Friction resistance is taken into account its method of testing
Technical field
The present invention relates to a kind of friction resistance sensor, it is used for the friction resistance monitoring of open caisson and other relevant works project construction, more specifically says so and monitors dynamic and static friction resistance automatically at concrete and other works surface.Therefore the invention still further relates to the method for utilizing the dynamic and static friction resistance of this friction resistance sensor measurement.
Background technology
Hydraulic and Hydro-Power Engineering needs to adopt the method for open caisson to carry out the construction of interim retaining wall sometimes, and wherein the open caisson friction resistance is the parameter of an important design and guidance construction, and is general by the relevant CALCULATION OF PARAMETERS proposition estimated value to the borehole wall outside soil body.Because the characteristic of the different soil bodys and have related parameter to be not quite similar, the distribution situation complexity need obtain by a large amount of tests, and is time-consuming and still have than big-difference with actual conditions, and its calculated value is the maximal value under the quiescent conditions.Therefore need install in borehole wall surface and bury the friction resistance sensor underground, and adopt the robotization measuring instrument that dynamic and static friction resistance is monitored in real time.
The method of observation open caisson friction resistance generally is that the reinforcing bar meter is installed on the outer vertical structure reinforcing bar that the borehole wall is arranged on the engineering at present, by the friction resistance of answering force evaluating borehole wall outside surface of measurement structure reinforcing bar.Obviously, this method is extremely inaccurate because the actual reflection of the stress of structure reinforcing bars is that structure is born various external force and the material internal force combined stress in this position, can not accurate response should place's borehole wall outside surface friction resistance.
Summary of the invention
For accurately measuring the open caisson friction resistance, the invention provides a kind of new friction resistance meter.The present invention simultaneously also provides and has utilized this friction resistance meter to carry out the method that dynamic and static friction resistance is measured accordingly.
Friction resistance meter provided by the invention is made up of reinforcement stresses meter, friction resistance plate and pedestal backing plate; One end and the friction resistance plate of reinforcement stresses meter are fixed, and the other end is as anchored end; Friction resistance backboard face is the pedestal backing plate, at the periphery of friction resistance plate and reinforcement stresses meter and base pads sheet separation flexible material is arranged all.
Pedestal backing plate length and width size is slightly larger than the friction resistance plate, and a concave indentation is arranged at its bottom, is the installation site of reinforcement stresses meter and the fixing overlap joint of friction resistance plate.
The anchored end of reinforcement stresses meter is one section elbow bar of spreading in addition, strengthens anchorage effect.
At different needs, described reinforcement stresses meter can be dissimilar reinforcing bar meter or dynamometer.
Friction resistance meter provided by the invention can be applied to the friction resistance of various concrete or other structural plane and measure.
The present invention also provides the method for using friction resistance meter provided by the invention that the open caisson friction resistance is measured.
1) friction resistance meter provided by the invention vertically is installed in the outside surface of caisson wall, friction resistance plate 2 outside surfaces are flushed with borehole wall outside surface;
2) adopt measurement instrument to detect the stress that the reinforcement stresses meter is born, thereby try to achieve the friction resistance f ' that friction resistance plate 3 is born;
3) extrapolate the friction resistance F '=f '/s of unit area according to the area s of friction resistance plate;
4) according to distribution and the measured value of friction resistance meter at the open caisson periphery, adopt method of interpolation to calculate open caisson periphery unit area friction resistance size and distribution, determine the friction resistance of open caisson.
In the prior art, provide robotization detecting unit equipment.
The variation of borehole wall friction resistance mainly shows as: when static at the bottom of (when open caisson stops sinking construction) open caisson the mouth counter-force bigger, borehole wall friction resistance is less, the mouth counter-force equals open caisson with closing of borehole wall friction resistance and conducts oneself with dignity at the bottom of this moment open caisson.In well sinking when construction,, the mouth counter-force reduces rapidly at the bottom of the open caisson, and borehole wall friction resistance increases to maximum value gradually, and when closing of mouth counter-force at the bottom of the open caisson and borehole wall friction resistance conducted oneself with dignity less than open caisson, open caisson began sinking.When if borehole wall friction resistance is conducted oneself with dignity greater than open caisson, even the mouth counter-force is zero at the bottom of the open caisson, open caisson can not sink voluntarily, must overcome the influence of friction resistance in the pressurization of open caisson top.
