CN111257191A

CN111257191A - Chemical clogging measurement method for geotextile

Info

Publication number: CN111257191A
Application number: CN202010076193.4A
Authority: CN
Inventors: 肖明清; 龚彦峰; 李鹏飞; 周旋; 张顶立; 王克金; 孙文昊; 唐曌; 徐晨; 王少锋
Original assignee: China Railway Siyuan Survey and Design Group Co Ltd
Current assignee: China Railway Siyuan Survey and Design Group Co Ltd
Priority date: 2020-01-23
Filing date: 2020-01-23
Publication date: 2020-06-09

Abstract

The application discloses a geotechnical cloth clogging measuring method. The geotechnical cloth clogging measuring method comprises the following steps: laying geotextile to be tested on the bottom surface of the test box of the measuring device; injecting an ion solution into the test box; circulating the ionic solution through the geotextile while maintaining the ionic solution in the test chamber at a predetermined height; and measuring the displacement through the geotextile at a first time interval. According to the geotechnical cloth silting measurement method, the ion solution is prepared to replace water so as to simulate groundwater rich in a large amount of ions to permeate geotechnical cloth, and the ion crystallization condition is chemical silting, so that the performance of the geotechnical cloth subjected to water-rich silting is better met, and more real and effective data can be provided.

Description

Chemical clogging measurement method for geotextile

Technical Field

The invention belongs to the field of water seepage and blockage prevention of tunnels, and particularly relates to a chemical clogging measurement method for geotextile.

Background

The functions of the geotextile in engineering can be roughly divided into a reinforcing and stabilizing function, a filtering function, an isolating function, a drainage function, a waterproof (seepage-proofing) function, a protection function and a plurality of functions.

In the existing silting test, the physical silting condition of the geotextile under the effect of filling soil particles is mainly researched. In the tunnel of water-rich karst rock, the underground water contains a large amount of Ca²⁺、Mg²⁺、SO₄ ^2-And HCO₃ ^-Plasma, the surface and interior of geotextile will be subjected to ionic crystallization (mainly CaCO) during long-term seepage₃) Chemical clogging of the geotextile can occur due to the influence of the precipitation. And because the rock tunnel is different from the sandy soil tunnel, most of rocks around the tunnel are complete, cracks are not developed completely, and fine-grained soil is not easy to enter the surface and the interior of the geotextile, the clogging of the geotextile is mainly chemical crystallization clogging in the water-rich karst tunnel. The clogging condition of chemical crystallization is not considered in the existing clogging test.

Disclosure of Invention

In view of the above, the main objective of the present invention is to provide a method for measuring clogging of geotextile, in which an ionic solution is used for circulation, so that the clogging condition of ion-rich groundwater permeating the geotextile can be simulated, and the performance of geotextile after rich water clogging can be better met, thereby providing more real and effective data.

The invention provides a geotechnical cloth clogging measuring method which comprises the following steps:

laying geotextile to be tested on the bottom surface of the test box of the measuring device;

injecting an ion solution into the test box;

circulating the ionic solution through the geotextile while maintaining the ionic solution in the test chamber at a predetermined height; and

the amount of water displaced through the geotextile is measured at a first time interval.

According to one embodiment of the invention, the ionic solution has a composition that simulates the flow of water over an actual engineered geotextile. The water flow above the actual engineering geotextile can be underground water rich in ions, and the water flow component of the underground water is different according to different geological conditions and can contain different types of ions. In particular, groundwater may contain a large amount of Ca²⁺、Mg² ⁺、SO₄ ^2-And HCO₃ ^-Plasma, but is not limited thereto.

In practical engineering, the surface and the inside of the geotextile can be affected by ion crystallization precipitation, wherein CaCO is the main possibility₃And (4) precipitating. Preferably, the ionic solution contains Ca at a predetermined concentration²⁺And HCO₃ ^-。

More preferably, the ionic solution is prepared by adding a predetermined concentration of CaCl₂Solution and predetermined concentration of NaHCO₃After the solutions are mixed, the ionic solution is adjusted to be alkaline.

Specifically, a predetermined concentration of CaCl₂Solution and predetermined concentration of NaHCO₃The solution is mixed, at which time Ca²⁺And HCO₃ ^-Can coexist in the solution in large quantity, and after injecting the solution into the test box for circulation, further injecting an alkaline solution into the test box to adjust the whole mixed solution to be alkaline, at the moment, HCO₃ ^-Can be reacted with OH^-Reaction to CO₃ ^2-，CO₃ ^2-Continuously react with Ca²⁺Reaction to form CaCO₃And (4) precipitating. Used for simulating ionic crystallization (mainly CaCO) of geotextile in actual engineering₃) Fouling of the precipitate.

According to one embodiment of the invention, the concentration of each ion in the ionic solution is kept constant during the circulation of the ionic solution.

Specifically, keeping the concentration of each ion in the ionic solution constant is performed by detecting the concentration of each ion in the ionic solution at a second time interval and replenishing the corresponding ion whose ion concentration is reduced. The second time interval may be 0.5-1.5 h, but is not limited thereto. The method of detecting the concentration of each ion in the ionic solution may be a titration method, but is not limited thereto. Taking the ions in the ionic solution as Ca²⁺For example, a part of the ionic solution in the test chamber is taken out and used as a water sample, an alkaline solution is added to adjust the pH value of the ionic solution, and then a trace amount of calcium red indicator, namely Ca, is added to the water sample²⁺The complexing solution of the calcium red indicator is purple red, and the titration is carried out by adopting an Ethylene Diamine Tetraacetic Acid (EDTA) solution with a certain concentration, and the EDTA can capture Ca in the complex²⁺When the titration is finished, the calcium red indicator is completely released, and the solution turns blue. Ca in the water sample can be calculated according to the stoichiometric ratio of the reaction²⁺The concentration of (c). CaCO as the ionic solution circulates in the test chamber₃Gradually depositing the solution on the geotextile, gradually reducing the ion concentration in the ionic solution, and supplementing corresponding reagents at the moment so as to keep the ion concentration of the ionic solution in the test chamber unchanged.

