CN111872095B - Flexible bushing and method for monitoring contaminated sites combined with flexible bushing - Google Patents

Abstract

The invention provides a flexible bushing and a polluted site monitoring method combined with the flexible bushing. The deployment of the flexible bushing in the monitoring well is to seal the borehole by arranging an impermeable cylindrical sleeve in the drilling space, so as to prevent the contamination of soil in the polluted site. Monitor the permeability coefficient and pollutant characteristics; select the corresponding type of vertical barrier according to the monitoring results, and use vertical barrier technology to treat the polluted site; continue to use the flexible bushing technology to monitor the pollution of the polluted site and its surrounding soil during the treatment period. Repair and block effects, and inject liquid medicine to repair according to actual needs. The invention can effectively monitor the pollutant characteristics of the polluted site through the flexible bushing technology, and can observe the changes of the pollutant concentration and permeability coefficient in the soil around the site in real time, thereby improving the restoration effect of the polluted site.

Description

Flexible bushing and method for monitoring contaminated sites combined with flexible bushing

technical field

The invention belongs to the technical field of control and treatment of polluted sites, and relates to a flexible bush and a polluted site monitoring method combined with the flexible bush.

Background technique

With the progress of society and economy, industry and agriculture continue to develop, and at the same time, the problem of soil pollution is becoming more and more serious. Heavy metal pollution such as chromium and nickel left in the soil by the waste and exhaust gas produced in the industrial production process after rainfall, and toxic and harmful substances such as polycyclic aromatic hydrocarbons and chlorinated hydrocarbons left in the soil due to the use of pesticides in the agricultural production process , are the inevitable soil problems that currently exist. The diffusion and migration of pollutants in the soil is a relatively complex process, including diffusion, convection, adsorption, etc., and is prone to multi-field coupling effects of chemical and temperature fields. Therefore, soil pollution has a wide range of influence in space, and various problems often have a chain reaction, causing damage to groundwater, the atmosphere and other ecological environments, so it is essential to control them.

In the treatment of various contaminated sites, in-situ remediation is the main means. In view of the long period of in-situ repair and the difficulty of complete repair, vertical isolation technology was proposed as a means of risk control and repair. During the construction of the vertical barrier, due to the cross flow of water in the soil layers at various depths, it is easy to cross-contaminate in the polluted site, causing the problem of aggravated pollution. In order to seal, bentonite is generally used to seal the boreholes in the early monitoring, but in fact, bentonite will cause some pollution to the repair site.

Contents of the invention

The present invention aims to provide a flexible bushing and a polluted site monitoring method combined with the flexible bushing. The method combines the vertical barrier with the flexible bushing technology, avoids cross-contamination, and measures the hydrological characteristics and pollutant characteristics of the site. At the same time, ensure that no trace pollutants leak during the restoration of the contaminated site, thereby improving the restoration effect of the contaminated site.

specific technical solutions;

Flexible bushing, including a cylindrical sleeve made of impermeable flexible material, the cylindrical sleeve is arranged in the drilling space, forming a tight sealing layer in the drilling space; the outer wall of the cylindrical sleeve is set at intervals A water-permeable and inner-sealed ring-shaped partition, which is connected to the temporary storage area at the bottom of the cylindrical sleeve through a hose; the cylindrical sleeve is connected to the aerodynamic device through an air guide tube; a sampling tube is provided in the temporary storage area , to sample the staging area.

The invention applies a new groundwater sampling technology—flexible bushing technology to the construction process of the vertical barrier. The use of flexible bushing technology can effectively find out the permeability coefficient and pollutant characteristics of the polluted site soil, and prevent cross-contamination and leakage of trace pollutants. In the cylindrical sleeve, ring-shaped partitions that are permeable on the outside and sealed on the inside are set at intervals. When sampling, the groundwater in the polluted site to be tested flows into the partition and enters the temporary tube at the bottom of the cylindrical sleeve through the hose in the partition. In the storage area, there are two conduits in the temporary storage area, namely the air guide tube and the sampling tube. Through the principle of air pressure and the downward check valve, the groundwater samples are introduced into the sampling bottles on the ground. During the monitoring of contaminated sites, flexible bushings are arranged around the site according to the previous site information, and the permeability coefficient and pollutant characteristics of the site soil can be measured more accurately. According to the monitoring results obtained, a specific construction plan combining vertical barriers, active PRB reaction walls and aeration method is formulated, and flexible linings are continued to be arranged on the outside. During the construction process, monitor the concentration of pollutants in the surrounding land to judge whether there is a leakage of pollutants or a breakdown of the vertical barrier. The data measured by the flexible bushing technology are used as the basis before construction and the real-time monitoring results during construction.

