CN111141675A - Monitoring method for prejudging dam gallery concrete cracking - Google Patents
Monitoring method for prejudging dam gallery concrete cracking Download PDFInfo
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- CN111141675A CN111141675A CN202010030064.1A CN202010030064A CN111141675A CN 111141675 A CN111141675 A CN 111141675A CN 202010030064 A CN202010030064 A CN 202010030064A CN 111141675 A CN111141675 A CN 111141675A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N19/00—Investigating materials by mechanical methods
- G01N19/08—Detecting presence of flaws or irregularities
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
- G01B7/16—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring the deformation in a solid, e.g. by resistance strain gauge
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Abstract
The invention belongs to the technical field of water conservancy and hydropower, and particularly relates to a monitoring method for prejudging dam gallery concrete cracking. According to the dam gallery, the reinforcing steel bars and the unidirectional strain gauges are respectively arranged on the crown arch and the arch shoulder of the dam gallery, so that the change conditions of concrete strain and reinforcing steel bar stress can be found in time before a concrete crack is observed by naked eyes, the change conditions of the crack can be found in time at the early stage of the crack or the crack generation, the relevant influence factors generated by the crack can be analyzed in time, and corresponding treatment measures are taken to prevent the crack from generating or pre-control the crack to the minimum scale. The monitoring method provided by the invention has very positive guiding significance for the construction of subsequent engineering.
Description
Technical Field
The invention belongs to the technical field of water conservancy and hydropower, and particularly relates to a monitoring method for prejudging dam gallery concrete cracking.
Background
In the hydraulic and hydroelectric engineering, the dam concrete gallery has a phenomenon that cracks are easy to occur in the gallery (particularly a crown arch) due to various factors such as complex structural stress (a gallery stress finite element calculation result is shown in figure 1) and difficulty in controlling the concrete construction quality, and particularly in a high concrete dam, the dam gallery cracks are shown in figure 2. The appearance is influenced if the gallery cracks are generated, and the stress of the dam structure is influenced if the gallery cracks are generated, so that the engineering safety is endangered. Therefore, dam gallery cracks have been a difficult problem for water conservancy and hydropower design engineers.
Aiming at the problem of concrete cracking of a dam gallery, the traditional monitoring mode is found by manual inspection in a construction period, and due to the fact that a gallery crown is generally high, construction interference such as gallery maintenance is large, the identification degree of naked eyes is low, and the timeliness of finding cracks is poor; after the crack is generated, the development condition of the opening degree of the crack is usually qualitative judgment or realized by adopting a simple monitoring means, and the crack opening degree monitoring method is low in precision and poor in regularity. The specific time of crack generation is often difficult to determine, which brings difficulty to the analysis of the reason of follow-up crack generation, and the traditional monitoring mode of gallery crown crack has poor timeliness, low precision and poor achievement rule.
Disclosure of Invention
The invention aims to provide a monitoring method for prejudging dam gallery concrete cracking.
For this reason, the above object of the present invention is achieved by the following technical solutions:
a monitoring method for prejudging dam gallery concrete cracking is characterized by comprising the following steps: the monitoring method for prejudging dam gallery concrete cracking comprises the following steps:
(1) 1 reinforcing steel bar meter and 1 unidirectional strain meter are respectively arranged on a positive arch and a left arch shoulder and a right arch shoulder of a dam gallery, the reinforcing steel bar meters are welded on inner circumferential reinforcing steel bars, and the unidirectional strain meters are embedded in concrete near the inner reinforcing steel bars welded by the reinforcing steel bar meters;
(2) cables of the reinforcing steel bar meter and the unidirectional strain gauge are led to a threading pipe on the side wall of the dam gallery along the reinforcing steel bars and led to a monitoring instrument;
(3) when concrete is poured on the upper part of the dam gallery, timely observing the reinforcing steel bar meter and the unidirectional strain gauge, and observing the concrete once every 4 hours at the initial stage of concrete pouring until the hydration reaction of the concrete reaches the highest temperature; observing once a day later for one ten days; observing for three times every ten days, and continuously observing for 1 month; observations were made weekly thereafter;
(4) after measuring by a monitoring instrument each time, converting the original quantity into a required monitoring physical quantity, drawing a process curve, and judging whether an observed value is abnormal or not;
(5) through analyzing data and a process curve, when the measurement values of the reinforcing steel bar meter and the strain gauge are suddenly changed, namely the measurement values of two adjacent measurement values of the reinforcing steel bar meter are more than 10 MPa, the measurement values of two adjacent measurement values of the strain gauge are more than 50 micro-strain, or the observation values are obviously increased after several continuous periods, the dam corridor is judged to possibly generate cracks.