According to one embodiment of the invention, after the geotextile to be tested is laid, the soil sample is added into the test box and tamped, and then the ionic solution is injected. Specifically, a soil sample is added into the test box and tamped to simulate the physical clogging condition, then an ion solution is injected into the test box to simulate the chemical clogging condition, and the combination of the two conditions is the simulation of the coupling clogging condition.

According to an embodiment of the present invention, the first time interval is 2-4 hours. Those skilled in the art will appreciate that the time interval between measuring the displacement through the geotextile may be shorter or longer depending on the actual test requirements.

The method for measuring the clogging of the geotextile is suitable for the clogging measuring devices of various geotextile application scenes. Different clogging measuring devices can be designed for simulation according to different scenes of the geotextile applied in the actual engineering, and the geotextile clogging measuring method is also suitable for the clogging measuring devices.

According to one embodiment of the invention, the test box is provided with a water inlet and a water outlet, the bottom surface of the test box is provided with an arc-shaped plate to simulate the arch structure of the upper half part of the tunnel, and the arc-shaped plate is provided with a plurality of water drainage holes. Specifically, measuring the amount of water displaced through the geotextile at the first time interval includes measuring the amount of water displaced through each of the drainage holes at the first time interval. In this embodiment, the chemical fouling or coupling fouling of the geotextile in the simulated tunnel situation can be measured.

The measuring method according to the present invention may further include the step of taking out the geotextile to be measured and weighing the dry weight thereof after the water discharge amount is stabilized.

Preferably, the dry weight of the geotextile to be measured is the weight measured after the geotextile to be measured is air-dried.

According to the specific implementation mode aiming at the simulated tunnel, the dry weight of the geotextile corresponding to unit areas of different drainage holes can be measured respectively, so that the clogging conditions of the geotextile at different laying positions can be better mastered.

Depending on the embodiment of the simulated tunnel, the arc shape of the arc-shaped plate may correspond to the actual engineering design, and may for example consist of an arc of one or more circles. Preferably, the arc-shaped plate is a semicircular arc-shaped plate.

Compared with the actual engineering, the radius of the semicircular arc-shaped plate can be reduced according to the proportion of 1: 15-1: 5, preferably the proportion of 1: 10.

The radius of the semi-circular arc-shaped plate can be 0.3-1.0 m, for example, 0.4m, 0.5m, 0.6m, 0.7m, 0.8m or 0.9 m.

The longitudinal length of the arc plate is not particularly limited as long as the detection is convenient. For example, for a geotextile sample, the length of the arcuate panels can be any suitable length in the range of 0.2 to 0.8 m.

In this embodiment, the drain holes are arranged on the arc-shaped plates in a relative position simulating the arrangement of the annular blind pipes in the actual engineering.

Preferably, the drainage holes are arranged on the arc-shaped section of the semicircular arc-shaped plate at intervals of 20-40 degrees, preferably 25-35 degrees, of the central angle of the circle where the arc is located.

More preferably, the drainage holes are arranged on the arc-shaped section of the semicircular arc-shaped plate at intervals of 30 degrees of the central angle of the circle on which the arc is positioned.

According to an embodiment of the invention, the measuring device further comprises a water collecting tank and a variable frequency water pump, the ionic solution in the water collecting tank is conveyed to the test tank through the variable frequency water pump, and the ionic solution in the test tank is discharged through the water outlet and the water drain hole and flows into the water collecting tank to form circulation of the ionic solution. The variable-frequency water pump can adjust the water circulation rate according to the water level height required by measurement.

According to a particular embodiment, the water collection tank is arranged in the lower part of the test chamber. In this embodiment, the drain of the test chamber may be provided on its bottom surface. The outlet may be further provided with a screen or strainer to prevent loss of the soil sample during testing.

The variable frequency water pump may be disposed inside the water collection tank.

The test box can be provided with a plurality of water outlets (such as 2-10) and a plurality of water inlets (such as 4-40).

According to a specific embodiment, the water inlet of the test chamber may be arranged at the side of the test chamber. According to a specific embodiment, the water inlets may be evenly distributed on each side wall of the test chamber.

According to one embodiment of the invention, the test chamber may have at least two test chambers.

Preferably, the at least two test chambers are formed by dividing the arc-shaped plate by a partition perpendicular to the bottom of the test chamber.

Preferably, the at least two test chambers are in fluid communication with each other so that testing in each test chamber can be performed under the same test conditions; and/or the at least two test chambers are fluidly isolated from each other to enable independent circulation of ionic solutions so that tests in the respective test chambers may be performed under different test conditions.

According to a specific embodiment, the fluid communication or isolation between the chambers can be switched by means of valves or the like.

The arrangement of the plurality of test chambers can implement parallel tests, for example, tests of different geotextile samples under the same condition can be realized, and tests of one geotextile sample under different conditions can also be realized.

According to an embodiment of the present invention, the measuring device further includes a water distributor, an inlet of the water distributor is connected to the variable frequency water pump, and the water distributor has a plurality of water distribution ports to be respectively connected to the water inlets.

According to the geotechnical cloth silting measurement method, the ion solution is prepared to replace water so as to simulate groundwater rich in a large amount of ions to permeate geotechnical cloth, and chemical silting occurs due to ion crystallization, so that the condition of chemical silting of geotechnical cloth in the method is more consistent with the condition in a water-rich tunnel.

