Surface barrier structure for dam termite prevention

Abstract

The utility model relates to a surface barrier structure for preventing termites of a dam. The dam comprises a dam body, a protection slope, drainage prisms and infiltration lines. The surface barrier structure comprises an anti-termite layer which is arranged between a protection slope and a dam body and comprises a liquid-doped soil layer and a water-resisting layer from outside to inside; the water conveying system comprises a water conveying main pipe and water conveying branch pipes, the water conveying branch pipes are arranged at different elevations of the liquid-doped soil layer, the upper end of the water conveying main pipe is used for inputting doped liquid, and the lower end of the water conveying main pipe is connected with the water conveying branch pipes at different elevations; by pre-burying the water conveying pipeline, the process of increasing the salt (chemical) content of soil can be extended to the time after the dam body is completed, construction is easy and convenient, the influence on dam body construction is small, the construction period is shortened, the construction quality of the barrier structure is guaranteed, and the construction cost is reduced; the salt (pesticide) content of soil can be monitored in real time in the operation and maintenance period, salt (pesticide) water conveying is carried out according to actual conditions, the protection effect of the barrier structure is ensured, and maintenance is convenient; the water-resisting layer in the anti-termite layer is made of clay, combination of soil layers is facilitated, and stability of the dam slope is guaranteed.

Description

Technical Field

[0001] This utility model relates to the field of termite control technology in water conservancy and hydropower projects, and in particular to a surface barrier structure for termite prevention in dams. Background Technology

[0002] Subterranean termites pose a significant threat to dam safety. They alter the soil structure of dams by digging tunnels inside, thus affecting their stability and safety. The presence of termite nests can lead to seepage, piping, and other hazards, and in severe cases, may even cause dam collapse.

[0003] To effectively control soil-dwelling termites, saline-soil or chemical-treated soil barrier technology has emerged. This technology involves adding a certain amount of salt or chemical (hereinafter referred to as the incorporation solution) to specific areas of the dam to form a termite-resistant barrier. The barrier structure alters the soil environment, preventing termites from surviving and reproducing, thus achieving termite control. However, traditional dam barrier construction has certain drawbacks. First, the incorporation solution barrier requires salting, spraying salt water, or chemical solution onto the soil surface above the seepage line, which consumes significant funds, manpower, and resources, resulting in high construction costs and a substantial impact on the project schedule. Second, the dam barrier structure requires high construction quality; poor quality control may affect the protective effect. Finally, the barrier structure requires regular inspections for maintenance, and repairs require specialized equipment, which is difficult and may necessitate increasing the soil salinity or re-spraying the chemical solution to maintain its protective effect, making maintenance difficult and costly. Therefore, it is necessary to propose a dam surface barrier structure that is easy to construct, saves on costs and time, and facilitates subsequent maintenance.

[0004] Therefore, this case is brought. Utility Model Content

[0005] The purpose of this utility model is to provide a surface barrier structure for termite prevention in dams, which has the advantages of simple construction, safety and reliability, low cost, time saving, easy quality control and convenient maintenance.

[0006] To achieve the above objectives, the technical solution of this utility model is as follows:

[0007] A surface barrier structure for termite prevention in dams, the dam including a dam body, a slope protection, a seepage-proof layer, a drainage prism and a seepage line, the slope protection including an upstream slope protection and a downstream slope protection respectively set on both sides of the dam body, the seepage-proof layer and the seepage line located in the dam body, and the drainage prism set at the dam toe below the downstream slope protection of the dam body;

[0008] The surface barrier structure includes:

[0009] The termite-proof layer is set between the slope protection and the dam body. From the outside to the inside, it includes a liquid-mixed soil layer and a water-proof layer. The liquid-mixed soil layer is set above the saturation line and extends longitudinally from the upstream slope protection through the top of the dam body and the downstream slope protection to the drainage prism. The water-proof layer is set above the saturation line and extends longitudinally from the top of the dam body to the toe of the downstream slope protection.

[0010] The water conveyance system includes a main water conveyance pipe and several branch water conveyance pipes arranged at different elevations of the mixed soil layer. Several outlet holes are opened on the pipe wall. The upper end of the main water conveyance pipe is used to input the mixed liquid, and the lower end is connected to the branch water conveyance pipes at different elevations. The main water conveyance pipe is equipped with a main pipe maintenance valve and a main pipe control valve. The end of the branch water conveyance pipe connected to the main water conveyance pipe is equipped with a branch pipe control valve.

