|其他摘要||Characteristics study of blown sand activity is an important basic work of sand dunes hazard control, also is an important foundation of adjusting measures to local conditions and specific hazard. This study based on 214 provincial highway establish the observation cross-section, use the field observation and indoor experimental analysis methods, systemic analyze time-space distribution character of the sand materials and wind regime and blown sand activity on dry up lake-basin region of Taitema lake. The primary conclusion is as follows:
(1)The earth's surface is no water and soil take on slightly alkaline on dry up lake-basin region of Taitema lake. From A to C, particle size gradually become fine, fractal dimension gradually increase, sorting coefficient gradually from good to poor, skewness gradually from positive to extreme positive, kurtosis gradually from mesokurtic to leptokurtic. The deposition are mainly composed by very fine sand and silty sand, fine sand comes second and does not contain more than middle sand. From A to C, fine sand and very fine sand content decrease, clay and silty sand content increase. The deposition of the study area is derived from wind-blown sand, and the ways of grain transportation is mainly saltation, creep comes second at points A and B, suspension comes second at point C.
(2) During the period of observation, 6th-9th months are mainly wind months, and wind velocity decreases after 9th month. The average wind velocity is about 5m/s at point A and about 3.5m/s at point C. Wind velocity at point A is larger than point C more than 40%.Winds of 1-4m/s account for 51.65% of all winds at point A and account for 65.28% at point C. 91.50% of winds under 10m/s at point A and 92.54% of winds under 7m/s at point C. Strong wind(> 6 m/s)of point A are more than points C, under 2m/s winds of point C are more than point A, A and C are similar at 3-6 m/s winds. There is a marked change in wind velocity in a day and it can be mainly divided into: low wind speed stage at night, high wind speed stage at daytime, wind speed increase rapidly stage and wind speed decrease rapidly stage.
(3) The wind direction is relatively single at study area. Wind direction of A and C point are mainly in ENE and its adjacent direction. Except main wind-direction, WSW and its adjacent direction have higher frequency of occurrence at point A, WSW SE and SSE have higher frequency of occurrence at point C and its rule is not obvious. The aspects of average wind speed of each direction, point A are larger than C. At point A and C, the ENE direction has maximum wind speed, the WSW direction is second and other directions are small. Therefore, in this region blown sand activity is mainly in WSW and its adjacent direction, reverse blown sand activities is by accident.
(4) The average roughness value of three typical underlying surfaces of sandy desertification, saline desertification and desert-oasis ecotone at study area are 0.0048m, 0.0067m and 0.1288m, the threshold friction velocity are 0.2423m/s, 0.5374m/s and 1.1727m/s, the friction velocity of 2m high are 3.65m/s, 7.65m/s and 8.03m/s, and it is show that different underlying surface has a great influence on winderoded dust. In this region, underlying surface of sandy desertification is easily winderoded dust, hardened surface of saline desertification and sparse vegetation of desert-oasis ecotone can effectively prevent wind erosion.
(5) Characteristics of blown sand in different underlying surfaces have significant difference. Total sand transport shows A>>B>C. The aspects of sand flow structure, the sand transport flux of point A and B decreased with height by power function, the sand transport flux of point C decreased first and then increases with height by polynomial function. The sand transport flux of point A and B are mainly distribute within 20cm and 50cm high from the earth's surface, them are account for over 77%and 60% of the total sand transport flux in observed altitude. The sand transport flux of point C is average in each high. The aspects of characteristics of Aeolian transport particle size distribution, from point A to C, the mean grain-size is decreases and the sorting coefficient becomes poor and the mechanical composition of sand gradually changed from mainly very fine sand to silty sand at each heights. In the vertical direction, with the increase of height, the mean grain-size is decreases, the sorting coefficient gradually increase, fine sand and very fine sand content decrease, clay and silty sand content increase. The skewness is gradually from positive to extreme positive and kurtosis is gradually from mesokurtic to leptokurtic.|