The Physical Model Test Study On The Motion Characteristics Of Submarine Landslide Triggered By Earthquake

In order to alleviate the domestic energy shortage,improve the national energy strategy and adjust the economic structure,China will make great efforts to develop and utilize the undersea oil and gas resources and build a large number of undersea working platforms.At the same time,submarine landslides with characteristics of high speed,long distance and strong impact may occur frequently,which will damage submarine engineering facilities and cause irreparable economic losses or even casualties.Research shows that earthquake is the most important factor to trigger the instability of submarine landslide.Therefore,it is of great practical significance to study the motion process and dynamic characteristics of submarine landslide triggered by earthquake.This study can provide scientific basis for the construction and maintenance of Marine engineering and protect the safety of coastal cities and improve the living environment of human beings.In this paper,the motion characteristics of submarine landslide triggered by earthquake are studied by means of physical model test method.The self-made test equipment is used to carry out multi-group model test under different test conditions.The test in this paper not only reflects the underwater environment of submarine landslide,but also can simulate the occurrence of earthquake.A variety of measuring instruments were used to enhance the reliability of the results.The research contents of this paper include the macroscopic phenomenon of submarine landslide movement triggered by earthquake,the study on the velocity of submarine landslide,the stress analysis of submarine landslide,and the factors affecting the characteristics of submarine landslide movement.The motion law of submarine landslide triggered by earthquake is obtained and the following conclusions are obtained.1.The motion of submarine landslide is a complex movement process of the interaction between water and soil.The landslide body flows in two layers,with a high density layer(dense flow)at the bottom and a low density layer(suspended flow)at the top.The landslide body is in the shape of cloud,with the head uplifted and the tail flat.In the process of movement,the landslide body is continuously eroded and deposited.The landslide body can be transported for a very long distance by virtue of inertia and "water skiing" effect.2.In the model test,the velocity of the landslide above the slope is not uniform.Generally,the initial velocity is large,and then it is reduced by the action of water resistance,and then it is in a state of fluctuation,with a range about 13~18cm/s.The average velocity is about 15cm/s.The model landslide body was converted into a real landslide body with a geometric similarity ratio of 1000:1,with an average velocity of 4.8m/s.The velocity decreases gradually after the landslide body moves to the horizontal direction.3.The strain value of the pore water pressure sensor in the landslide model can determine the critical point of sand liquefaction.The strain value under the impact force is measured and calculated by the earth pressure sensor,and the impact force is calculated.The larger the instantaneous velocity of the landslide,the greater the instantaneous stress generated by the impact sensor.In the experiment,the maximum instantaneous stress generated by the model landslide body is 1.55 kPa.The model landslide body was transformed into a prototype landslide body with a geometric similarity ratio of 1000:1.The impact stress was up to 1.55 MPa at a water depth of 1000 m.4.With the increase of clay content of landslide,landslide in-stability is more likely to occur,the reaction between soil and water becomes more violent,the plastic rheological property of landslide becomes more obvious,but the velocity of landslide becomes lower.With the increase of vibration frequency,the landslide is more prone to instability,and the volume of low-density layer becomes larger,the motion speed becomes larger.With the increase of electrolyte concentration in seawater,the sliding force becomes larger,the movement speed becomes faster and the migration distance becomes further.With the increase of slope angle,the volume of landslide becomes larger,the movement speed becomes faster and the migration distance becomes further.