13 Elastic Wave Propagation Modeling During Exploratory Drilling …
179
a
b
Fig. 13.5 Mises stresses distribution from drill strike at time instants: a 0.0125 s, b 0.0325 s
The third segment is the movement of the wave up the bottom layer with subsequent
penetration into the island and reflection from the free surface of the ice.
We can see that the ice island plays the role of a kind of resonator. The free surface
of the ice is completely reflective, while the boundary between the ice and the nearbottom layer partially reflects the elastic waves. Since the height of the island is small
compared to its length, the vertically propagating wave experiences many reflections
in the time it takes for a horizontally propagating wave to reach the edge of the island.
This means that, possibly, with some special choice of external periodic disturbance,
the ice island is able to accumulate elastic waves. Accumulation, of course, will
occur until the beginning of the destruction of ice. Such a resonant phenomenon, if
it exists, poses a significant danger to work on such an ice platform.
If the wave propagating from the introduced point source has a large amplitude,
then it can destroy the ice. As can be seen from Fig. 13.5, such fractures will likely
be located directly above the drilling point. This is facilitated by the interference of
waves entering the island from below with waves reflected from the free surface of
the ice.
13.4.2 The Modeling of Earthquake Impact on Ice Island
The earthquake was modeled as Ricker plane wave spreading from the depth to the
surface. In Fig. 13.6, we can see the distribution of pressure (Fig. 13.6a) and Mises
stresses (Fig. 13.6b) in the instant when the earthquake wave reaches the ice island.
Analyzing the Mises stresses distribution one can determine the points where the
ice island is going to destruct.
179
a
b
Fig. 13.5 Mises stresses distribution from drill strike at time instants: a 0.0125 s, b 0.0325 s
The third segment is the movement of the wave up the bottom layer with subsequent
penetration into the island and reflection from the free surface of the ice.
We can see that the ice island plays the role of a kind of resonator. The free surface
of the ice is completely reflective, while the boundary between the ice and the nearbottom layer partially reflects the elastic waves. Since the height of the island is small
compared to its length, the vertically propagating wave experiences many reflections
in the time it takes for a horizontally propagating wave to reach the edge of the island.
This means that, possibly, with some special choice of external periodic disturbance,
the ice island is able to accumulate elastic waves. Accumulation, of course, will
occur until the beginning of the destruction of ice. Such a resonant phenomenon, if
it exists, poses a significant danger to work on such an ice platform.
If the wave propagating from the introduced point source has a large amplitude,
then it can destroy the ice. As can be seen from Fig. 13.5, such fractures will likely
be located directly above the drilling point. This is facilitated by the interference of
waves entering the island from below with waves reflected from the free surface of
the ice.
13.4.2 The Modeling of Earthquake Impact on Ice Island
The earthquake was modeled as Ricker plane wave spreading from the depth to the
surface. In Fig. 13.6, we can see the distribution of pressure (Fig. 13.6a) and Mises
stresses (Fig. 13.6b) in the instant when the earthquake wave reaches the ice island.
Analyzing the Mises stresses distribution one can determine the points where the
ice island is going to destruct.