| NEWS MODEL EXPERIMENT
The model includes three parts: the main model, the system of water supply and
drainage, and monitoring system (Figure3-1).
1. The main model
The main model is 3.0 meters in height, and 2.0 meters in both width and length. It can
be separated to two parts. The upper is a soil box which is used to contain soil to
simulate the natural overburden, it is 1.5 meters in height. The lower consists of pipes
used to model caves and openings in underlying limestone. The pipe is connected with the
soil box by interface.(see figure3-2)
2. The system of water supply and drainage
Two separated systems of water supply and drainage are provided for both soil box and
pipes so as to alter the hydrodynamic condition, which have an effect on sinkhole
development.
(1) The water supply and drainage system for soil include:
water box: installed at two sides of soil box in which the constant water head can hold
the water table in soil.
sprinklers: fixed on the top of soil box to model the raining, precipitation can be
measured by water meter.
drainage: the pore water in soil could be drained to the pipes through the opening in
the bottom of soil box.
(2) The water supply and drainage system for karst cave
The supply water box is 3.5 meters in height. The water pressure in it may increase to
0.1 MPa, in order to model the hydrodynamic condition of confined karst water. The karst
water level will decline by pumping.
3. The monitoring system
(1) Monitoring karst water regime
A valve is use to control water flow, a water meter and pressure gauge to measure karst
water flow velocity and water level, respec-tively.
(2) Monitoring pore water regime (see figure3-A)
Piezometer tubes fixed at the bottom of the soil box is used in measuring pore water
level.
(3) Measuring soil deformation
It is performed by a subsidence tube as shown on Figure3-B.
A clock gauge and a small piece of iron-sheet are connected by a silk thread within a red
copper tube. The deformation of soil causes the iron sheet to move and, in turn, is
reflected at the gauge. The gauge readings indicate the vertical deformation.
The similarity of physical model and geological model
In the model experiment, all of the geological structure, properties of overburden, the
hydrodynamic condition and the rainfall are similar to what in nature.
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