Drawings

FIG. 1 is a schematic structural view of a test apparatus according to an embodiment of the present invention;

FIG. 2 is a schematic view of the distribution of weep holes in the arc-shaped cross-section of an arc-shaped plate according to an embodiment of the present invention;

FIG. 3 is a top view of a test chamber of a test apparatus according to an embodiment of the present invention after geotextiles are applied to the test chamber;

FIG. 4 is a top view of a test chamber with a geotextile clogged therein in a test apparatus in accordance with an embodiment of the present invention;

fig. 5 is a diagram showing a change in a drainage flow rate of the tunnel short-filament geotextile at a drainage hole according to an embodiment of the present invention (an arc-shaped section of a semicircular arc-shaped plate);

fig. 6 is a diagram showing a change in a drainage flow rate of the tunnel short-filament geotextile at a drainage opening according to an embodiment of the present invention (another arc-shaped section of the semicircular arc-shaped plate);

fig. 7 is a graph showing a change in a drainage flow rate of the tunnel filament geotextile at a drainage opening according to an embodiment of the present invention (an arc-shaped section of a semicircular arc-shaped plate);

fig. 8 is a graph showing a change in a drainage flow rate of the tunnel filament geotextile at the drainage opening according to the embodiment of the present invention (another arc-shaped section of the semicircular arc-shaped plate);

the figure includes: 1-test box, 2-water collecting tank, 3-water separator, 31-water separating port, 4-water inlet, 5-water outlet, 6-arc plate, 61-water outlet and 7-baffle plate.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention and the accompanying drawings, and it is apparent 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 obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

The invention will be further explained below with reference to an exemplary embodiment shown in the drawing. Various advantages of the present invention will become more apparent from the following description. Like reference numerals in the drawings refer to like parts. The shapes and dimensions of the various elements in the schematic drawings are illustrative only and are not to be construed as embodying the actual shapes, dimensions and absolute positions.

The invention mainly aims at the problem that the existing geotechnical cloth blockage test method can only measure the blockage condition of geotechnical cloth under the condition of water flow, but is difficult to simulate the real condition that the geotechnical cloth in underground water rich in a large amount of ions is influenced by ion precipitation. Therefore, the application provides a measuring method capable of simulating the clogging condition of the geotextile in the underground water rich in ions.

The physical silting refers to the condition that under the action of underground water, fine particles in sandy soil are changed into free particles under the action of osmotic force and are blocked on the surface and inside of the geotextile, and the water permeability of the geotextile is greatly reduced, particularly in water-rich sandy soil strata. In Ca²⁺And CO₃ ^2-In a water-rich sandy soil stratum with relatively low concentration, the clogging form of the geotextile is mainly physical clogging.

Chemical fouling as used herein refers to the formation of water-rich rock in a water-rich rock-soluble formation due to groundwater containing large amounts of Ca²⁺、Mg² ⁺、SO₄ ^2-And HCO₃ ^-Plasma, ion crystallization (mainly CaCO) during prolonged percolation₃) The block is in geotechnique's cloth's surface and inside, the condition of greatly reduced geotechnique's cloth water permeability. And because the rock stratum is different from the sandy soil stratum, the cracks are not developed completely, and fine-grained soil is not easy to enter the surface and the interior of the geotextile, therefore, Ca is added²⁺And HCO₃ ^-In the water-rich karst stratum with relatively high plasma concentration, the clogging form of the geotextile is mainly chemical clogging. The measuring method of the invention mainly aims at the measurement of chemical clogging.

Coupled fouling as used herein refers to the presence of both sand fines and relatively high concentrations of Ca in the water stream of a formation that incorporates the geological conditions described above under which chemical and physical fouling occur²⁺And HCO₃ ^-The plasma causes clogging of the geotextile.

Those skilled in the art will appreciate that the measurement method of the present invention is applicable to clogging measurement devices for various geotextile application scenarios. The measuring method of the present invention can be applied to various practical projects using geotextiles, such as tunnels, railways, tunnels and dams, but is not limited thereto.

The method for measuring the clogging of the geotextile comprises the following steps:

injecting an ion solution into the test box;

In the method of the present invention, the ionic solution has a composition that simulates the flow of water over an actual engineered geotextile. The water flow above the actual engineering geotextile can be underground water rich in ions, and the water flow component of the underground water is different according to different geological conditions and can contain different types of ions. In particular, groundwater may contain a large amount of Ca²⁺、Mg²⁺、SO₄ ^2-And HCO₃ ^-Plasma, but is not limited thereto.

For example, Ca²⁺The concentration of (b) can be 7-9 mmol/L, HCO₃ ^-The concentration of (b) can be 7-9 mmol/L.

More preferably, the ionic solution is prepared by adding a predetermined concentration of CaCl₂Solution and predetermined concentration of NaHCO₃After the solutions are mixed, the ionic solution is adjusted to be alkaline. Specifically, a predetermined concentration of CaCl₂Solution and predetermined concentration of NaHCO₃The solution is mixed, at which time Ca²⁺And HCO₃ ^-Can coexist in the solution in large quantity, and after injecting the solution into the test box for circulation, further injecting an alkaline solution into the test box to adjust the whole mixed solution to be alkaline, at the moment, HCO₃ ^-Can be OH^-With reaction to CO₃ ^2-，CO₃ ^2-Continuously react with Ca²⁺Reaction to form CaCO₃And (4) precipitating. Used for simulating ionic crystallization (mainly CaCO) of geotextile in actual engineering₃) Fouling of the precipitate. The specific reaction formula is as follows:

Ca²⁺+OH^-+HCO₃ ^-＝CaCO₃↓+H₂O

in particular, in actual geotextile engineering, ion-rich groundwater may contain a large amount of Ca²⁺And HCO₃ ^-And Ca (HCO)₃)₂With CaCO₃When the water body is collected to the outlet, the pressure is reduced, the balance of the reversible reaction is destroyed, and CO₂Overflow, reversible reaction towards formation of CaCO₃The precipitation direction is carried out, CaCO is gradually generated₃And precipitating, thereby causing chemical clogging of the geotextile. The specific reaction formula is as follows:

in the method for measuring clogging of the geotextile, in order to observe the clogging condition of the geotextile in the test time, Ca is adopted²⁺And HCO₃ ^-Adding an alkaline solution to adjust the whole mixed solution to be alkaline so that the reaction is directed to generate CaCO₃The direction of precipitation proceeds.