For this reason, a method of monitoring contaminated sites combined with flexible bushing technology is proposed. The use of flexible bushing technology in construction can not only temporarily seal the borehole, but also can be calculated by monitoring the falling speed of the downwardly expanding bush from the hole, using the obtained bushing deceleration data and pressure gauge readings. The permeability coefficient of the soil layer of the polluted site (the rock layer is the hydraulic conductivity coefficient, and the soil layer is the hydraulic conductivity coefficient). In addition, the analysis of the groundwater sampled by the flexible bushing technology can obtain the corresponding pollutant characteristics. According to these results, the vertical barrier type suitable for the target site can be determined to achieve a better restoration effect. The specific technical solutions are:

A method for monitoring contaminated sites combined with flexible bushing technology, comprising the following steps:

The first step: According to the distribution of pollution sources and the direction of groundwater flow, a flexible bushing is arranged in the monitoring well around the polluted site; the K value of the permeability coefficient of the seepage area of the polluted site is calculated by using the monitoring data of the flexible bushing. The rock layer is the permeability coefficient, and the soil layer is the hydraulic conductivity coefficient; sampling collects NAPL, that is, non-aqueous liquid phase samples, and analyzes the types of pollutants in the polluted site;

Step 2: According to the results obtained in the first step of monitoring, the corresponding vertical barrier type is determined from the K value of the permeability coefficient, the type and distribution of pollutants;

Step 3: While carrying out the construction of the vertical barrier, continue to use the flexible bushing to monitor, analyze the changes in the permeability coefficient of the soil around the polluted site, and whether the concentration and type of pollutants contained in it have changed; and use the flexible bushing according to actual needs Inject the corresponding liquid medicine for repair until the completion of the vertical barrier construction.

During the construction period, arrange flexible bushings in the original design monitoring points, place monitoring instruments and sensors in the flexible bushings, monitor the soil conditions around the polluted site in real time, analyze the operation status of the vertical barrier, and judge whether there is a partial breakdown of the barrier. Objects are repaired by injecting agents through the sleeve.

Further, according to the descending rate of the flexible bushing and the reading of the pressure gauge, the permeability coefficient K value is calculated.

In the treatment process of polluted sites, in order to achieve better treatment effects, vertical barrier technology is often used in combination with active PRB reaction wall, aeration and other technologies. In the process of combining multiple restoration techniques, how to carry out layout and design is the key point. The invention uses the hydraulic conductivity measured by the flexible bushing technology to identify the preferential water flow area, and cooperates with the hydraulic measurement results of the barrier to obtain the hydrogeological characteristics of the polluted area. At the same time, the analysis of groundwater samples in polluted areas obtained by sampling can obtain the characteristics of pollutants. Combined with the obtained information, the construction methods of the polluted site can be more reasonably designed and laid out to achieve better treatment effects. In addition, during the construction process, the monitoring equipment and corresponding sensors in the flexible bushing are used to monitor whether there is a slight leakage of pollutants or a breakdown of the separation wall. The barrier is repaired.

Compared with using vertical barriers, aeration method, and active PRB reaction wall alone, the contaminated site monitoring method combined with flexible bushing technology during the restoration process can effectively observe the characteristics of groundwater and pollutants, and at the same time understand the distribution of underground cracks . These factors may lead to a reduction in the effectiveness of pollutant treatment when vertical barriers are constructed. In addition, understanding the cracks in the ground and the distribution of groundwater is also conducive to choosing the appropriate construction machinery. In short, in the process of vertical barrier repairing contaminated sites, combined with flexible bushing technology to monitor contaminated sites, compared with general vertical barrier construction methods, it has its unique advantages and innovations, and is the key to improving the effect of contaminated site restoration. A reliable method.

To sum up, the present invention has beneficial effects: the flexible bushing is a feasible technology for fast sealing of boreholes, and the present invention combines vertical barrier construction with flexible bushing technology to effectively prevent cross-contamination during construction, It can also provide the permeability coefficient and pollutant characteristics of the polluted site soil, and prevent secondary pollution during the construction process.

Description of drawings

Fig. 1 is the structural schematic diagram of flexible bushing of the present invention;

Fig. 2 is the arrangement diagram of the monitoring points of the polluted site of the embodiment;

Fig. 3 is a component diagram of the embodiment detection water layer analysis analysis system;

Fig. 4 is the hypothetical liner deceleration curve figure of embodiment;

Fig. 5 is the schematic diagram of embodiment construction.

Detailed ways

The specific technical solutions of the present invention are described in conjunction with the examples.

As shown in Figure 1, the flexible bushing includes a cylindrical sleeve 5 made of impermeable flexible material, the cylindrical sleeve 5 is arranged in the drilling space, and a tight sealing layer is formed in the drilling space; in the cylindrical sleeve 5. On the outer wall, ring-shaped partitions that are permeable on the outside and sealed on the inside are arranged at intervals. The partitions are connected to the temporary storage area 3 at the bottom of the cylindrical sleeve 5 through flexible pipes; The aerodynamic device 4 is connected; the temporary storage area 3 is provided with a sampling tube 2 for sampling the temporary storage area 3 .

