CN109142157B

CN109142157B - Test earth and rockfill dam infiltration line cable

Info

Publication number: CN109142157B
Application number: CN201810770297.8A
Authority: CN
Inventors: 陈仁朋; 陈卓; 陆明; 刘惠斌; 王晨光
Original assignee: Hunan University
Current assignee: Hunan University
Priority date: 2018-07-13
Filing date: 2018-07-13
Publication date: 2021-08-24
Anticipated expiration: 2038-07-13
Also published as: CN109142157A

Abstract

The invention relates to water conservancy projects, in particular to a cable for testing an earth-rock dam infiltration line; the test earth and rockfill dam infiltration line cable sequentially comprises the following parts from inside to outside: the inner conductor layer is made of copper materials, the insulating layer is made of polytetrafluoroethylene, the outer conductor layer is of a copper open structure, and the outer sleeve layer is made of insulating waterproof materials. The sensitivity of the electromagnetic wave radiated when the cable is used for monitoring to the medium water can accurately and quickly capture the change of the water level. The invention can avoid the condition that the traditional dam saturation line monitoring device is greatly influenced by temperature and stress, can monitor the earth and rockfill dam saturation line with larger temperature difference and local stress, can realize long-term use due to the protection of the sheath, and is a safe, rapid and accurate earth and rockfill dam saturation line testing device.

Description

Test earth and rockfill dam infiltration line cable

Technical Field

The invention relates to water conservancy projects, in particular to a cable for testing an earth-rock dam infiltration line.

Background

The infiltration line is a life line of the safety of the earth-rock dam, the height of the infiltration line is directly related to the stability and safety of the dam body, and piping can be generated when the buried depth of the infiltration line is 0m, so that the dam break is directly caused. Therefore, monitoring the position of the saturation line is one of important contents for reservoir safety monitoring. The infiltration line is the intersection line of the surface of the infiltration water flow and the cross section of the earth-rock dam. The soil below the dam is in a saturated state, the weight of the particles is effective weight, and the particles are simultaneously acted by the osmotic force of the seepage water, so the height and the shape of the position of the seepage line in the dam have great influence on the stress of the dam, the shear strength of soil materials, the stability of a dam slope and the osmotic stability of the soil materials. The determination of the position is an important content of earth-rock dam seepage analysis and stability analysis, and how to effectively reduce the position of a saturation line is also a research topic in practical engineering.

At present, a method of embedding a piezometer tube or a vibrating wire type pressure gauge is generally adopted, the position of a water head at an embedding point of an instrument is calculated by utilizing the relation between pressure intensity and the water head in hydraulics, and finally, the shape and the change rule of a wetting line are deduced, but the error is large. Factors influencing the measurement error of the seepage line include the measurement error of the sensor installation depth H, the density value error of the seepage water, the gravity acceleration value error and the equipment performance (including the accuracy of temperature and air pressure compensation equipment and the like).

The earth mass is a three-phase system comprising air, soil particles and water. The dielectric constant of air is about 1, the dielectric constant of earth is in the range of 3-10, and the dielectric constant of water is about 80. The principle of TDR is to determine the information of mismatch by reflecting electromagnetic waves at the impedance mismatch of conductors, and the characteristic impedance of a medium is related to the geometric dimension of the conductors and the dielectric constant of the medium between the conductors. Therefore, in the soil-rock dam saturation line monitoring, the dielectric constant of the water-soil mixture below the saturation line is obviously different from that of the unsaturated soil at the upper part, and the reflection coefficient is calculated according to the formula

Wherein Z₁Is the characteristic impedance of saturated soil, Z₂The electromagnetic wave is obviously reflected at the position of the saturation line for the characteristic impedance of unsaturated soil, and the depth of the saturation line can be calculated according to a travel time method, so that the position change of the saturation line is monitored.

Disclosure of Invention

The invention aims to provide a cable for testing an earth and rockfill dam infiltration line, which solves the problems of inaccurate measurement and complex operation of a dam infiltration line.

The invention is realized by the following steps:

the utility model provides a test earth and rockfill dam infiltration line cable, test earth and rockfill dam infiltration line cable includes the inner conductor layer, and the outer parcel of inner conductor layer has the insulating layer, and the outer parcel of insulating layer has the overcoat layer, its characterized in that, install the outer conductor layer between insulating layer and the overcoat layer, take shape on the outer conductor layer or between the outer conductor layer and have the opening, the overcoat layer is made for insulating waterproof material. The opening may allow electromagnetic waves to radiate out. The size and number of the openings can be determined according to the requirement. The outer sleeve layer is made of insulating waterproof materials, so that water does not enter the cable, and electromagnetic waves can be radiated out of the cable without hindrance.

In a further improvement, the outer conductor layer is made of copper, and the opening extends along the length direction of the tested earth-rock dam wetting line cable; the inner conductor layer material is also copper.

In a further improvement, the opening is multiple.

In a further improvement, the number of the openings is three, and the openings are uniformly distributed on the test earth and rockfill dam wetting line cable and extend along the length direction of the test earth and rockfill dam wetting line cable.

In a further improvement, the openings of the outer conductor layer are filled with an insulating layer. The opening is filled with polytetrafluoroethylene (insulating layer), so that the strength of the cable can be ensured, and the service life is longer.

In a further improvement, the insulating layer is made of polytetrafluoroethylene.