[0011] Furthermore, the termite-proof layer includes several monitoring devices installed in the liquid-mixed soil layer for monitoring the concentration of the mixed liquid in the liquid-mixed soil layer; the monitoring devices are pre-embedded devices and / or insertion devices.

[0012] Furthermore, the waterproof layer is made of clay.

[0013] Furthermore, the water supply branch pipe is provided with geotextile and steel wire, with the steel wire wrapped around the surface of the geotextile to firmly wrap the water supply branch pipe.

[0014] Furthermore, a pre-installed pressurization pipe is provided on the main water supply pipe.

[0015] Furthermore, water conveyance branch pipes at adjacent different elevations are connected; and / or the water conveyance branch pipe located on the upstream slope is connected to the water conveyance branch pipe at the top of the dam.

[0016] Furthermore, valve chambers are provided at the locations of the main maintenance valve, the reserved pressurization pipe, the main control valve, and the branch control valve. The valve chambers are made of finished stainless steel and have an openable and closable cover plate on top. The valve chambers are hidden below the ground surface.

[0017] Furthermore, the water supply system includes a submersible pump, a water supply pipe, a mixer, and a water storage tank. The water storage tank is located at the highest point of the dam and is connected to the upper end of the main water supply pipe. The water storage tank is used to store the admixture. The submersible pump is located on the upstream slope and is used to transport water from the reservoir to the water storage tank through the water supply pipe. The mixer is used to promote the uniform mixing of the admixture in the water storage tank.

[0018] And / or the water supply system adopts a mobile liquid storage vehicle, which is used to store the mixed liquid and can be connected to the main water supply pipe.

[0019] Furthermore, the water storage tank is made of cast-in-place concrete or prefabricated stainless steel, with an openable and closable cover on the top of the tank, and ladders or steps inside and outside the tank.

[0020] The advantages of this utility model are:

[0021] 1) Simple construction, time-saving and easy quality control: By setting a salt (medicated) soil layer (i.e., a liquid-mixed soil layer; when the mixed liquid is salt, it can be called a salt soil layer; when the mixed liquid is a medicine, it can be called a medicine soil layer) and a water-proof layer on the surface of the earth-rock dam, and pre-burying water pipelines in the salt (medicated) soil layer, and burying water supply equipment upstream of the earth-rock dam and on the side of the mountain, the process of increasing the soil salinity (medicated) content of the salt (medicated) soil layer can be extended to after the dam is completed. The overall construction is simple, has little impact on the main dam construction, saves construction time, and the soil salinity (medicated) content index can be strictly controlled through monitoring equipment during the later process of salt (medicated) water supply, ensuring the construction quality of the salt (medicated) soil barrier;

[0022] 2) Low construction cost: The water supply and water conveyance systems included in this plan have low costs. The process of increasing the soil salinity (chemical) content of the saline (chemical) soil layer is extended to after the dam body is completed. The saline (chemical) water can flow to the saline (chemical) soil layer by gravity. Compared with the traditional situation where the saline (chemical) soil barrier is implemented simultaneously with the main dam body, it greatly reduces labor and machinery costs and lowers construction costs.

[0023] 3) Convenient post-maintenance: During the operation and maintenance of the reservoir, the salt (chemical) content of the saline (chemical) soil layer is monitored in real time by monitoring equipment. For defective areas with significantly reduced soil salt (chemical) content, the water supply and transmission system can be activated, and targeted salt (chemical) water can be delivered to the defective saline (chemical) soil layer by adjusting the opening and closing of the control valve, thereby increasing the soil salt (chemical) content in the defective area, ensuring the protective effect of the saline (chemical) soil barrier, and making overall maintenance convenient without the need for secondary excavation and repair, with minimal impact on the dam body;

[0024] 4) Safe and reliable: The waterproof layer in the termite-proof layer described in this plan is made of clay with low permeability and is implemented above the saturation line. This does not affect the seepage prevention principle of "upper interception and lower drainage" of the earth-rock dam, and also ensures the stability of the contact surface between the waterproof layer and the adjacent salt (medicinal) soil layer and the dam body, avoiding slope instability caused by the formation of unfavorable structural surfaces. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the planar layout of the surface barrier structure for termite prevention on the dam in Example 1;

