Methods for monitoring settlement of upstream rockfill area of ​​existing earth-core and asphalt-core rockfill dams

Abstract

This invention provides a method for monitoring settlement in the upstream rockfill area of ​​an existing earth-core and asphalt-walled rockfill dam. A flexible inclinometer, settlement steel pipe, and prism are systematically deployed in the upstream rockfill area. The flexible inclinometer is vertically drilled to obtain horizontal displacements at different elevations and locations within the upstream rockfill area. The prism is used to obtain settlement values ​​at the bottom measuring points of the settlement steel pipe, thus forming a relatively complete settlement monitoring technology scheme for the upstream rockfill area of ​​an existing dam. This method is simple to implement and can obtain information on the internal deformation of the upstream rockfill area during the impoundment and operation of an existing dam, which is of great significance for analyzing and evaluating the operational safety of the existing dam.

Description

Technical Field

[0001] This invention relates to the technical field of safety monitoring of earth-rock dams, specifically to a method for monitoring settlement in the upstream rockfill area of ​​an existing earth-core rockfill dam. Background Technology

[0002] In recent years, with the rapid development of hydropower dam construction technology in China, a large number of earth-rock dams have been completed and put into operation. After impoundment, the upstream rockfill area of ​​the dam will undergo wetting deformation due to the influence of reservoir water. Excessive deformation may affect the stability of the dam body and slope, and affect the safe and stable operation of the dam. Therefore, the settlement of the upstream rockfill area of ​​earth-rock dams during the impoundment and operation periods has received increasing attention. According to the current survey of the monitoring and operation of these earth-rock dams, most of the existing dams have basically no internal deformation monitoring facilities in the upstream rockfill area during the operation period. Some existing dams have installed internal deformation monitoring facilities, generally using water-tube settlement meters, string settlement meters, beam settlement meters, and electromagnetic settlement rings. However, these monitoring methods can only monitor settlement during the construction period. After impoundment, the string settlement meters, beam settlement meters, and other electrical measuring instruments installed in the upstream rockfill area are basically ineffective. Traditional electromagnetic settlement rings require manual insertion of the measuring instrument into the borehole, making observation impossible. Water-tube settlement meters are also unable to be used due to the flooding effect of impoundment. Existing medium and high dams mainly rely on external observation piers for surface deformation monitoring. Overall, the deformation monitoring facilities in the upstream rockfill area of ​​the existing dams are basically damaged or lack the conditions for observation during the operation period. However, the settlement in the upstream rockfill area during the operation period is particularly important for analyzing whether the existing dams are operating safely and stably.

[0003] Domestic instrument manufacturers use intelligent settlement meters to monitor upstream rockfill settlement during impoundment and operation periods. However, these meters often break down before impoundment, resulting in poor performance in practical applications. Other methods involve deploying piezometers in the upstream rockfill area to indirectly measure water pressure and calculate settlement, but these methods are also limited by instrument accuracy and the complex impoundment conditions, leading to unsatisfactory results. Therefore, adopting new monitoring technologies to address the challenge of monitoring settlement within the upstream rockfill area during the operation of existing dams is both necessary and urgent. Summary of the Invention

[0004] The main objective of this invention is to provide a method for monitoring settlement in the upstream rockfill area of ​​an existing earth-core rockfill dam, thereby solving the problems mentioned in the background art.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention includes the following steps:

[0006] S1. Set up 3-4 monitoring sections in the upstream rockfill area of ​​the existing dam, and conduct vertical drilling at the normal water level and three elevations above and below the normal water level at each monitoring section.

[0007] S2. Bury a settling steel pipe in the borehole, ensuring that the top of the settling steel pipe protrudes above the normal water level, and fix a prism on the top of the settling steel pipe.

[0008] S3. Drill a hole next to the settlement steel pipe, bury the inclinometer tube in the hole, and then install the flexible inclinometer in the inclinometer tube.

[0009] S4. Fine material is used to backfill the space between the inclinometer tube and the borehole wall. A protective cover is installed on the top of the inclinometer tube to seal it. The flexible inclinometer cable passes through the protective cover and is pulled to the observation house on the top of the dam.

