RU2393290C2 - Method for monitoring safety of earth dam and device for its implementation - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: method for monitoring safety of earth dams includes installation of basic piles and registration of ground displacements. Rope is pulled between piles and is enclosed into brittle lime-cement lining - train, which is tightly joined to surface of dam slope ground. Ground displacements are registered by variation of rope length with the help of light and sound alarm, besides area of ground displacements is determined by cracks that occurred on lining.

EFFECT: invention makes it possible to continuously monitor safety of earth dam faces and to improve accuracy of landslip are detection.

1 cl, 5 dwg

Description

The invention relates to dam engineering and can be used to control the occurrence and propagation of deformations in the body of a soil dam, the initial shifts and movements caused by the loss of stability of the slopes of the dam. It can also be used to monitor the status of slopes of road embankments and sides of quarries, pits and various bulk structures used in hydraulic engineering.

In the method, a groove in the soil is arranged on the surface of the controlled slope throughout the entire area that requires continuous monitoring.

At the beginning and end of the groove, piles are driven into the pile with a dip below the freezing mark. A rod of wire, steel rod or fiberglass is pulled between the piles. One end of the rod is fixed motionless in the pile, and the other through the spring tensioner, which ensures its movement under various influences by changing its length.

After this, the groove with the rod located in it is filled with lime-cement mortar until it is completely in contact with the slope soil. In this case, the core is preliminarily coated with bitumen, so as to provide the possibility of its independent movement inside the lime-cement filling. The system of a movable rod and brittle material filling the grooves forms a loop, which is placed strictly rectilinearly in any plane of the slope of the soil dam, in the zone covering the area of the occurrence of deformations in case of buckling. Depending on the design of the slope of the soil dam, the planned location, height and material, the length of the loop can be hundreds of meters, that is, it is possible to control the slope over a long distance and be located in any direction.

Monitoring the state of the slope of the soil dam is carried out as follows: when initial deformations occur in the soil of the slope, the pressure from it is transmitted to the rod and changes its length, which is recorded by a special device located in the tubular pile, including closing the contacts of the light or sound signaling device. The very place of occurrence of ultimate strains in the slope soil is determined by the cracks of the brittle filler of the loop groove when viewed on site.

Thus, the invention has the features of a method and device. The method is characterized in that the present invention allows continuous monitoring of the slope for any type of deformation thereof: decompression, heaving, creeping, cracking and other manifestations.

The device allows you to determine the site of the occurrence of deformations, its boundaries and the nature of the change over time (increase, decay of deformations or stabilization).

The technical solution relates to dam engineering, is intended to control the occurrence and propagation of delamination, soil shear in the dam body, the development of cracks and creep, heaving and subsidence.

A known method of controlling the stability of slopes by ed. testimonial. USSR No. 1788239 A1, class E21C 39/00, publ. in BI No. 2, 1993. In this method, the structure of the slope array is studied and blocks separated by potentially dangerous weakening surfaces of the array are outlined. Within the boundaries of each block, reference points are established, which are seamlessly connected with the blocks. Inductive-frequency sensors oriented in the direction of the expected shift are placed between adjacent reference points. The lengthening of the rod of the inductive-frequency sensor causes an adequate change in the frequency of the electric current recorded by the frequency meter and a special device. Frequency is supplied via cable to the control room; the system requires preliminary calibration.

This method requires the preliminary selection of potentially dangerous weakening surfaces, which may not coincide with the actual ones, which leads to unreliable results. In addition, calibration of several sensors is required, laying of cable lines from them, which significantly increases the cost of the control system.

The closest in technological essence and the totality of essential features is the device described in ed. testimonial. USSR No. 168891 AS, cl. Е21С 39/00, 1999. In this device for measuring deformations of a rock mass, two reference points are installed, connected by a measuring rod in the direction of the expected displacement of the rocks. The measuring rod is connected to a transducer of angular rotations into linear movements of the frames relative to each other. The reading device contains a complex system for recording pulses for transmitting information over a wired line or through a radio transmitting device to a control center, where data on the movement of rocks is processed.

As in the previous case, the placement of benchmarks is carried out in the obvious direction of rock displacement. To ensure the operation of the device requires sophisticated equipment and cable lines with a control room.

The device does not allow to monitor the formation of deformations arising in different planes, including heaving and softening.

A known method for determining the parameters of the stratification of rocks in the array and a device for its implementation by ed. testimonial. RF RU No. 2248446 C1, cl. E21C 39/00 2004, publ. in BI No. 8, 2005. The method includes drilling wells and installing signal lines in them in the form filled with a hardening mass, which, after hardening, forms brittle electrically conductive rods rigidly adhered to the walls of the wells. When the rock mass is stratified, the rods are destroyed or experience deformations, which are recorded by a change in the electrical resistance of the installed electrode from each level of deformation control in the well and displayed by the conductor to the surface with connection to the recording equipment. The wall of the well along the entire length and to the base is covered with a dielectric to isolate the conductive rod from the ground. This method has several disadvantages, the main of which are as follows:

- it is used to monitor the condition of the rock mass and the occurrence of horizontal cracks, the accuracy of which depends on the number of electrodes placed vertically;

- when the rocks are shifted along a plane perpendicular to the direction of the wells, the dielectric is cut off and the groundwater penetrates into the cavity of the shell completely violating the electrical resistance of the entire system, as a result of which it is not possible to establish the location of the shear horizon;

- the method requires the installation of a large number of wells in a controlled array, since the layering of the array in plan is not known in advance, which increases the cost of its application, including due to the large volume of cable laying;

- cohesive (clay, loam) and incoherent (sand, sandy loam) soils from which the slopes of soil dams are made, undergo deformation as a result of freezing and thawing, which can destroy the brittle dielectric shell of the rods and disrupt the operation of the device, which at the same time does not to violation of the stability of the slope. Therefore, the recommended application of this method for monitoring the state of a hydroelectric power station cannot be recognized as permissible, especially since wells can be in the filtration zone, that is, subjected to corrosive effects of water.