The preset height is not limited, and the clogging conditions of different types of geotextiles at the same water level height can be researched by controlling a variable method; similarly, the clogging conditions at different water level heights under the same type of geotextile can be studied by a controlled variable method. Generally, the larger the water level is, the larger the water head above the geotextile is, the larger the water pressure is, the larger the flow rate is, and finally the clogging condition of the geotextile is more serious.

The expression of the data result needs to be considered in the setting of the certain time interval, and the shorter the time interval is, the more data points are collected, and the more accurate the test result is. Meanwhile, the time interval is too long, which may cause inaccurate trend of test result expression. The certain time interval can be 2-4 h, and is preferably 3 h.

And in the circulation process of the ionic solution, keeping the concentration of each ion in the ionic solution unchanged.

Specifically, keeping the concentration of each ion in the ionic solution constant is performed by detecting the concentration of each ion in the ionic solution at a second time interval and replenishing the corresponding ion whose ion concentration is reduced. The second time interval may be 0.5-1.5 h, but is not limited thereto. The concentration of each ion in the ionic solution is detected in order to keep the concentration of each ion constant during the circulation. It may be exemplified that the method of detecting the ion concentration in the ionic solution may be a titration method, but is not limited thereto.

Taking the ions in the ionic solution as Ca²⁺For example, a part of the ionic solution in the test chamber is taken out and used as a water sample, an alkaline solution is added to adjust the pH value of the ionic solution, and then a trace amount of calcium red indicator, namely Ca, is added to the water sample²⁺The complexing solution of the calcium red indicator is purple red, and EDTA solution with certain concentration is adopted for titration, and the EDTA can capture Ca in the complex²⁺When the titration is finished, the calcium red indicator is completely released, and the solution turns blue. Ca in the water sample can be calculated according to the stoichiometric ratio of the reaction²⁺The concentration of (c). CaCO as the ionic solution circulates in the test chamber₃Gradually depositing the solution on the geotextile, gradually reducing the ion concentration in the ionic solution, and supplementing corresponding reagents at the moment so as to keep the ion concentration of the ionic solution in the test chamber unchanged.

Specifically, 50mL of ionic solution in the test chamber is taken out as a water sample, 20mL of NaOH solution (with the concentration of 0.1mol/L) is added to adjust the pH value, a trace calcium red indicator is added, the solution is purple red, the EDTA solution with the concentration of 0.1mol/L is used for titration, the speed is slow when the end point is close, and the end point is obtained when the solution is changed from purple red to bright blue. Ca in water sample²⁺The concentration (X) is:

it will be appreciated by those skilled in the art that the measurement methods of the present invention include, but are not limited to, chemical fouling or coupling fouling. According to the measuring method, after the geotextile to be measured is laid, the soil sample is added into the test box and tamped, and then the ion solution is injected. Specifically, a soil sample is added into the test box and tamped to simulate the physical clogging condition, then an ion solution is injected into the test box to simulate the chemical clogging condition, and the combination of the two conditions is the simulation of the coupling clogging condition.

In the measurement method for simulating coupling clogging, similar to the measurement method for simulating physical clogging, the circulating liquid is an ionic solution simulating chemical clogging.

Specifically, in the measurement method for simulating physical clogging, after geotextile to be measured is laid in the test box, the geotextile is covered by a soil sample and tamped; starting water circulation by maintaining the water level in the test tank at a predetermined height; the amount of water discharged from the individual weep holes is measured at regular intervals.

And the tamping is carried out by adding the soil sample in batches to tamp the soil sample in batches so as to lead the compactness of the soil sample to be consistent. Preferably, the consistency of the compactness of the soil sample is determined by measuring and controlling the height change of each batch of soil sample before and after tamping. More preferably, the soil sample is tamped to make the compactness of the soil sample close to the compactness of the soil layer on the upper part of the actual tunnel when measured.

The compactness of the soil sample within test chamber 1 can be characterized by quantifying the density of the soil sample, but is not limited thereto.

The preset height is not limited, and the physical clogging conditions of different types of geotextiles at the same water level height can be researched by controlling a variable method; similarly, physical clogging conditions at different water level heights can be studied by a controlled variable method with the same type of geotextile. In general, the larger the water level height, the larger the water head above the drain hole 61, the larger the water pressure, and the larger the flow rate, and finally the more clogging of the drain hole becomes.

Those skilled in the art will appreciate that the measurement method of the present invention is applicable to clogging measurement devices for various geotextile application scenarios. The measuring method of the present invention can be applied to various practical projects where geotextiles are applied and ion-rich groundwater exists, such as tunnels, railways, tunnels and dams, but is not limited thereto.

The clogging measuring method is particularly suitable for a tunnel geotextile clogging measuring device. The tunnel geotextile clogging measuring device is specifically described by the specific example shown in fig. 1.

Fig. 1 shows a schematic structural view of an example of a tunnel geotextile clogging measuring device. Referring to fig. 1, the measuring device is shown with a test chamber 1, a water collection tank 2 and a variable frequency water pump (not shown).

The bottom surface of the test box 1 is provided with an arc-shaped plate 6 and forms a part of the bottom surface, and the arc-shaped plate 6 is provided with a plurality of water drainage holes 61.

The main difference between the geotextile clogging measuring device shown in fig. 1 and the conventional geotextile clogging measuring device is that the bottom surface of the test box 1 is provided with an arc-shaped plate 6 provided with a plurality of water drainage holes 61, so that the arch structure and the water flow condition of the upper half part of the tunnel can be simulated.

The cross-sectional shape of the arc-shaped plate 6 is a part of an arc of a circle. Preferably, the arc is semi-circular. In this example, the arc 6 is a semicircular arc.