While adopting the technical scheme, the invention can also adopt or combine the following technical scheme:
as a preferred technical scheme of the invention: the height of the inner layer steel bar of the welded steel bar meter is properly increased so as to ensure the thickness of the protective layer of the concrete under the condition that the height in the dam gallery meets the design requirement.
As a preferred technical scheme of the invention: when the reinforcing bar meter is welded, the two ends of the reinforcing bar meter are wrapped by the moist geotextile.
As a preferred technical scheme of the invention: the distance between the one-way strain gauge and the left and right annular reinforcing steel bars parallel to the one-way strain gauge is 10 cm.
As a preferred technical scheme of the invention: the arch shoulder of the steel bar meter is arranged at a position of 30-45 degrees.
The invention provides a monitoring method for prejudging dam gallery concrete cracking, which has the following beneficial effects: by arranging the reinforcing steel meters and the unidirectional strain gauges on the top arch and the arch shoulder of the dam gallery respectively, the change conditions of concrete strain and reinforcing steel stress can be found in time before concrete cracks are observed by naked eyes, the change conditions of the cracks can be found in time at the early stage of the cracks or the cracks can be generated, related influence factors generated by the cracks can be analyzed in time, and corresponding treatment measures are taken to prevent the cracks from being generated or pre-control the cracks to the minimum scale. The monitoring method provided by the invention has very positive guiding significance for the construction of subsequent engineering.
Drawings
FIG. 1 is a cloud diagram of finite element calculation results of stress of a dam corridor.
Fig. 2 is a top arch crack diagram of a high arch dam gallery.
Fig. 3 is a cross-sectional view of a dam corridor provided with a rebar meter and a strain gauge according to the present invention.
Fig. 4 is a layout view in the direction a in fig. 3.
Fig. 5 is a layout view in the direction B in fig. 3.
Detailed Description
The invention is described in further detail with reference to the figures and specific embodiments.
1. As shown in fig. 3 and 4, 1 steel bar meter and one-way strain meters are respectively arranged on a front arch and a left and right 30-degree arch shoulders of a gallery, the steel bar meters are welded on first-layer circumferential steel bars, and the one-way strain meters are embedded between the two first-layer circumferential steel bars, are arranged in parallel to the circumferential steel bars and are 10 cm away from the steel bars on two sides.
2. As shown in fig. 5, the thickness of the concrete protective layer is affected after the steel bar meter is installed, so the circumferential steel bar of the steel bar meter is properly increased, and the protective layer thickness required by the design is still ensured.
3. And (3) wrapping the two ends of the reinforcing bar meter by using the moist geotextile for reducing the influence of the temperature on the measured value of the reinforcing bar during the welding of the reinforcing bar meter.
4. The cable of the monitoring instrument is pulled out from the threading pipe on the side wall of the corridor along the steel bar.
5. Observing the reinforcing steel bar meter and the unidirectional strain gauge in time when concrete is poured on the upper part of the corridor, and observing the reinforcing steel bar meter and the unidirectional strain gauge for 1 time every 4 hours at the initial stage of concrete pouring until the hydration reaction of the concrete reaches the highest temperature; observing for 1 time every day for one ten days; observing for 3 times in each ten days later and continuously observing for 1 month; observations were made 1 time per week thereafter.
6. After each measurement and reading of the instrument, the original quantity is converted into the required monitoring physical quantity, a process line is drawn, and whether the measured value is abnormal or not is judged.