[0026] Figure 2 yes Figure 1 A-A sectional view;

[0027] Figure 3 yes Figure 1 Detailed drawing A;

[0028] Figure 4 yes Figure 2 Detailed drawing B;

[0029] Figure 5 yes Figure 3 Schematic diagram of B-B section;

[0030] Figure 6 yes Figure 5 Detailed drawing C;

[0031] Label Explanation:

[0032] 1. Dam; 11. Upstream slope protection; 12. Downstream slope protection; 13. Dam crest; 14. Dam body; 15. Impermeable layer; 16. Drainage prism; 17. Seepage line;

[0033] 2. Water supply system; 21. Submersible pump; 22. Water supply pipe; 23. Water storage tank; 24. Mixer; 25. Additive solution;

[0034] 3. Water supply system; 31. Main water supply pipe; 32. Branch water supply pipe; 32a. Permeable perforated pipe; 32b. Geotextile; 32c. Steel wire; 33. Main pipe maintenance valve; 34. Main pipe control valve; 35. Reserved pressurization pipe; 36. Branch pipe control valve; 37. Valve chamber;

[0035] 4. Anti-termite layer; 41. Liquid-mixed soil layer; 42. Waterproof layer; 43. Monitoring equipment. Detailed Implementation

[0036] The present invention will be further described in detail below with reference to the embodiments. It should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer" etc. indicated by the accompanying drawings are only for the convenience of describing the present invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0037] Example 1

[0038] like Figures 1 to 6 As shown in the figure, this embodiment proposes a surface barrier structure for termite prevention on dams, which has the advantages of simple construction, safety and reliability, low cost, time saving, easy quality control, and convenient maintenance. This surface barrier structure is installed on the dam 1 and includes a water supply system 2, a water conveyance system 3, and a termite-proof layer 4.

[0039] like Figure 2As shown, dam 1 has the same structure as existing dams that adopt the "upper interception, lower drainage" seepage prevention principle, including a slope protection, dam body 14, seepage prevention layer 15, drainage prism 16, and seepage line 17. The slope protection includes an upstream slope protection 11 and a downstream slope protection 12 respectively set on both sides of the dam body 14. The seepage prevention layer 15 and seepage line 17 are located inside the dam body, and the drainage prism 16 is set at the dam toe below the downstream slope protection 12 of the dam body 14. The seepage line 17 is the intersection line between the free water surface formed by water seeping from the water-facing side of the earthen dam (or earthen dike) downstream through the dam body and the cross-section of the dam body.

[0040] like Figure 1 and Figure 3 As shown, the water supply system 2 includes a submersible pump 21, a water supply pipe 22, a water storage tank 23, a mixer 24, and an additive solution 25. The water storage tank 23 is located on the dam crest 13, and the submersible pump 21 is located on the upstream slope 11 of the dam 1. It can transport water from the reservoir to the water storage tank 23 via the water supply pipe 22. The water storage tank 23 is connected to the water conveyance system 3 on the side of the dam 1 to transport the additive solution 25 to the termite-proof layer 4. The mixer 24 inside the water storage tank 23 promotes better dissolution of the additive solution 25 (e.g., mixing salt and water, or mixing chemicals and water). Alternatively, the mixer 24 can be manually operated externally, reducing the need for internal machinery and related electrical equipment. Taking brine as an example, water in the water storage tank 23 needs to be pumped into the tank first by the submersible pump 21. After adding salt, the mixer 24 inside the water storage tank 23 is activated to promote better dissolution of the brine. Water supply pipe 22 can be buried underground along one side of the earth-rock dam 1 into the water storage tank 23.

[0041] The termite-proof layer 4 is set between the slope protection and the dam body 14, and includes a liquid-mixed soil layer 41, a water-proof layer 42 and a monitoring device 43. The water-proof layer 42 is set between the dam body 14 and the liquid-mixed soil layer 41, and the liquid-mixed soil layer 41 is set between the water-proof layer 42 and the slope protection.