The arc radius of the arc-shaped plate 6 can be reduced to 1: 15-1: 5, preferably 1:10 according to the actual engineering proportion. The arrangement of scaling down according to actual engineering can better simulate the arch structure of the tunnel and provide more real and effective measurement data. An exemplary radius of the arc may be 0.5m, but is not limited thereto, and may be set according to specific needs.

The length of the arc 6, which may be the same as the width of the test chamber, may be set according to the width of the test chamber 1. The length of the arc-shaped plate can be 1.4m for example, but is not limited to this, and can be set according to specific needs.

As shown in fig. 1, the arc plate 6 is provided with a drain hole 61. The arrangement of the drain holes 61 simulates the design of an annular blind pipe in the existing engineering. Through set up the outlet on the arc, rather than adopting the screen cloth to constitute the arc, the actual rivers condition of the inhomogeneous distribution in the simulation engineering can be better to the stifled condition of silt of geotechnological cloth is surveyd better.

The bleed openings 61 can be spaced at different angles for different arcs (different radii and/or different central angles). For example, they may be spaced at intervals of 20 to 40, preferably 25 to 35. As shown in fig. 2, in this example, the arc-shaped plate 6 is a semi-circular arc-shaped plate, and the drainage holes are arranged on the cross section of the arc-shaped plate at intervals of 30 ° with respect to the central angle of the circle on which the arc is located, that is, there may be 5 drainage holes 61 on the semi-circular arc-shaped cross section of the arc-shaped plate 6, which are located at 30 °, 60 °, 90 °, 120 ° and 150 °, respectively. At this time, the drainage holes 61 positioned at 30 degrees and 150 degrees are symmetrically distributed and belong to the arch waist position; the drainage holes 61 positioned at 60 degrees and 120 degrees are symmetrically distributed and belong to the positions of arch shoulders; the drain hole 61 located at 90 ° belongs to the dome position.

The rows of drainage holes may be arranged at different intervals for different lengths of the arc-shaped plates, and the present invention is not particularly limited thereto. For example, the arrangement of the ring-shaped blind pipe in the actual engineering can be set. For example, the distance may be 15 to 35cm, preferably 20 to 30 cm. In this example, the length of the arc 6 is 1.4m, and 4 drain holes are provided at an interval of 25cm on the arc, respectively at four cross sections of 25cm, 50cm, 100cm and 125cm of the arc 6.

The shape of the drain holes 61 is not particularly limited, and may be, for example, circular, oval, square, rhombic, or the like. In this example, the shape of the drain hole is circular.

The size of the drain hole 61 can be determined according to the size of a boiling water hole of a tunnel drainage blind pipe, and generally can be 5-8 mm, and the size of the drain hole can be 5mm, 6mm, 7mm, 8mm and the like.

The exterior of the weep hole 61 is connected to the drain system and the interface needs to be sealed to prevent leakage. The connection part between the outside of the drain hole and the drainage system is a pagoda joint, and the interface is sealed by a hot melting machine, but the connection part and the sealing mode are not limited to this, and other modes can be selected according to specific situations.

With further reference to fig. 1, the ionic solution in the water collection tank 2 is conveyed to the test chamber 1 by a variable frequency water pump (not shown), and the ionic solution in the test chamber 1 is discharged through the water discharge port 5 and flows into the water collection tank 2 to form a circulation of the ionic solution.

The variable frequency waterThe pump can adjust the water pressure by adjusting the rotation speed of the motor, and further control the inflow and outflow rates of the ionic solution of the test chamber 1. In this example, the variable frequency water pump can be a submersible pump, and the submersible pump can be placed in the water collecting tank 2, with the rated lift of 36m and the rated flow of 3m³/h。

In particular, the device shown in fig. 1 also comprises a water separator 3. Wherein, the ionic solution in the header tank 2 is carried to the water knockout drum 3 through the frequency conversion water pump, and the water knockout drum 3 can be used to shift the ionic solution that the frequency conversion water pump provided to different water inlets. The variable frequency water pump is connected with the inlet of the water separator 3 through a pipeline (such as a galvanized iron pipe). The water distributor 3 is provided with a plurality of water distribution openings 31, and the water distribution openings 31 are connected with pipelines through connecting parts and further connected with the water inlets 4 respectively. Also, a seal is required at the interface to prevent leakage. In this example, the center of the water separator 3 is a water accumulation circular groove, and 12 water separation ports 31 are arranged on the groove; the water diversion port 31 is connected with the pipeline through a pagoda joint, and a raw adhesive tape needs to be wound between the water diversion port 31 and the pagoda joint to prevent leakage; sealing between the pagoda joint and the pipeline through a hot melting machine to prevent leakage; and the other end of the pipeline is hermetically connected with the water inlet 4 by installing a quick-connection plug.

A water pressure gauge (not shown) can also be arranged at the outlet of the water diversion port 31 so as to observe different water pressures of the water inlet 4.

With further reference to fig. 1, the water inlet 4 is disposed at a side surface of the test chamber 1, and the water outlet 5 is disposed at a bottom surface of the test chamber 1. The ion solution is injected into the test chamber 1 through the water inlet 4, and the ion solution in the test chamber 1 is discharged through the water outlet 5 and the drain hole 61, and flows into the water collection tank 2. The number of the water inlets 4 and the water outlets 5 is respectively multiple, the specific number can be set according to the specific conditions such as the size of the test chamber 1, the distribution arrangement mode of the side surface or the bottom surface of the test chamber, and the inflow and outflow rates of the ionic solution can be regulated and controlled (for example, through a valve).