According to the preliminary investigation data of the polluted site, the arrangement position of the flexible bushing is determined, and the deployment density of the flexible bushing is increased in the seriously polluted area, as shown in Figure 2, where multiple flexible bushings are arranged around the polluted plot 7 for technical monitoring Point 6. Groundwater sampling and analysis are carried out according to the principle of flexible bushing technology.

Use the speed measuring device in the flexible bush to measure the falling speed of the bush in the hole, as shown in Figure 3, the component diagram of the detection water layer analysis and analysis system. The speed measuring device comprises a speed measuring device 8, a water injection pipe 9, a pressure gauge 10, and a sensor 11, and the device is put down by turning inward the bush winch 12.

According to the liner deceleration data, that is, the imaginary liner deceleration curve shown in Figure 4 and the reading P of the pressure gauge, the permeability coefficient K value of the seepage area is calculated (the rock layer is the water permeability coefficient, and the soil layer is the hydraulic conductivity coefficient).

In the formula: K is the permeability coefficient, m/s; k is the permeability, D, 1D=1m ² ; ρ is the fluid density, N·s ² /m ⁴ ; g is the gravity acceleration, m/s ² ; μ is the power Viscosity, N·s/m ² ; η is kinematic viscosity,

In the formula, Q is the seepage rate, m ³ /s; k is the permeability, D, 1D=1m ² ; A is the cross-sectional area of the hole, m ² ; △P is the pressure difference, that is, the pressure gauge reading, Pa; μ is fluid dynamic viscosity, Pa·s, namely N·s/m ² ; △L is seepage length, m.

ΔL=LL ₁ (3)

In the formula, △L is the seepage length, m; L is the total length of the borehole, m; _L1 is the length of the lowered casing, m.

Q=v·A (4)

In the formula, Q is the seepage rate, m ³ /s; v is the liner lowering speed, that is, the velocimeter reading, m/s; A is the cross-sectional area of the hole, m ² .

The hydrogeological characteristics of the polluted site are obtained according to the calculated permeability coefficient K value of the permeable area, and the characteristics of the pollutants 15 in the area to be treated are obtained by analyzing the groundwater samples. Combine the obtained information to determine the specific construction plan of the vertical barrier 14, determine whether to combine the active PRB reaction wall 13 and other technologies for construction, and install flexible bushings at the edge of the polluted site, as shown in Figure 5.

During the construction of the vertical barrier, due to human or natural factors, a small part of the barrier may be defective, resulting in the leakage of trace pollutants. Monitoring equipment or sensors should be continuously deployed in the flexible bushing during construction. Concentration of pollutants in the surrounding soil to determine whether a leak occurs.

Applying the flexible bushing technology to the construction of the vertical barrier can make the construction method more reasonable and improve the restoration effect of the polluted site.

Claims (3)

1. A pollution site monitoring method combining a flexible lining technology is characterized in that a flexible lining is adopted, the flexible lining comprises a cylindrical sleeve made of waterproof flexible materials, the cylindrical sleeve is arranged in a drill hole, and a tight sealing layer is formed in the drill hole; annular partition sections which are permeable to water at the outer side and sealed at the inner side are arranged on the outer wall of the cylindrical sleeve at intervals, and the partition sections are connected with a temporary storage area at the bottom of the cylindrical sleeve through hoses; the cylindrical sleeve is communicated with an aerodynamic device through an air duct; a sampling tube is arranged in the temporary storage area for sampling the temporary storage area;

the method comprises the following steps:

the first step is as follows: arranging the flexible bushing in the monitoring well at the periphery of the pollution site according to the distribution condition of pollution sources and the water flow direction of underground water; calculating the permeability coefficient K value of the water seepage area of the polluted site by using the monitoring data of the flexible lining, wherein the rock stratum is the water permeability coefficient, and the soil layer is the hydraulic conductivity coefficient; sampling and collecting NAPL (non-aqueous phase liquid phase) samples, and analyzing the pollutant types of the polluted site;

the second step: determining the corresponding vertical barrier type according to the result obtained by the monitoring in the first step and the permeability coefficient K value, the pollutant types and the distribution;

the third step: monitoring by using the flexible lining while constructing the vertical barrier, and analyzing the change of the permeability coefficient of the soil around the polluted site and the change of the concentration and the type of pollutants contained in the soil; and injecting corresponding liquid medicine into the flexible lining according to actual needs to repair the vertical barrier until the construction of the vertical barrier is finished.

2. The method for monitoring the pollution site by combining the flexible bushing technology as claimed in claim 1, wherein the flexible bushing is arranged in an originally designed monitoring point during construction, a monitoring instrument and a sensor are placed in the flexible bushing, the soil condition around the pollution site is monitored in real time, the vertical barrier operation condition is analyzed, whether barrier local breakdown occurs or not is judged, and if pollutants are found, a medicament is injected into the flexible bushing for repairing.

3. The method as claimed in claim 1, wherein K is a permeability coefficient calculated from the rate of descent of the flexible liner and the pressure gauge reading.

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