Facilities

National Central University Geotechnical Centrifuge

The NCU geotechnical centrifuge was manufactured by ACTIDYN and inaugurated in 1995. With arm radius of 3 m and the swing basket dimension of 80 cm × 100 cm × 80 cm (L×W×H). Under static test conditions, the centrifuge can be accelerated up to 200 g with maximum payload of 550 kg and capacity of 100 g-ton.

ES-18A single-axis geotechnical centrifuge shaker

ES-18A single-axis geotechnical centrifuge shaker was designed by PVL Technologies, Inc. and installed on NCU geotechnical centrifuge swing basket in 2008. It is a servo-hydraulic controlled shaker designed to produce 1-D translational shaking in response to an applied input voltage signal. The shaker provides a maximum nominal shaking force of 53.4 kN with a maximum table displacement of ± 6.4 mm and accelerations up to 80 g with a maximum payload of 400 kg. The nominal operating shaking frequency range is 0-250 Hz and the payload dimensions is 1.0 m × 0.55 m (L×W).

Equipment apparatus

In NCU-GCST Laboratory, the traveling pluviation system is used to prepare the sandy soil model. This system changes the relative density of soil by changing its drop height. In addition, we have consolidation system to prepare the soil deposit made out of clay material. The wet tampping method can be used to prepare the density of soil. The Saturation system is essential to investigate the model in a saturated condition, such as liquefaction and seismic behavior. This system includes a vacuum pump, a water reservoir, and a saturation box.

The surface scanner system consists of three parts, which are the motor, aluminum alloy frame, and laser displacement transducers. This system can be placed on the centrifuge basket before and after the centrifuge modeling test to investigate the change of soil strata. In addition, it can be placed on top of the fault simulation container to observe the evolution of surface deformation during the centrifuge flight.

The rainfall system provides water to simulate rainfall by several nozzles and is assembled under the lid of the container. The rainfall intensity can be controlled by the number of nozzles or air pressure from the water tank. The plastic tube connects several nozzles to a water tank, and we can provide the air pressure into the water tank in the control room. After that, open the water valve to let the water flow into the centrifuge chamber during the centrifuge flight.

Regarding the photo and video devices, we have two types of wi-fi cameras: SJCAM 5000X and GoPro Hero9. Moreover, a webcam can be set up on the side of the centrifuge basket to monitor the model during the test. The spaghetti penetration system is used to penetrate the spaghetti into the saturated model. Therefore, the spaghetti absorbs the viscous fluid and deforms with the soil strata. After the test, we can suck out the fluid and cut the soil profile to observe the deformation of the soil.

The cone penetration test (CPT) system consists of laser displacement transducer, ball screw, load frame, cone-rod, and cone. The motor can provide constant speed while the cone penetrates the soil during the centrifuge modeling test, and the CPT tip resistance distribution along the depth can be drawn.

Types of Soil Containers

In NCU-GCST Laboratory, six types of soil containers are designed to simulate and study geotechnical engineering problems. Two containers with fixed boundary conditions can contain dry and saturated soil models named 2D rigid box and 3D rigid box under static or dynamic test. With the inner dimension of 736 mm × 200 mm × 350 mm and 767 mm × 355 mm × 400 mm (Length × Width × Height), respectively.

A laminar container consists of 38 lightweight aluminum alloy rings arranged in a stack. Each ring is 8.9 mm in height and separated from adjacent rings by roller bearings, which are designed to permit translation in the longitudinal direction with a minimal friction coefficient of 0.01. The laminar container is designed to contain dry and saturated soil models and permit the development of stresses and strains that approach 1-D shear wave propagation conditions.

The fault simulation box is a special container that can simulate both normal and reverse fault slip conditions. The fault dip angle simulation is 60 degrees with the maximum throw of 55 mm, and the maximum vertical movement rate of 2.5 mm/minute. The circular container is consists of four hollow semi-cylinder to study the the effect of earthquake-induced vibration on the canister, buffer and disposal hole.

In addition, a wave simulation container consists of waterproof air cylinder, wave panel, and aluminum alloy frame with the dimension of 1200 mm × 300 mm × 500 mm (Length × Width × Height). Aluminum alloy is utilized to make a container with one side of acrylic to obtain the action of waves. The wave can be generated through the air cylinder pushing and pulling controlled by remoted computer in centrifuge control room.

Data acquisition system and sensors

The data acquisition system is essential equipment to record the sensor data. The National Instrument DAQ system is used to obtain a high sampling rate of sensor measurement in the NCU-GCST Laboratory. Different types of sensors are used to measure one of the physical properties for centrifuge modeling tests. Depending on the specific requirement for the tests, several sensors can be placed in the model, such as accelerometer, Fiber Bragg Gratting pore pressure transducer, electronic pore pressure transducer, earth pressure sensor, linear variable displacement transformer, load cell, laser displacement transducer, and Strain gauge (Full Wheatstone Bridge).