Study On The Internal Structure And Surface Fracture Characteristics Of River Ice

With the rapid development of the global economy and technology.Water conservancy,water transportation,ice and snow entertainment in the cold area have had a great impact on people’s production and life.Freezing is common in rivers,lakes and some sea areas in north China.The presence of ice layer weakens the exchange of substance and energy between the atmosphere and water,and has a certain impact on the local microclimate and the ecological environment under the ice.At the same time,it will affect the safety of water conservancy and transportation projects and ice and snow entertainment activities in the cold region.If the situation is serious,it will cause ice disasters of different degrees and threaten the safety of human life and property.Therefore,it is of great significance to research on the characteristics of ice for both ice environment and ice engineering.The internal structure of the ice and the surface fractures are the basic structural features of the ice itself.The internal structure of ice reflects the "skeleton" structure of ice,which determines the thermodynamic and optical properties of ice.The basic characteristics of ice surface fracture are the foundation and key to explain the ice expansion force and to deal with the damage of the ice slope protection.Therefore,this paper carried out an experimental study on the internal structural characteristics of the ice in Yellow River,Wuliangsuhai and Liaohe Shenyang Shifosi reservoir and the surface fracture characteristics of the ice in the Liaohe Shenyang Shifosi reservoir.Based on the observation of ice internal structure,the relationship between ice velocity and crystal structure was obtained for the first time by using Doppler velocimeter and natural channel velocimeter.The influence of freezing environment on ice internal structure was preliminarily analyzed,and the relationship between ice density and mud content in the ice under different crystal structures was discussed.At the same time,this paper also carried out an experimental study on the ice surface fractures of Liaohe Shenyang Shifosi reservoir,and preliminarily discussed the effects of topography and landform on the fractures and the relationship between fractal dimension and the fractures density.Experimental study on the internal structure of ice shows that:(1)The distribution of ice crystal structure along the depth direction is different at different sampling points in the Yellow River.There are few single columnar ice and granular ice,which are mainly characterized by the alternation of granular ice and columnar ice,while the ice crystal structure of Wuliangsuhai and Liaohe Shenyang Shifosi reservoir is a stable columnar ice structure.(2)The flow velocity under ice has a certain influence on the structure type of icecrystal.The proportion of columnar ice in the ice layer to the whole ice layer decreases with the increase of the flow velocity under the ice,and finally tends to be stable.(3)The variation of ice equivalent grain size is different at different sampling points of the Yellow River,which is mainly related to the type of crystal.The change of equivalent grain size of granular ice crystal is not obvious along the depth direction.The equivalent grain size of columnar ice crystal increases gradually along the depth direction.The size of ice crystal alternating between granular ice and columnar ice fluctuates continuously along the growth direction of ice thickness,but in the same sample,the equivalent grain size of columnar ice is always larger than that of granular ice.The equivalent grain size of ice crystal in Liaohe Shenyang Shifosi reservoir increases with the increase of ice thickness along the depth direction,and is larger than the average size of equivalent grain size of ice crystal in Yellow River.(4)The C-axis distribution of ice crystals in the Yellow River is unstable.The C-axis orientation of the granular ice crystals is randomly distributed in space,but it is basically a large ring shape.The C-axis orientation of the columnar ice is almost horizontally arranged,and there are two azimuth angles.The C-axis distribution of some sampling points in the Yellow River has a fan-shaped distribution,which shows the characteristics of ice-flower ice,indicating that there are not only granular ice and columnar ice,but also ice-flower ice in the Yellow River ice.The distribution of C-axis of ice crystals in Liaohe Shenyang Shifosi reservoir is very stable.There are always two dominant zones in horizontal azimuth.Along the depth direction,the distribution of C-axis is more and more stable,and the growth direction of ice gradually tends to level along the ice thickness direction.(5)There are three typical bubble forms in the ice of Liaohe Shenyang Shifosi reservoir,which are spherical,vertebrate and linear granular.The variation range of bubble content and equivalent diameter in the ice of the Yellow River is larger than that of Liaohe Shenyang Shifosi reservoir,but the equivalent diameter of bubbles in the surface layer of both of them have a tendency to increase gradually from 0 to 10 cm.After 10 cm,the overall trend of bubble content and equivalent diameter in the ice is gradually decreasing.However,due to the frozen environment,the bubble content and equivalent diameter in the bottom of ice layer of the Yellow River simpling points will increase suddenly.(6)The ice density and the mud content in the ice of the Yellow River fluctuate greatly along the direction of depth,and there is no certain distribution rule,different sampling points vary in different ranges.The variation range of ice density and mud content in ice of Liaohe Shenyang Shifosi reservoir is relatively small compared with that of the Yellow River,and the ice density gradually decreases along the depth direction,but the fluctuation range of the mud content in ice is relatively large along the depth direction.At the same time,the mudcontent in the surface layer of 0-5cm is significantly greater than that in the depth of 5-33 cm.(7)The mud content in ice is the reason for the change of ice density.The ice density of both granular ice and columnar ice increases with the increase of the mud content in ice,but the mud content in granular ice is larger than that in columnar ice.Experimental study on ice surface fractures show that:(1)The topography and landform will have a certain impact on the density of fractures on the ice surface.(2)The fractal dimension increases with the increase of fractures density on ice surface.