage of a permeable layer of a pebble river bed according to claim 1, wherein the method comprises the following steps: and e, adjusting the specific drop of the water tank according to the actual measured specific drop of the riverbed during flow measurement in the step e, wherein the specific drop comprises the minimum value, the maximum value and the average value of the actual measured specific drop, and seepage flow data with different specific drops except the three actual measured specific drops, and the tested data is not lower than 10 groups.
5. The method for measuring and calculating seepage of a permeable layer of a pebble river bed according to claim 4, wherein the method comprises the following steps: in the calculation of step f, polynomial fitting is performed on all the measured data of the specific drop S and the seepage flow Q in step e, and then seepage calculation parameters A, B are obtained.
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| US4388357A (en) * | 1979-01-23 | 1983-06-14 | True Temper Corporation | Sheet useful as a reservoir liner |
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| US4388357A (en) * | 1979-01-23 | 1983-06-14 | True Temper Corporation | Sheet useful as a reservoir liner |
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| 《长江三角洲地区小流域环境变化对水文过程影响研究》;徐金涛;《中国博士学位论文全文数据库 基础科学辑》;20120715(第7期);正文第41页 * |
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