In this example, the test chamber 1 is provided with 28 water inlets 4, two rows of water inlets 4 are arranged on both the front and back side surfaces of the test chamber 1, the height of the first row of water inlets 4 from the bottom surface of the test chamber 1 is 25cm, and the height of the second row of water inlets 4 from the bottom surface of the test chamber 1 is 75 cm. Three rows of water inlets 4 are arranged on the left side surface and the right side surface of the test box 1, and each row is provided with 3 water inlets 4; the second row of water inlets 4 is located in the middle of the test chamber 1 in the width direction, and the first and third rows of water inlets 4 are respectively 25cm away from the boundary of the test chamber 1. The diameter of the water inlet 4 can be 15-25 cm, and is preferably 20 cm.

The water inlet 4 needs to be fitted with a sealing member to be sealed. The sealing means of the water inlet 4 can be exemplified by a quick-connect coupling seal.

In this example, the bottom surface of the test chamber 1 is provided with 4 water outlets 5, and the diameter of the water outlets 5 may be 20-30 cm, preferably 25 cm.

The test chamber of the measuring device of the present invention may further have a top cover (not shown). The top cover and the box body need to be fixed and sealed. In this embodiment, the top cover and the box body can be fixed by screws, but not limited thereto; meanwhile, the top cover and the box body can be sealed through a sealing bead, but the sealing bead is not limited to the top cover and the box body.

The test chamber of the inventive metrology apparatus may have two or more test chambers. The arrangement of two or more test chambers can simultaneously research the clogging conditions of two or more kinds of geotextiles, thereby not only shortening the test time and improving the test efficiency, but also reducing the errors caused by repeated tests and improving the test precision. For example, the test chamber may have 2 to 10, preferably 2 to 5, more preferably 2 or 3 chambers.

The at least two testing chambers may be in fluid communication with each other, thereby ensuring that the water circulation conditions between the different chambers are the same and allowing parallel test testing.

The at least two test chambers may also be fluidly isolated from each other to enable independent water circulation, so that different water circulation conditions can be simulated in the same test.

The test chamber 1 may be divided into a plurality of chambers by providing partitions 7 in the test chamber 1, but is not limited thereto.

The fluid communication or fluid isolation between adjacent chambers can be controlled by providing on-off devices (e.g., valves) between the chambers.

As shown in fig. 1, in this example, the test chamber 1 is divided into two test chambers having the same area by providing a partition plate 7 at 75cm in the longitudinal direction of the arc-shaped plate 6. The height of the partition 7 may be, for example, 60cm, but is not limited thereto.

The shape of the test chamber 1 is not particularly limited, and may be a rectangular parallelepiped in general. The size of the test chamber 1 is set according to actual needs, and may be, for example, 2m × 1.5m × 1m (length × width × height), but is not limited thereto.

The shape of the header tank 2 is not particularly limited, and may be, for example, a rectangular parallelepiped. The size of the header tank 2 may be, for example, 3m × 1m × 0.9m (length × width × height), but is not limited thereto.

The material of the test chamber 1 suitable for the present invention is not particularly limited, but is required to be able to bear the pressure required for the test. For example, the stainless steel plate may be welded, and the thickness of the stainless steel plate may be 5 to 15mm, preferably 10 mm.

The material of the water collection tank 2 suitable for the present invention may be the same as or different from that of the test chamber 1. For example, the stainless steel plate is welded, and the thickness of the stainless steel plate can be 3-7 mm, preferably 5 mm.

In the invention, the test box 1 and the water collecting box 2 can be made of stainless steel, and after the stainless steel is contacted with the ionic solution and air for a long time, a large amount of iron rust (Fe) is generated on the inner side of the box body₂O₃) The specific chemical reaction equation is as follows:

4Fe+6H₂O+3O₂＝4Fe(OH)₃

2Fe(OH)₃＝Fe₂O₃+3H₂O

the generated rust can be attached to the surface of the geotextile along with the ionic solution and causes certain clogging of the geotextile. In order to prevent the formation of a large amount of rust, the inside of the test chamber 1 and the header tank 2 was entirely painted before the test to isolate air and water.

The embodiment adopts the tunnel geotextile silting measuring device to carry out the chemical silting measurement

Firstly, the tunnel geotextile clogging measuring device is checked to ensure that the phenomena of water leakage and blockage do not occur. This is because water leakage and clogging of the test apparatus significantly affect the test results, and therefore, it is necessary to inspect the test apparatus before the start of the actual test.

The inspection process was as follows: first, the water collection tank 2 is checked for water leakage. Injecting water into the water collecting tank 2 to a specified height, observing and measuring the height of the water level after 1h, and if the height of the water level is not changed, proving that the water collecting tank 2 does not leak water; if the water level is lowered, it is proved that the water collection tank 2 has a water leakage phenomenon, and the water collection tank 2 needs to be inspected and maintained. Next, the test chamber 1 is checked for water leakage or clogging at the water inlet 4, the water outlet 5, the drain hole 61, and the like. Switching on a transformer power supply, switching on a water pump to the transformer, adjusting the rotating speed of the water pump to a proper value, conveying water in a water collecting tank 2 to a test box 1 through a water separator 3 (checking whether water leakage exists at each joint in the process, if water leakage is found, starting a test after water stopping treatment is needed), turning off the water pump after the water level of the test box 1 reaches a specified water level height, and checking whether water drainage of each water outlet 5 is smooth one by one in the process; if there is a clogged drain opening 5, the test is continued after cleaning in time and normally. Observing and measuring the water level height in the test box 1 after 1h, and if the water level height is not changed, proving that the test box 1 is watertight; if the water level is lowered, the water leakage phenomenon of the test box 1 is proved, and the test box 1 needs to be checked and maintained again. Finally, after the inspection is completed, the drain port 5 of the test chamber 1 and the header tank 2 is opened to drain all the water.

Then, the mass per unit area of the geotextile was measured.