[0042] like Figure 2 As shown, the liquid-mixed soil layer 41 is positioned above the phreatic line 17, extending longitudinally from the upstream slope 11 through the dam crest 13 and downstream slope 12 to the drainage prism 16. The impermeable layer 42 is positioned deeper within the dam body 14 and closely adjacent to the liquid-mixed soil layer 41. The impermeable layer 42 prevents the mixed liquid 25 seeping from the water supply branch pipe 32 from flowing into other soil layers deep within the dam body 14. Simultaneously, to avoid affecting the "upper interception, lower drainage" seepage prevention principle of the dam 1, the impermeable layer 42 is positioned above the phreatic line, with a shorter longitudinal range than the liquid-mixed soil layer 41, extending from the dam crest 13 to the downstream slope 12 near the dam toe. The monitoring device 43 is used to monitor the concentration of the mixed liquid in the liquid-mixed soil layer 41 to better control the soil mixed liquid concentration index, thereby achieving a good termite protection effect.

[0043] Preferably, the impermeable layer 42 can be made of clay with low permeability to ensure the stability of the contact surface between the impermeable layer 42 and the mixed soil layer 41 and the dam body 14, so as to prevent the formation of unfavorable structural surfaces that could lead to slope instability. Meanwhile, the monitoring equipment 43 can be a pre-embedded device, installed in a relatively loose soil layer with vegetation on the surface, or other insertable devices can be used to monitor soil salinity during the operation and maintenance period.

[0044] The submersible pump 21, the mixer 24, and the pre-embedded monitoring equipment 43 should all be equipped with power distribution to facilitate equipment operation.

[0045] The water supply system 3 includes a main water supply pipe 31, branch water supply pipes 32, a main pipe maintenance valve 33, a main pipe control valve 34, a reserved pressurization pipe 35, a branch pipe control valve 36, and a valve chamber 37. Multiple branch water supply pipes 32 are arranged at different elevations within the mixed soil layer 41. The main water supply pipe 31 connects to a water storage tank 23 at the top and to branch water supply pipes 32 at different elevations at the bottom. The main water supply pipe 31 is equipped with a main pipe maintenance valve 33, a reserved pressurization pipe 35, and a main pipe control valve 34 along its length. The branch pipe control valve 36 of each branch water supply pipe 32 is located at its connection point to the main water supply pipe 31. Valve chambers 37 should be provided at the locations of the main pipe maintenance valve 33, the reserved pressurization pipe 35, the main pipe control valve 34, and the branch pipe control valve 36 to conceal the valves or reserved pipelines below the ground surface, thus not affecting the normal operation and maintenance of the project or its aesthetics. Because of its small size, valve chamber 37 can be made of precast stainless steel for easy construction. At the same time, valve chamber 37 is equipped with a cover plate on top for easy opening and closing operations.

[0046] like Figure 6 As shown, the water supply branch pipe 32 adopts the structure of a permeable perforated pipe 32a, with geotextile 32b and steel wire 32c on the outside. The steel wire 32c is wound around the surface of the geotextile 32b, firmly wrapping the geotextile 32b around the permeable perforated pipe 32a. The permeable perforated pipe 32a can ensure that the admixture 25 permeates into the admixture soil layer 41, and the geotextile 32b can prevent soil particles in the admixture soil layer 41 from entering the permeable perforated pipe 32 and causing blockage.

[0047] With the above design, the mixed liquid 25 in the water storage tank 23 can flow by gravity to the main water supply pipe 31 and the branch water supply pipe 32, or the mixed liquid 25 can be pressurized to the main water supply pipe 31 and the branch water supply pipe 32 by external equipment through the reserved pressurization pipe 35.

[0048] Preferably, the water storage tank 23 can be made of cast-in-place concrete or precast stainless steel. A cover plate is provided on the top of the tank for easy opening and closing. Ladders or steps can be installed inside and outside the tank for manual operation and maintenance. Waterproofing treatment should be applied to the connection points between the water supply pipe 22, the main water supply pipe 31, and the water storage tank 23 to prevent leakage of the admixture 25. T-junctions should be used at the branch points of the main water supply pipe 31 and at the connection points between the main water supply pipe 31 and the branch pipe 32 to ensure proper connection and prevent leakage of the admixture 25.