In general, the described device is laborious to manufacture, difficulties arise in determining the reliability of the information. In addition, the change in the electrical resistance of the rods should be calibrated at the test bench to obtain reliable communication with the arising voltages in the array.

The method developed and proposed in the application is implemented using the device as follows.

On the lower slope 1 (Fig. 1) of the soil dam, a straight groove 2 is laid, with a depth exceeding the thickness of the plant soil by 10-20 cm. The length of the groove corresponds to the length of the controlled section of the dam. At the beginning and end of the groove, tubular piles 3 and 4 are hammered to a mark exceeding the freezing depth by 0.5 ... 1.0 m. Between the piles along the bottom of the groove is a steel wire 5 (pre-stabilized cable length, fiberglass bundle, etc. )

One end of the cable is fixed motionless in the right pile 4, and the other through the spring tensioner in the left pile 3. The cable is covered with bitumen or synthetic insulation that prevents corrosion along its entire length.

After that, the groove, together with the cable located in it, is filled with cement-lime mortar 6 (Fig.2) in a spacer with the walls of the groove in the ground. Filling the groove with the solution should be planned along the surface of the slope to prevent erosion by rainfall. To increase the connection with the slope soil along the bottom of the groove before laying the mortar, steel pins 7 are clogged with a length of 1.0 ... 1.5 m.

The formation of soil motions on the lower slope of the soil dam is preceded by the emergence of slip planes and the loss of stability of the soil mass 8, limited by these surfaces. The soil pressure on the groove portion filled with the hardened solution can be considered as an unevenly distributed load 9 (Fig. 3) on the beam with pinched ends. Under the influence of this load, bending moments arise in the beam with a maximum value in its middle 10 and in places of conditional jamming 11, 12. As a result of the action of bending moments and insufficient strength of the filling material, cracks 13 arise in it, which limit the place of the landslide that arose or its other deformations.

In the left pile is a device that records the change in the length of the cable, shown in sections 4, 5. Before filling the groove with a solution, the minimum change 14 of the cable length is determined, caused by moving it to the maximum permissible amount of soil movement in the direction perpendicular to the axis of the cable.

The device that records the change in the length of the cable includes a measuring washer 15, mounted on the rod 16 and forming, together with the fixed face 17, a measuring gap 14 and the contacts of the light-sound alarm switch 18. With a large tension of the cable due to the movement of the soil 8 (figure 2) on the downhill slope, the contacts of the switch close and close the electric circuit to a light and sound signal. The bitumen insulation of the cable 19 must be sufficient so that it does not adhere to the filling material of the groove.

Having received a signal about a change in the length of the cable, the dam surveyor establishes the place of occurrence of the landslide and takes measures to prevent an emergency breakthrough of the structure.

With daily walk around the structure along the measuring gap, observations can be made of the movement of the cable, which characterizes the accumulation of deformations in the slope of the dam. At high altitude or length of the dam, several monitoring lines are installed.

The proposed method and device for monitoring the safety of soil dams satisfies the following conditions:

- can record the place of occurrence of ultimate deformations in the soil dam both over the entire length and in height from the sole to the crest;

- monitoring the state of the slope should be carried out continuously and at any time of the year with instant signaling about the occurrence of any very slight deformations;

- the place of occurrence of deformations is determined with sufficient accuracy for repair work;

- the monitoring device is not laborious to manufacture, does not contain non-ferrous metals and expensive products such as electric cables, electronic elements, etc .;

- the device can function independently of the power supply of the facility and allow the transmission of information over long distances;

- the device is available for use by persons who do not have a special education;

- the device is restored with minimal cost after the next operation.

Claims (2)

1. A method for monitoring the safety of soil dams, including the installation of basic piles and registration of soil displacements, characterized in that a cable is pulled between the piles and enclosed in a brittle lime-cement cladding-plume closely connected to the surface of the slope of the dam, and soil displacements are recorded by changing the length of the cable using light and sound signaling, and the place of soil displacements is set along the cracks that occur on the lining. 2. A device for monitoring the safety of soil dams, containing a device for measuring the displacement of the soil and comparing it with critical values, characterized in that the device for measuring the displacement of the soil is made in the form of a cable enclosed in a brittle lime-cement cladding-loop, laid in a straight groove, with a depth exceeding the thickness of the plant soil by 10-20 cm, and the cable is stretched between two piles hammered at the beginning and end of the groove to a mark exceeding the freezing depth by 0.5-1.0 m, at The cable is equipped with a spring tensioner, made in the form of a measuring washer, mounted on the rod with the formation of a measuring gap together with the stationary face and the contacts of the light-sound alarm switch.

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