The friction resistance monitoring is carried out in above-mentioned well sinking work progress in real time, needs the robotization follow-on test.When the sinking construction of open caisson, open caisson wall friction resistance is carried out dynamic and static monitoring, provide reliable field data, for controlling and instructing the sinking construction of open caisson that necessary measured data is provided for open caisson designs with the drop shaft sinking Construction Study.
Friction resistance meter provided by the invention directly contacts with measured surface, can react the friction resistance of testee more accurately.
Description of drawings
Fig. 1 is a friction resistance meter structural drawing;
Fig. 2 be among Fig. 1 A-A to sectional view.
1---reinforcement stresses meter 2---friction resistance plate 3---pedestal backing plate 4---reinforcing bar anchorage head 5---flexible filler wherein
Embodiment
Friction resistance meter provided by the invention is made up of three critical pieces, i.e. reinforcement stresses meter 1, friction resistance plate 2 and pedestal backing plate 3, and friction resistance plate and pedestal backing plate are steel plate.One end of reinforcement stresses meter 1 and 2 welding of friction resistance plate are fixing, and elbow reinforcing bar 4 of other end lengthening welding is as anchored end.Friction resistance plate 1 back side is pedestal backing plate 3, and the length and width size is slightly larger than friction resistance plate 2, and its surface of contact is smooth plane, and brushes a little grease power of reducing friction.Friction resistance plate 2 outside surfaces are coarse hair side, and its roughness coefficient need be simulated the concrete roughness coefficient of the borehole wall, make that the unit frictional resistance power of unit frictional resistance power that friction resistance plate 2 produces and borehole wall concrete surface is basic identical.The size of friction resistance plate 2 determines that according to the sensitivity of the reinforcement stresses meter that is adopted the measured value of the big more friction resistance meter of size is big more, and is also low more to the requirement of reinforcement stresses meter sensitivity.When building the open caisson concrete, with the vertical surface that is embedded in the borehole wall of installing of friction resistance meter, friction resistance plate 2 is towards the outside, and its peripheral filling flexible filler 5 in company with well sinking, bears the friction resistance in the borehole wall outside after treating concrete setting and reaching design strength.
In fact the well sinking construction is a dynamic process, by to be arranged in each sensor in the caisson structure (comprise be arranged in around the outside the friction resistance meter) real-time monitoring, can understand and control the sinking construction of open caisson, also provide the reliable technique data simultaneously for open caisson design.
The friction resistance meter that the present invention proposes is used in the open caisson construction of Xiang Jiaba power station first, comprise the friction resistance meter manufacturing, bury underground, the foundation of automatic monitoring system and set up computation model and work such as data analysis, obtained achievement data.Above embodiment friction resistance monitoring specific practice and unit frictional resistance power are calculated and are described below:
1) the reinforcement stresses meter adopts highly sensitive string formula reinforcing bar meter (specification Φ 18mm), friction resistance board size 600x500mm
2, area S=0.3m
2, thickness δ=20mm, quality m=46.8kg.
2) open caisson height 49m is divided into the construction of building the well body concrete (at every turn building the 7m height) and the 7m that once sinks for 7 times, finally makes the high well body top of 49m concordant with ground.
3) horizontal section of 4 differing heights of friction resistance score is arranged in borehole wall outer surface, and according to the well body concrete segmentation is built progressively and is buried underground, Cables for Dam Observation all causes the research station that is positioned at ground, adopts the robotization detecting unit to monitor under the control of computing machine.
4) in the front and back and process of well sinking, the friction resistance meter of having imbedded is tested, promptly read the stress value σ of reinforcing bar meter
g, suffered load P=σ
g* A
g, then act on the friction resistance value f '=P+mg on the friction resistance plate.
5) in a certain moment of well sinking construction, the actual measurement reading that is arranged in a certain the friction resistance meter in the borehole wall outside is σ
g=4.6MPa, then the unit frictional resistance power F ' of this friction resistance meter position is calculated as follows:
F′=f′/s
=(P+mg)/s
=(σ
g*A
g+mg)/s
=(4.6*10
6*3.14*0.009
2+46.8*9.8)/0.3
=(1169.964+458.64)/0.3
=5428.68Pa。