[0010] Preferably, in step S1, 3 to 4 vertical holes are drilled at each elevation, with the depth of each hole increasing from shallow to deep.

[0011] Preferably, in step S2, a steel plate is welded to the bottom of the settling steel pipe for sealing, and the steel plate serves as a monitoring point.

[0012] Preferably, a total station is used to measure the elevation of the prism, and the elevation of each monitoring point is calculated by the length of the settlement steel pipe, so as to observe the elevation settlement of different parts of the upstream rockfill area of ​​the dam.

[0013] Preferably, in step S3, vertical holes are drilled 1-2m away from the settlement steel pipe at each monitoring section, and the drilling depth is the same as the maximum drilling depth of the settlement steel pipe.

[0014] Preferably, in step S3, a magnetometer is set at every 3 to 4 nodes of the flexible inclinometer to correct the calculation of the horizontal displacement of the dam in the transverse and longitudinal directions.

[0015] Preferably, in step S4, the flexible inclinometer cable is pulled along the upstream dam slope through a PE pipe to the observation house on the dam crest.

[0016] This invention provides a method for monitoring settlement in the upstream rockfill area of ​​an existing earth-core, asphalt-walled rockfill dam, with the following advantages:

[0017] 1. This technical solution has a simple implementation method and effectively solves the problem of deformation monitoring in the upstream rockfill area of ​​existing dams, especially those with defects, thus improving the monitoring technology level of earth-rock dams.

[0018] 2. This technical solution not only enables settlement monitoring of the upstream rockfill area of ​​the existing dam, but also allows for automated real-time monitoring, avoiding the risks associated with manual observation.

[0019] 3. This technical solution overcomes the shortcomings of traditional technical means and innovatively proposes a new type of monitoring instrument, a flexible inclinometer, a settlement steel pipe, and a fixed prism. The flexible inclinometer is used to monitor the internal horizontal displacement distribution at different elevations in the upstream rockfill area of ​​the existing dam, and the settlement steel pipe and fixed prism are used to monitor the internal settlement of the upstream rockfill area. At the same time, it is easy to automate the implementation, making this technical solution highly feasible. Attached Figure Description

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0021] Figure 1 This is a structural view of the cross-section of the earth-rock dam monitoring section of the present invention; Detailed Implementation

[0022] Example 1

[0023] like Figure 1 As shown, the settlement monitoring method for the upstream rockfill area of ​​an existing earth-rockfill dam with asphalt core wall adopts a flexible inclinometer + settlement steel pipe + fixed prism to systematically monitor the internal deformation of the upstream rockfill area of ​​the existing dam. It is applicable to the internal deformation monitoring of the upstream rockfill area of ​​existing earth-rockfill dams with a dam height of 50m~350m.

[0024] A shape accelerometer (SAA, commonly known as a flexible inclinometer) consists of multiple continuous segments connected in series, internally composed of microelectromechanical systems (MEMS) accelerometers. Each segment has a fixed length, typically 50cm or 100cm. The flexible inclinometer is a rigid sensor array separated by flexible joints. It is a rope-like array of sensors and microprocessors, with all microprocessors sharing the same digital communication line. The basic principle of the flexible inclinometer is to calculate the bending angle θ between each segment by detecting the gravitational field of each part. Using the calculated bending angle and the known length L of each segment, the deformation Δχ of each SAA segment can be completely determined, i.e., Δχ = θ•L. Then, by arithmetically summing ∑Δχ over each segment, the deformation χ at any length from the fixed endpoint can be obtained. Flexible inclinometers possess technical advantages such as high precision, high stability, large deformation, non-uniform deformation, and high water pressure resistance, and have been widely used in deformation monitoring of slopes, tunnels, roadbeds, and bridges. Because flexible inclinometers can withstand water pressure up to 2MPa and operate normally underwater, they can be used to monitor the horizontal deformation of rockfill after water storage.

[0025] Settlement steel pipes were vertically drilled and buried in the upstream rockfill area, with the bottom of the settlement steel pipes sealed by welding with steel plates. A fixed prism was installed at the upper end of the settlement steel pipe using a threaded connection. The elevation of the steel plate at the bottom of the settlement steel pipe was calculated by measuring the actual elevation of the fixed prism using a total station, thus obtaining the settlement information at the measuring point on the steel plate.

