Sharif University of Technology

Sharif University of Technology

Civil Engineering Department

Laboratory Investigations on

Underwater Landslide Generated Waves

Landslides, which often accompany large earthquakes, can disturb the overlying water column as sediment and rock slump down slope. Any sort of geophysical mass flow, including debris flows, debris avalanches, landslides, and rock falls can generate impulsive waves.

Landslide generated waves can have a disastrous potential of damage combined with a significant degree of uncertainty. Generation and propagation of impulse waves have complex mechanism that may be divided into four parts: slide motion, initial water surface fluctuation induced by energy transfer from landslide to water, impulse wave propagation in the water body and wave run-up along the shores.

The laboratory experiments can be considered as the most reliable and possible methods to investigate the impulse wave characteristics caused by landslides. Literature review (following Table) shows that the conducted laboratory works can be classified in four categories based on the method that landslides were modeled including; sub-aerial landslides considered as rigid sliding block, sub-aerial slide modeled as deformable sliding mass, underwater landslide modeled as solid block, and deformable submarine failure mass.

Ref.	Tank Dim.					Bed slope (degree)	Failure Mass Specifications		Model Dim.	Wave Stage
	L(m)	W(m)			H(m)
Category 1:
Johnson and Bermel, 1949	Shallow Water Tank					-	Steel Plate		-	G
Wiegel, 1955	Shallow Water Tank					-	Steel Plate		-	G
Prins, 1958	Shallow Water Tank					-	Steel Plate		-	G
Kamphuis and Bowering, 1972	Shallow Water Tank					45	Steel Box		-	G
Heinrich, 1992	4.0		0.3	2.0		45, 30	Triangle Solid Block (50x50cm)		2VD	G
Walder et al., 2003	3.0		0.285	1.0		10~20	Hollow Rectangular Nylon Box		2VD	G
Panizzo et al., 2005	11.5		6	0.8		16~36	Solid Rectangular Box		3D	G, P, R
Category 2:
Fritz et al., 2004	11		0.5	1.0		45	Failure Soil Mass Caused by PLG		2VD	G, P
Category 3:
Watts, 1998	9.14		0.101	0.66		45	PVC Triangle-section (86 x 86 mm)		2VD	G
Grilli and Watts, 2005	30		3.6	1.8		15	Semi-Ellipse Aluminum Sheet		2VD	G, P
Enet et al., 2003	30		3.6	1.8		15	Semi-Ellipse Aluminum Sheet		3D	G, P
Category 4:
Heinrich, 1992	4.0		0.3	2.0		30, 45	Gravel with Identical Diameter		2VD	G
Watts and Grilli, 2003	30		3.6	1.8		45	Glass beads, steel shots and lead shots		2VD	G
2VD : Two-Vertical Dimensional 3D : Three Dimensional PLG : Pneumatic Landslide Generator								G : Generation of Impulse Wave P : Propagation of Impulse Wave R : Run-up of Impulse Wave

Detail references

In this experimental work, 120 laboratory tests have been performed on the submarine landslide generated waves in a 2.5m wide, 1.8m deep and 25m long tank at Sharif University of Technology. Two adjustable inclined flat surfaces with a distance of 8m from each other were installed in the tank. The slope of flat surfaces is adjustable in a range of 15 to 60 degrees. One of the inclined surfaces operated as the bed for sliding down of solid blocks and another one for observation of wave run-up. Seven solid blocks with different shape, volume and thickness were used to generate tsunami waves. They had been made of steel plate with 2mm thickness. The water surface fluctuations were measured using eight pressure gauges located at the central axis of the tank. The gauges are Validyne D15 differential pressure transducers (DPD-D15).

102 tests are performed with rigid slide and 18 tests are carried out using deformable underwater slide. The deformable-landslide tests are divided into two categories. At the first group of experiments, granular materials are naturally used without any confining fabric, so after releasing of the slide, it has completely deformed and dispersed in the water body. For the second group, granular materials are confined in a very soft fabric. So, the slide behaves like a dense current and the continuity of slide will be held during deformation. These two scenarios are selected to investigate the impulse waves caused by underwater granular deformable slide and interconnected slide such as cohesive deformable slide.

The moving pattern of underwater slides is captured in experiments with a 25 frame per second digital camera. The location of mass center of slides is determined during sliding down at 0.04-second time step. The location is measured parallel to the bed slope and the S-t curve is determined where S is the slide mass center location. The u-t and a-t curves are found from S-t curve by two-step time derivation where u is the slide velocity and a is its acceleration. Based on u-t and a-t curves, the main parameters of slide kinematics, u_t and a₀ is determined.

The measured data have been used to investigate the tsunami wave pattern caused by underwater landslide. The various experimental conditions are considered to achieve an overall view of wave feature in near and far field. The main results of experiments include water surface time series recorded at eight wave gauges ST #1 to ST#8 as well as observed wave run-up.

Download Tests Specifications

Download Landslide Kinematics Data

Download Impulse Wave Data

· Test specifications