Cutting creep instrument
Technical field
The present invention relates to be used in the Geotechnical Engineering field measure the device of native creep properties, particularly a kind of cutting creep instrument.
Background technology
Under ideal state, soil body test specimen is to be normal stress F at vertical acting force
vWith horizontal applied force be shear stress F
hActing in conjunction destroy down F wherein
vMust be vertical acting force, the desirable failure mode of test specimen should be the parallel changing of the relative positions of a side with respect to opposite side.The flow graph of present domestic use generally adopts long lever mechanism to apply vertical and horizontal loading, yet adopt the leverage load application to have the defective of following several respects: the shear box size of (1) domestic boxshear apparatus that generally adopts is less than normal, and area is generally 30cm
2, first when soil sample is sheared from the sample edge, and circular box has formed the obvious stress concentration phenomenon in edge at the very start, in whole shear history, there is the uneven problem of shearing stress distribution in the application point place shear stress maximum near shear box all the time; (2) soil sample distortion in a single day, lever can tilt, and the direction of vertical force can tilt change applied force F in the experiment because of lever
vIncreasing, the angle of lever and horizontal direction is also increasing, F
vBe not all the time perpendicular to shear surface, but one angle arranged,, thereby caused loading error increasing yet along with the raising that experimental precision is required with vertical direction, cause test figure than large deviation, experiment showed, F
vThe angle of internal friction of gained and cohesive strength are all greater than F during out of plumb
vValue when vertical; (3) two-wayly all adopt the lever reinforcing, make equipment volume huge, because the length of lever can not be oversize, loaded value is limited, and capacity value does not reach the sample actual loading.Maximum horizontal shear stress is 300kPa, and vertical normal stress is 400kPa.If consider above-mentioned first defective, increase the sample area, as increase to 10 * 10=100cm
2If, adopting traditional lever force mechanism, the maximum horizontal stress that provides is respectively 90kPa and 120kPa with vertical normal stress, is equivalent to the suffered natural stress of 6 meters soil samples of degree of depth less than.
Summary of the invention
The objective of the invention is the deficiency that exists at prior art, a kind of simple in structure, stable work in work, accuracy height are provided, use easy to operate cutting creep instrument.
Technical scheme of the present invention is: a kind of cutting creep instrument, comprise testing table 1, be positioned at testing table 1 and be provided with the shear box of forming by down cut box 2 and last shear box 3, the top of described shear box is provided with pressure cap 4, pressure cap 4 is provided with pressure transducer 5, one side of last shear box 3 is connected with pulling force sensor 10, it is characterized in that: described pressure transducer 5 loads pulley blocks 8 by power transmission framework 6 and pressure at right angle and is connected; Down cut box 2 loads pulley blocks 7 by traction rope and horizontal shear and is connected; Being arranged on pressure at right angle loading pulley blocks 8 is connected with counterweight 9 with the movable end that horizontal shear loads the traction rope on the pulley blocks 7.
The present invention compared with prior art has the following advantages:
(1) the present invention replaces the leverage of traditional instrument with pulley blocks, and in order to enlarging pressure at right angle and the horizontal shear that is applied to soil sample by counterweight, so it is simple for structure, and volume is little, working stability, test accuracy height.
(2) dirigibility of pulley blocks mechanism is good, if when needed horizontal or vertical load is very big, can two pulley blocks and usefulness, also can change the pulley blocks of wide range, thereby satisfy the needs of actual engineering.
Description of drawings
Fig. 1 is a structural representation of the present invention.
Embodiment
The invention will be further described below in conjunction with accompanying drawing.
As shown in Figure 1, the present invention includes testing table 1, be positioned at testing table 1 and be provided with the shear box of being made up of down cut box 2 and last shear box 3, the top of described shear box is provided with pressure cap 4, pressure cap 4 is provided with pressure transducer 5, and a side of last shear box 3 is connected with pulling force sensor 10; Described pressure transducer 5 loads pulley blocks 8 by power transmission framework 6 and pressure at right angle and is connected; Down cut box 2 loads pulley blocks 7 by traction rope and horizontal shear and is connected; Being arranged on pressure at right angle loading pulley blocks 8 is connected with counterweight 9 with the movable end that horizontal shear loads the traction rope on the pulley blocks 7.
Described shear box is square.
Described pressure at right angle loads the below that pulley blocks 8 and horizontal shear loading pulley blocks 7 and counterweight 9 all are arranged on testing table 1.
Pressure at right angle of the present invention loads and pulley blocks mechanism is all adopted in the horizontal shear loading.Pulley blocks be by fixed pulley and running block altogether can the laborsaving device that can change the direction of power again.In actual engineering, the thickness of general major landslip can reach 30m, and the native maximum horizontal shear stress that is subjected to of estimation is that 300kPa, maximum perpendicular compressive stress are 600kPa thus.In experiment, if the soil sample area is big, is unpractical to the power that soil sample applies above-mentioned size directly, and it is also limited to adopt lever to add the range of vertical force with counterweight, along with the distortion of soil also can produce a series of errors, if adopt pulley blocks mechanism then to have good dirigibility.If when pressure at right angle of the present invention adds pulley blocks five travelling block of 8 employings and four fixed pulleys compositions, then pressure at right angle can be enlarged 10 times (disregarding friction), if will apply the vertical compressive stress of 600kPa, when area is 100cm to soil sample
2The time, required load is 6kN, and 9 need of counterweight can meet the demands when being added to 0.6kN; Horizontal shear loads pulley blocks 7 and adopts two travelling block and two fixed pulleys to form, and horizontal shearing stress can be enlarged 5 times, if will apply the horizontal shearing stress of 300kPa to soil sample, when required load was 3kN, counterweight only need be added to 0.6kN and get final product.Therefore, level and vertical load reach maximal value, and the counterweight that only adds 60kg is to be feasible fully.