The procedure for determining mass was as follows: since the test chamber 1 has dimensions of 2m × 1.5m × 1m (length × width × height), the thickness of the stainless steel plate on each side of the test chamber 1 is 10mm, and the radius of the arc-shaped plate 6 is 0.5 m. At this time, the geotextile laid on the arc-shaped plate 6 has a length of 0.5 pi (about 1.57m), a width of 0.65m, and an area of about 1m². Specifically, the cutting of the geotextile sample should be accurate to 1 mm. The samples were divided into 3 groups, each group having 10 specimens and numbered. And weighing the geotextile samples one by one on a balance, wherein the reading precision of the balance is accurate to 0.1g。

The raw material of the geotextile should be selected in consideration of physical properties, chemical properties, service life and cost required in the application environment. In general, natural fibers are inferior to synthetic fibers in strength, aging resistance, acid and alkali resistance, corrosion resistance, etc., and therefore synthetic fibers such as polyester fibers (dacron), polypropylene fibers (polypropylene fibers), polyamide fibers (chinlon), polyvinyl acetal fibers (vinylon), polyacrylonitrile fibers (acrylon), etc., are mostly used as raw materials for geotextiles, and among them, polyester fibers and polypropylene fibers are mostly used. In this embodiment, two types of geotextiles, namely, a polyester filament geotextile and a polyester staple geotextile, are used.

Tailor geotechnological cloth according to the size of model box, with geotechnological cloth tiling on the arch face of proof box 1 inboard, extrude the inside air that exists from the vault to the tunnel bottom in proper order to simultaneously from the middle unnecessary air of discharging to both sides, then geotechnological cloth both sides edge is fixed with waterproof cloth, prevents that solution from flowing in from marginal space.

Further, referring to fig. 3, a top view of the test chamber of the test apparatus of one embodiment of the present invention is shown after laying the geotextile.

And finally, carrying out a chemical clogging test of the geotextile.

The procedure of the chemical fouling test was as follows: firstly, placing a bucket on an electronic scale, peeling, pouring water to a designated water level, and calculating the required calcium chloride (CaCl) according to a predetermined ion concentration₂) And sodium bicarbonate (NaHCO)₃) Mass, Ca in this example²⁺Has a concentration of 9mmol/L, HCO₃ ^-The concentration of (2) was 8 mmol/L. Weighing materials with corresponding mass by using an electronic scale, pouring the materials into a barrel, fully stirring, and slowly pouring the prepared chemical solution into the water collecting tank 2; the operation is repeated until the water level in the water collecting tank 2 reaches a designated height.

50mL of water sample in the water collecting tank 2 is taken and 20mL of sodium hydroxide solution (with the concentration of 0.1mol/L) is added to adjust the pH value. Adding trace calcium red indicator to obtain purple red solution. Titrating with EDTA solution of 0.1mol/L concentration at the near-end point at a slow speed, and making the solution purple redThe end point is the bright blue color, and the initial Ca content in the header tank 2 is measured and recorded²⁺The ion concentration. And (3) switching on a transformer power supply, switching on the water pump to the transformer, adjusting the rotating speed of the water pump to an appropriate value, conveying the solution in the water collecting tank 2 to the test box 1 through the water separator, adjusting the rotating speed of the water pump according to the flow of the water outlet 5 after the water level reaches a specified water level height, controlling the water level height in the test box 1 to be unchanged, and enabling the water level height in the test box 1 to be 75cm away from the box bottom at the moment.

Further, referring to fig. 4, a top view of a test chamber with a fouled geotextile in the test chamber of a test apparatus according to an embodiment of the present invention is shown.

Wait for the above CaCl₂And NaHCO₃After the solution in the test chamber 1 and the water collecting tank 2 is circulated and stabilized, a small amount of NaOH solution is added to adjust the whole mixed solution to be alkaline so as to generate CaCO₃And (4) precipitating.

After water circulation for 1h, 50mL of the medium water sample is taken from the water collecting tank 2, the operation is repeated, and the determined Ca is²⁺Concentration and initial Ca in the Water-collecting phase²⁺Comparing the concentrations to calculate Ca²⁺The amount of decrease in concentration, in combination with the change in water level in the header tank 2, calculates the mass of the relevant reagent to be replenished. Thereafter, Ca of the ionic solution in the header tank 2 was measured every 1 hour interval²⁺And (4) concentration. And meanwhile, the rotating speed of the water pump is adjusted according to the flow change at the drain hole, and the height of the water level in the test box is kept unchanged. After every 1h, the rotating speed of the water pump is repeatedly adjusted, and the height of the water level in the test box 1 is kept unchanged. If the water level in the test box 1 is lowered after the test is started, and a water leakage phenomenon exists, a waterproof spray gun can be used for local leakage compensation, so that the influence of the water leakage condition on the test is reduced as much as possible.

After the start of the water circulation, the amount of water discharged from the drain hole 61 for a certain period of time was measured at intervals of 3 hours by a measuring cylinder of a timer, and the experimental data was recorded. The flow rates of the drain holes 61 at different positions are calculated, and the function relation of the flow rate and the time is obtained.

Fig. 5 and 6 are graphs respectively showing the drainage flow change of the short-filament geotextile in the drainage holes on the two arc-shaped sections of the semicircular arc-shaped plates. Fig. 7 and 8 are graphs respectively showing the drainage flow change of the tunnel filament geotextile at the drainage holes on the two arc-shaped sections of the semicircular arc-shaped plates. The water discharge quantity of the water discharge holes of each section on the semicircular arc plate is continuously reduced along with the increase of time, and the water discharge quantity is kept basically stable after a period of time. The change curve of the water discharge is roughly divided into two stages, an initial flow rate reduction stage and a water discharge stabilization stage. In the initial flow reduction stage, particularly in the first 3h, the flow at the drain hole is rapidly reduced due to the formation of a large amount of crystallization precipitates and impurities and the accumulation of the impurities to cover the surface and the inner part of the geotextile; the change in flow rate at which the binder crystals continue to form the weep holes is then reduced but still continues to be reduced until 24 hours after which the flow rate remains substantially constant.