In a further improvement, the insulating waterproof material is fluorinated ethylene propylene.

In a further improvement, the test earth and rockfill dam wetting line cable is vertically buried.

The invention has the beneficial effects that: sensitivity to medium water when utilizing this cable to monitor can accurately catch the change of water level fast for the life greatly increased of cable because the protection of sheath. The transmission of the electromagnetic wave is not influenced by external temperature or stress, and the test performance is relatively stable. In addition, the dam long-distance monitoring requirement is considered, the characteristic that the reflection waveform changes when electromagnetic waves propagate and radiate in the cable to meet a water body outside the sheath is utilized, the defect that the traditional TDR needs probe cooperation measurement is overcome, the application range of the traditional TDR is expanded to be a long distance from a short distance, and the monitoring cost is greatly reduced.

Drawings

FIG. 1 is a cross-sectional view of a test earth and rockfill dam saturation line cable provided by the present invention;

FIG. 2 is a schematic diagram of the electromagnetic wave radiation in the cable of the present invention;

fig. 3 is a schematic diagram of the use of the cable for testing the infiltration line of the earth and rockfill dam according to the present invention.

Reference numerals: 1. the device comprises an inner conductor layer 2, an insulating layer 3, an outer conductor layer 4, an outer sleeve layer 5, a TDR tester 6, a fixed end 7, a test earth-rock dam wetting line cable 8 and an opening.

Detailed Description

Fig. 1 shows a test earth and rockfill dam infiltration line cable, which sequentially comprises from inside to outside: the electromagnetic wave radiation-proof structure comprises an inner conductor layer, an insulating layer, an outer conductor layer and an outer sleeve layer, wherein the inner conductor layer is made of copper, the insulating layer is made of polytetrafluoroethylene, the outer conductor layer is of an open structure, and electromagnetic waves are allowed to radiate out through the open outer conductor layer; the outer conductor layer is made of copper, the outer conductor layer is provided with openings, and the size and the number of the openings are determined according to requirements; the opening of the outer conductor layer is filled with polytetrafluoroethylene, so that the strength of the cable can be ensured, and the service life is longer; the outer sleeve layer is made of an insulating waterproof material, so that water does not enter the cable, and electromagnetic waves can be radiated out of the cable without hindrance; fig. 3 is a schematic diagram showing the use of a test earth and rock dam wetting line cable, which mainly aims at an earth and rock dam in hydraulic engineering and is embedded and fixed at the bottom of the dam in the early stage of the construction of the earth and rock dam; in the embedding process, the vertical placement of the cable is ensured, because the position of the cable which is reflected represents the position of a wetting line, if the cable is bent in the vertical direction, the position judgment has errors; after the dam body is constructed, the cable is buried completely, and the cable is connected with a TDR signal transmitting device and can be used; the sensitivity to medium water when measuring by utilizing the test earth-rock dam infiltration line cable and the TDR instrument can accurately and quickly capture the change of the water level, and the service life of the cable is greatly prolonged due to the protection of the sheath. The transmission of the electromagnetic wave is not influenced by external temperature or stress, and the test performance is relatively stable. In addition, the requirement of long-distance monitoring of the dam is considered, the characteristic that the reflected waveform changes when electromagnetic waves propagate and radiate in the cable to meet a water body outside the sheath is utilized, the defect that the traditional TDR needs probe cooperation measurement is overcome, the application range of the traditional TDR is expanded to be a long distance from a short distance, and the testing cost is greatly reduced.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included therein.

Claims

1. A method for testing an earth and rockfill dam infiltration line is characterized by comprising the following steps:

firstly, burying and fixing a tested earth and rockfill dam wetting line cable at the dam bottom in the initial construction stage of the earth and rockfill dam; in the embedding process, the vertical placement of the test earth and rockfill dam wetting line cable is guaranteed, the test earth and rockfill dam wetting line cable comprises an inner conductor layer (1), an insulating layer (2) wraps the inner conductor layer (1), an outer sleeve layer (4) wraps the insulating layer (2), an outer conductor layer (3) is installed between the insulating layer (2) and the outer sleeve layer (4), an opening (8) is formed in the outer conductor layer (3) or between the outer conductor layers (3), and the outer sleeve layer (4) is made of an insulating waterproof material; the outer conductor layer (3) is made of copper, and the opening (8) extends along the length direction of the cable for testing the earth-rock dam wetting line; the material of the inner conductor layer (1) is also copper; the three openings (8) are uniformly distributed on the tested earth and rockfill dam wetting line cable and extend along the length direction of the tested earth and rockfill dam wetting line cable; the opening of the outer conductor layer (3) is filled with an insulating layer (2);

step two, completing the burying of the tested earth and rockfill dam wetting line cable along with the completion of the dam body construction, wherein the tested earth and rockfill dam wetting line cable is connected with a TDR signal transmitting device;

and step three, rapidly capturing the change of the water level by utilizing the sensitivity of the tested earth-rock dam wetting line cable and a TDR instrument to the medium water during measurement, wherein the position of the cable which is reflected represents the position of the wetting line.

2. The method of testing an earth and rockfill dam wetline of claim 1, wherein: the insulating layer (2) is made of polytetrafluoroethylene.

3. The method of testing an earth and rockfill dam wetline of claim 1, wherein: the insulating waterproof material is fluorinated ethylene propylene.