7. By analyzing data and process lines, when the tensile stress and strain of the steel bar are suddenly changed, namely the stress measurement difference of two adjacent steel bars is more than 10 MPa, the stress measurement difference of two adjacent strain measurements is more than 50 micro-strain, or the observed values are continuously and obviously increased for several periods, the problems of observation errors, calculation and the like are firstly eliminated, the defects are not found, the possibility of generating cracks is pre-judged, and corresponding measures are taken in time.
8. When the pre-judging corridor is likely to generate cracks, the observation frequency is increased to more than 6 times/day (including instrument monitoring and manual corridor inspection appearance), and intervention is carried out through engineering measures, including: the method has the advantages of strengthening gallery heat preservation maintenance, delaying the pouring time of dam body concrete at the upper part of the gallery, delaying the form removal time of galleries at adjacent parts, increasing steel supports in the gallery and the like, so as to achieve the purpose of pre-controlling the generation of cracks or reducing the scale of the cracks.
The above-described embodiments are intended to illustrate the present invention, but not to limit the present invention, and any modifications, equivalents, improvements, etc. made within the spirit of the present invention and the scope of the claims fall within the scope of the present invention.
Claims (5)
1. A monitoring method for prejudging dam gallery concrete cracking is characterized by comprising the following steps: the monitoring method for prejudging dam gallery concrete cracking comprises the following steps:
(1) 1 reinforcing steel bar meter and 1 unidirectional strain meter are respectively arranged on a positive arch and a left arch shoulder and a right arch shoulder of a dam gallery, the reinforcing steel bar meters are welded on inner circumferential reinforcing steel bars, and the unidirectional strain meters are embedded in concrete near the inner reinforcing steel bars welded by the reinforcing steel bar meters;
(2) cables of the reinforcing steel bar meter and the unidirectional strain gauge are led to a threading pipe on the side wall of the dam gallery along the reinforcing steel bars and led to a monitoring instrument;
(3) when concrete is poured on the upper part of the dam gallery, timely observing the reinforcing steel bar meter and the unidirectional strain gauge, and observing the concrete once every 4 hours at the initial stage of concrete pouring until the hydration reaction of the concrete reaches the highest temperature; observing once a day later for one ten days; observing for three times every ten days, and continuously observing for 1 month; observations were made weekly thereafter;
(4) after measuring by a monitoring instrument each time, converting the original quantity into a required monitoring physical quantity, drawing a process curve, and judging whether an observed value is abnormal or not;
(5) through analyzing data and a process curve, when the measurement values of the reinforcing steel bar meter and the strain gauge are suddenly changed, namely the measurement values of two adjacent measurement values of the reinforcing steel bar meter are more than 10 MPa, the measurement values of two adjacent measurement values of the strain gauge are more than 50 micro-strain, or the observation values are obviously increased after several continuous periods, the dam corridor is judged to possibly generate cracks.
2. The method for monitoring the prejudgment of the dam corridor concrete cracking according to claim 1, wherein the method comprises the following steps: the height of the inner layer steel bar of the welded steel bar meter is properly increased so as to ensure the thickness of the protective layer of the concrete under the condition that the height in the dam gallery meets the design requirement.
3. The method for monitoring the prejudgment of the dam corridor concrete cracking according to claim 1, wherein the method comprises the following steps: when the reinforcing bar meter is welded, the two ends of the reinforcing bar meter are wrapped by the moist geotextile.
4. The method for monitoring the prejudgment of the dam corridor concrete cracking according to claim 1, wherein the method comprises the following steps: the distance between the one-way strain gauge and the left and right annular reinforcing steel bars parallel to the one-way strain gauge is 10 cm.
5. The method for monitoring the prejudgment of the dam corridor concrete cracking according to claim 1, wherein the method comprises the following steps: the arch shoulder of the steel bar meter is arranged at a position of 30-45 degrees.
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| CN202010030064.1A CN111141675A (en) | 2020-01-13 | 2020-01-13 | Monitoring method for prejudging dam gallery concrete cracking |
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Application publication date: 20200512 |