Test apparatus for early landslide detection fully-connected with pore water pressure, surface displacement and shear surface
Disclosed herein is a test apparatus for early landslide detection fully-connected with pore water pressure, surface displacement and shear surface. The test apparatus calculates a factor of safety of a slope based on variation in pore water pressure, surface displacement and shear surface of a soil mass, and predicts a change in factor of safety, thus making early landslide detection possible. In the test apparatus, while a container of a slider is moved with a soil mass loaded into the container, shear surface and surface displacement environment is provided, and the shear strength and the shear stress of the soil mass can be calculated based on the pore water pressure and the weight of the soil mass. Thereby, the factor of safety of the soil mass can be calculated, and early landslide detection can be realized by using variation of the factor of safety of the slope.
1. A test apparatus for early landslide detection fully-connected with pore water pressure, surface displacement and shear surface, the test apparatus comprising:
a frame;
a flume installed on the frame so as to be adjustable in angle, the flume providing a slope for landslide materials;
a slider coupled to the flume so as to be movable in a longitudinal direction of the flume, with a soil mass loaded into the slider, the soil mass constituting the landslide materials, the slider providing a shear surface of the soil mass, wherein the slider moves along with the soil mass in the longitudinal direction of the flume and simulates a surface displacement of an upper part of the soil mass and a slope failure of a lower surface of the soil mass; and
a calculation unit calculating shear strength and shear stress on a failure plane of the slope based on pore water pressure and weight of the soil mass depending on the movement of the slider, and calculating a factor of safety of the slope based on the calculated shear strength and shear stress.
2. The test apparatus as set forth in claim 1 , wherein the calculation unit comprises:
a weight sensor installed in a bottom plate of the slider, the weight sensor measuring the weight of the soil mass depending on the movement of the slider;
a pore water pressure sensor installed in an inner surface of the slider, the pore water pressure sensor measuring the pore water pressure in the soil mass; and
a calculation server calculating the shear strength and shear stress of the slope based on measured values transmitted from the weight sensor and the pore water pressure sensor and then calculating the factor of safety of the slope based on the calculated shear strength and shear stress.
3. The test apparatus as set forth in claim 2 , wherein the calculation server uses:
a following [formula 1] to calculate the shear strength on the failure plane of the slope;
a following [formula 2] to calculate the shear stress on the failure plane of the slope; and
a following [formula 3] to calculate the factor of safety of the slope
shear strength=cohesion+effective stress×tan (internal friction angle)
effective stress=total stress−pore water pressure of pore water pressure sensor [formula 1]
(the cohesion, the internal friction angle and the total stress are preset constants)
shear stress=the sum of forces causing activities obtained by the weight measured by the weight sensor [formula 2]
factor of safety=shear strength/shear stress. [formula 3]
4. The test apparatus as set forth in claim 2 , wherein the calculation unit further comprises:
a sensor holder formed in the inner surface of the slider, the sensor holder having a depression shape, with the pore water pressure sensor embedded in the sensor holder; and
a sensor filter provided in an upper end of the sensor holder, the sensor filter allowing water to enter the sensor holder and filtering out foreign materials other than water.
5. The test apparatus as set forth in claim 1 , wherein the slider comprises:
a container movably provided on the flume, the container having a box shape open on an upper end thereof, with the soil mass loaded in the container so that the container simulates the shear surface on the lower surface of the soil mass;
a cover covering the open upper end of the container; and
an actuator movably supporting the container and controlling movement of the container or a speed of the movement thereof.
6. The test apparatus as set forth in claim 5 , wherein the actuator comprises
a hydraulic cylinder connected to an end of the container to support the container, the hydraulic cylinder contracting or extending a length thereof and thus moving the container.
7. The test apparatus as set forth in claim 5 , wherein the slider further comprises
a collapsed-slope simulation unit providing a rough surface to a bottom surface of the container and thus simulating a rough surface of a collapsed slope on the lower surface of the soil mass.
8. The test apparatus as set forth in claim 7 , wherein the collapsed-slope simulation unit comprises:
a winding roller provided on a first side plate of the container;
a rough surface member wound around the winding roller and interposed between the bottom surface of the container and the lower surface of the soil mass while a front end of the rough surface member is pulled towards a second side plate of the container, the rough surface member being made of a material having a predetermined surface roughness to provide a rough surface;
a pulling-out roller provided at a position spaced apart from the container, the pulling-out roller winding the front end of the rough surface member therearound and pulling the rough surface member from the winding roller; and
a slot formed in the second side plate of the container so that the rough surface member is linearly connected to the pulling-out roller through the slot.
9. The test apparatus as set forth in claim 8 , wherein the rough surface member is made of any one of a non-woven fabric having a predetermined surface roughness, a sand paper and a member having protrusions on a surface thereof to provide a predetermined surface roughness.
10. The test apparatus as set forth in claim 8 , wherein the collapsed-slope simulation unit further comprises
a water sealing member provided in the slot, the water sealing member coming into close contact with the rough surface member and prevent water contained in the soil mass from leaking out of the container through the slot.
11. The test apparatus as set forth in claim 5 , wherein the slider further comprises
a plurality of flume rollers rotatably provided on and arranged along a bottom surface of the flume, the flume rollers providing a slip plane for the container.
12. The test apparatus as set forth in claim 5 , wherein the slider further comprises
a rain simulation unit installed in the cover, the rain simulation unit supplying water onto an upper portion of the soil mass and providing a simulated rain environment to the soil mass.
13. The test apparatus as set forth in claim 12 , wherein the rain simulation unit comprises:
a plurality of spray nozzles installed in and arranged along a lower surface of the cover, the spray nozzles spraying water towards the soil mass; and
a supply pump supplying water to the spray nozzle.
14. The test apparatus as set forth in claim 1 , further comprising
a camera provided above the flume, the camera photographing movement of the slider to determine a position of the slider or conditions of the soil mass loaded in the slider depending on the movement of the slider.