[0049] Meanwhile, the water delivery branch pipes 32 can be connected between adjacent sections at different elevations, and the number of branch pipe control valves 36 can be adjusted accordingly to achieve flexible control of the mixed soil layer 41 over a wider area, making operation easier. On the upstream slope 11 side of the dam, where control valves are inconvenient to implement, a small number of water delivery branch pipes 32 can be connected to the water delivery branch pipe 32 at the dam crest 13. Furthermore, the main water delivery pipe 31 and the branch pipes 32 can be made of PE pipe to accommodate deformation caused by soil settlement.

[0050] During the installation process, equipment such as water supply branch pipe 32 and branch pipe control valve 36 that are constructed in conjunction with the dam 1 should be pre-embedded during the construction of the dam 1. Equipment such as water supply system 2 that are not constructed in conjunction with the dam 1 can be installed after the dam 1 is completed. The process of conveying the admixture 25 into the admixture soil layer 41 can also be carried out after the dam body 14 is completed, thereby reducing the impact on the main construction of the dam 1, saving construction time, and during the later process of conveying the admixture 25, the soil admixture concentration index can be strictly controlled by the monitoring equipment 43 to ensure the construction quality of the admixture soil layer 41.

[0051] This embodiment also proposes an implementation method for the surface barrier structure for termite prevention described above. By pre-burying a water conveyance pipe within the liquid-mixed soil layer 41 on the surface of the dam 1, the process of increasing the concentration of the mixed liquid in the mixed soil layer 41 can be delayed until after the dam is completed. This minimizes the impact on the main dam construction, saves construction time, and reduces construction costs. Simultaneously, the concentration of the mixed liquid at defective locations can be specifically increased during the reservoir's operation and maintenance period to ensure the protective effect of the barrier structure. Secondary excavation and repair are unnecessary, minimizing the impact on the dam and ensuring its safety and stability. The implementation method includes the following steps:

[0052] S1. During the construction period of dam 1, concealed devices such as main water supply pipe 31, branch water supply pipe 32, main pipe maintenance valve 33, main pipe control valve 34, reserved pressurization pipe 35, branch pipe control valve 36 and testing equipment 43 are pre-embedded in the dam body.

[0053] During the construction period of dam 1, external devices such as water supply system 2 will be implemented simultaneously as appropriate.

[0054] S3. After the dam 1 is completed, the admixture liquid 25 is promptly transported to the admixture soil layer 41 through the water supply system 2 and the water conveyance system 3 until the concentration of the admixture liquid in the admixture soil layer 41 reaches the termite control requirements.

[0055] S4. During operation, the concentration of the admixture in the admixture soil layer 41 is monitored periodically by the monitoring equipment 43. When the concentration of the admixture in the admixture soil layer is lower than the termite control requirements, the water supply system 2 and the water delivery system 3 are turned on. The admixture is then delivered to the defective admixture soil layer 41 in a targeted manner by adjusting the opening and closing of the regulating pipe control valve 34 and the branch pipe control valve 36, thereby increasing the concentration of the admixture in the defective parts and ensuring the protective effect of the barrier.

[0056] Example 2

[0057] The principle of this embodiment is basically similar to that of Embodiment 1, except that the water supply system 2 in this embodiment uses a mobile liquid storage vehicle, while the submersible pump 21, water supply pipe 22, water storage tank 23, and mixer 24 in Embodiment 1 are not installed. The liquid storage vehicle is used to store the added liquid. When liquid replenishment is needed, the mobile vehicle containing brine or medicine is driven to the vicinity of the dam top, and the brine or medicine is transported to the termite-proof layer 4 through the connecting water supply main pipe 31.

[0058] Example 3

[0059] The principle of this embodiment is basically similar to that of embodiment 1. The difference is that the water supply system 2 in this embodiment also includes a mobile liquid storage vehicle. The liquid storage vehicle is used to store the mixed liquid. When the water storage tank 23 is unavailable but needs to be replenished (such as during operation and maintenance), the mobile vehicle containing brine or medicine is driven to the vicinity of the dam top. It can be connected to the main water supply pipe 31 through the reserved pressurization pipe 35, or the connection between the main water supply pipe 31 and the water storage tank 23 can be disconnected first, and then the output end of the vehicle can be connected to the main water supply pipe 31 to finally deliver the brine or medicine to the termite-proof layer 4.