As shown in FIGS. 5 to 8. It can be seen from the figure that the flow rate at all three positions is continuously reduced (initial reduction stage) along with the increase of time and is approximately kept at a stable value (stable stage) after 24h, but it is obvious that the drainage flow rate of the drainage hole at each period of the arch waist (30 degrees and 150 degrees) is greater than that of the arch shoulder (60 degrees and 120 degrees) and greater than that of the arch top (90 degrees), which is probably caused by hydraulic gradient at different positions, hydraulic slope at the arch waist is greater than that of the arch shoulder and that of the arch top at the same water level, and the drainage at each point is increased along with the increase of the hydraulic slope at different positions. Although the drainage flow rates at different positions are different, the drainage flow rates of the drainage holes at different positions have the same trend of decreasing with time.

And finally, after 36 hours, closing a water pump switch, opening a water outlet 5 in the test box 1, completely discharging the ionic solution in the test box 1, further completely drying the geotextile from the test box 1, cutting the geotextile by using scissors, measuring the change of the mass of the geotextile at different positions after chemical clogging by using an electronic scale, wherein the reading precision is accurate to 0.1g, and measuring and recording the mass per unit area and the thickness of the geotextile at the positions after clogging by using a graduated scale.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention, and all modifications and equivalents made by the contents of the present specification and drawings, or directly/indirectly applied to other related technical fields, are included in the scope of the present invention.

Claims

1. The geotechnical cloth clogging measurement method is characterized by comprising the following steps:

injecting an ion solution into the test box;

2. The geotextile fouling measurement method of claim 1, wherein the ionic solution has a composition that simulates the flow of water over an actual engineered geotextile.

3. The geotextile fouling measurement method of claim 1, wherein said ionic solution comprises a predetermined concentration of Ca²⁺And HCO₃ ^-。

4. The geotextile fouling measurement method of claim 3, wherein said ionic solution is prepared by passing a predetermined concentration of CaCl₂Solution and predetermined concentration of NaHCO₃After the solutions are mixed, the ionic solution is adjusted to be alkaline.

5. The geotextile fouling measurement method of claim 1, wherein the concentration of each ion in the ionic solution is maintained constant during the circulation of the ionic solution.

6. The geotextile fouling measurement method of claim 5, wherein said maintaining the concentration of each ion in said ionic solution is performed by detecting the concentration of each ion in said ionic solution at a second time interval of 0.5 to 1.5h and replenishing the corresponding ion having a reduced ion concentration.

7. The geotextile clogging measuring method of claim 1, wherein said ionic solution is injected into said test chamber after laying the geotextile to be tested.

8. The method for measuring clogging of a geotextile of claim 1, wherein said first time interval is 2 to 4 hours.

9. The geotechnical cloth clogging measurement method according to any one of claims 1 to 8, wherein the test box is provided with a water inlet and a water outlet, the bottom surface of the test box is provided with an arc-shaped plate to simulate the arch structure of the upper half part of the tunnel, and the arc-shaped plate is provided with a plurality of water drainage holes.

10. The geotextile fouling measurement method of claim 9, wherein said measuring the amount of drainage through said geotextile at a first time interval comprises measuring the amount of drainage through each of the plurality of drainage holes at a first time interval.

11. The geotextile clogging measurement method of claim 10, further comprising removing the geotextile to be measured and weighing the dry weight thereof, when the drainage amount of each of the drainage holes is stabilized.

12. The method of measuring chemical clogging of a geotextile according to claim 11, wherein the dry weight of the geotextile to be measured is a weight measured after air-drying the geotextile to be measured.

13. The method of claim 9, wherein the arcuate shape of the arcuate plate conforms to actual engineering design.

14. The geotextile fouling measurement method of claim 13, wherein said arcuate panels are semi-circular arcuate panels.

15. The method for measuring clogging of a geotextile of claim 14, wherein the radius of the semicircular arc-shaped plate is reduced by 1:15 to 1:5 compared with that of an actual project.

16. The method for measuring clogging of a geotextile of claim 14, wherein the radius of the semicircular arc-shaped plate is 0.3 to 1.0 m.

17. The geotextile clogging measurement method of claim 9, wherein the plurality of drainage holes are arranged on the arc-shaped plate at positions corresponding to positions of circumferential blind pipes in simulation of actual engineering.

18. The method for measuring clogging of a geotextile of claim 17, wherein the drainage holes are arranged at intervals of 20 ° to 40 ° with respect to a central angle of a circle on which the arc is positioned on the arc-shaped cross section of the arc-shaped plate.

19. The geotextile fouling measurement method of claim 18, wherein the drainage holes are arranged at intervals of 30 ° from the central angle of the circle on which the arc is located on the arc-shaped section of the arc-shaped plate.

20. The geotextile clogging measurement method of claim 9, wherein said measurement apparatus further comprises a water collection tank and a variable frequency water pump, wherein the ionic solution in said water collection tank is transported to said test chamber by said variable frequency water pump, and the ionic solution in said test chamber is discharged through said water discharge port and said water discharge hole and flows into said water collection tank to form a circulation of said ionic solution.

21. The geotextile fouling measurement method of claim 9, wherein said test chamber has at least two test chambers.

22. The geotextile fouling measurement method of claim 21, wherein said at least two test chambers are formed by dividing said arcuate panels by a partition perpendicular to the bottom of said test chamber.

23. The geotextile fouling measurement method of claim 21, wherein said at least two test chambers are in fluid communication with each other or said at least two test chambers are in fluid isolation from each other to enable independent water circulation.

24. The geotextile clogging measurement method of claim 9, wherein the water inlet is provided at a side surface of the test chamber, and the water outlet is provided at a bottom surface of the test chamber.

25. The geotextile fouling measurement method of claim 20, wherein the measurement apparatus further comprises a water separator, an inlet of the water separator is connected to the variable frequency water pump, and the water separator has a plurality of water separation ports to be respectively connected to the water inlet ports.