[0026] Includes the following steps:

[0027] Step 1: Establish 3-4 monitoring sections in the upstream rockfill area of ​​the existing dam. For each monitoring section, drill vertical boreholes at three elevations above and below the normal water level (H2, H1, H3). Drill 3-4 vertical boreholes at each elevation, with the depth increasing from shallow to deep, at elevations h1, h2, h3, and h4. Drilling should only commence after the water level has dropped below the lowest borehole elevation.

[0028] Step 2: Bury settlement steel pipes into the borehole, ensuring the top of the settlement steel pipes protrudes above the normal water level, and fix a prism at the top of the settlement steel pipes; weld a steel plate to the bottom of the settlement steel pipes for sealing, and the steel plate serves as a monitoring point. Use a total station to measure the elevation of the prisms, and calculate the elevation of each monitoring point using the length of the settlement steel pipes, thereby observing the elevation settlement of different parts within the upstream rockfill area of ​​the constructed dam.

[0029] Step 3: Drill holes next to the settlement steel pipes, embed inclinometer tubes in the holes, and then install flexible inclinometers inside the inclinometer tubes. Drill vertical holes 1-2m beside the settlement steel pipes at each monitoring section, with the drilling depth matching the maximum drilling depth of the settlement steel pipes. The hole diameter is 90mm, the inclinometer tube diameter is 75mm, and the wall thickness is at least 5mm. The length of the flexible inclinometer is the same as the drilling depth. A magnetometer is installed at every 3-4 nodes of the flexible inclinometer to correct the calculated transverse and longitudinal horizontal displacements of the dam.

[0030] Step 4: Backfill the space between the inclinometer tube and the borehole wall with fine material, seal the top of the inclinometer tube with a protective cap, and pull the flexible inclinometer cable through the protective cap to the observation house on the dam crest. The fine material particle size is less than 20mm. The flexible inclinometer cable is pulled along the upstream dam slope to the observation house on the dam crest through a PE pipe.

[0031] The above embodiments are merely preferred technical solutions of the present invention and should not be considered as limitations on the present invention. The scope of protection of the present invention should be limited to the technical solutions described in the claims, including equivalent substitutions of the technical features described in the claims. That is, equivalent substitutions and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. A method for monitoring settlement in the upstream rockfill area of ​​an existing earth-core, asphalt-walled rockfill dam, characterized by: Includes the following steps: S1. Set up 3-4 monitoring sections in the upstream rockfill area of ​​the existing dam, and conduct vertical drilling at the normal water level and three elevations above and below the normal water level at each monitoring section. Drill 3 to 4 vertical holes at each elevation, with the depth of each hole increasing from shallow to deep; S2. Bury a settling steel pipe in the borehole, ensuring that the top of the settling steel pipe protrudes above the normal water level, and fix a prism on the top of the settling steel pipe. The bottom of the settling steel pipe is sealed with a steel plate, which serves as a monitoring point. The elevation of the prism was measured using a total station, and the elevation of each monitoring point was calculated by the length of the settlement steel pipe, thereby enabling the elevation settlement observation of different parts of the upstream rockfill area of ​​the dam. S3. Drill a hole next to the settlement steel pipe, bury a clinometer tube in the hole, and then install a flexible clinometer in the clinometer tube. Vertical holes are drilled 1-2m away from the settlement steel pipe at each monitoring section, with the drilling depth being the same as the maximum drilling depth of the settlement steel pipe. The flexible inclinometer is equipped with a magnetometer at every 3 to 4 nodes to correct the calculation of the dam's horizontal displacement in the transverse and longitudinal directions. S4. Fine material is used to backfill the space between the inclinometer tube and the borehole wall. A protective cover is installed on the top of the inclinometer tube to seal it. The flexible inclinometer cable passes through the protective cover and is pulled to the observation house on the top of the dam.

2. The settlement monitoring method for the upstream rockfill area of ​​an existing earth- and asphalt-core rockfill dam according to claim 1, characterized in that: In step S4, the flexible inclinometer cable is pulled through a PE pipe along the upstream dam slope to the observation house on the dam crest.

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