[0060] The above embodiments are only used to explain the concept of this utility model, and are not intended to limit the protection of this utility model. Any non-substantial modifications made to this utility model using this concept should fall within the protection scope of this utility model.

Claims

1. A surface barrier structure for embankment termite prevention, the embankment comprising an embankment body, a slope protection, an impervious layer, a drainage prism and a saturation line, the slope protection comprising an upstream slope protection and a downstream slope protection respectively arranged on two sides of the embankment body, the impervious layer and the saturation line being located in the embankment body, the drainage prism being arranged at a dam toe below the downstream slope protection of the embankment body; characterized in that the surface barrier structure comprising: a termite prevention layer arranged between the slope protection and the embankment body, comprising a liquid-mixed soil layer and a water-resisting layer from outside to inside, the liquid-mixed soil layer being arranged above the saturation line and longitudinally from the upstream slope protection through the top of the embankment body to the downstream slope protection and to the drainage prism, the water-resisting layer being arranged above the saturation line and longitudinally from the top of the embankment body to the foot of the downstream slope protection; a water delivery system comprising a water delivery main pipe and water delivery branch pipes, the water delivery branch pipes being arranged in different elevations of the liquid-mixed soil layer, pipe walls of the water delivery branch pipes being provided with a plurality of liquid outlet holes, the water delivery main pipe being used for inputting liquid-mixed liquid at an upper end thereof and being connected to the water delivery branch pipes at different elevations, the water delivery main pipe being provided with a main pipe maintenance valve and a main pipe control valve along a line, and the water delivery branch pipes being provided with branch pipe control valves at end portions of sides connected to the water delivery main pipe.

2. A surface barrier structure for dam termite prevention as claimed in claim 1, wherein, The termite prevention layer comprises a plurality of monitoring devices arranged in the liquid-mixed soil layer for monitoring concentration of the liquid-mixed liquid in the liquid-mixed soil layer.

3. A surface barrier structure for dam termite prevention as defined in claim 1, wherein, The water-resisting layer is made of clay.

4. A surface barrier structure for dam termite prevention as defined in claim 1, wherein, The water delivery branch pipes are externally provided with geotextiles and steel wires, the steel wires being wound on surfaces of the geotextiles to tightly wrap the water delivery branch pipes with the geotextiles.

5. A surface barrier structure for dam termite prevention as defined in claim 1, wherein, The water delivery main pipe is provided with a reserved pressurizing pipe.

6. A surface barrier structure for dam termite prevention according to claim 1, wherein, The water delivery branch pipes at adjacent different elevations are connected to each other; and / or the water delivery branch pipes located on the upstream slope protection side are connected to the water delivery branch pipes at the top of the embankment body.

7. A surface barrier structure for dam termite prevention as defined in claim 5, wherein, The positions of the main pipe maintenance valve, the reserved pressurizing pipe, the main pipe control valve and the branch pipe control valves are provided with valve chambers, the valve chambers are made of finished stainless steel materials, and are provided with openable and closable cover plates at top portions, and the valve chambers are hidden below the ground surface.

8. The surface barrier structure for embankment termite prevention according to claim 1, further comprising a water supply system. The water supply system comprises a submersible pump, a water supply pipe, a stirrer and a water storage tank, the water storage tank being arranged at the highest position of the embankment body and being connected to the upper end of the water delivery main pipe, the water storage tank being used for storing the liquid-mixed liquid, the submersible pump being arranged on the upstream slope protection and being used for delivering water in a reservoir to the water storage tank through the water supply pipe, and the stirrer being used for promoting uniform mixing of the liquid-mixed liquid in the water storage tank. The water supply system adopts a movable liquid storage vehicle, the liquid storage vehicle being used for storing the liquid-mixed liquid and being connectable to the upper end of the water delivery main pipe. The water storage tank is made of cast-in-situ concrete or a finished stainless steel tank body, the tank body is provided with an openable and closable cover plate at a top portion, and a ladder or steps are arranged outside and inside the tank body.

9. A surface barrier structure for dam termite prevention as defined in claim 8, wherein, The monitoring devices adopt pre-embedded devices and / or plug-in devices.

10. A surface barrier structure for dam termite prevention as defined in claim 2, wherein, ​

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