気泡排除を自動化したテンシオメータと平衡時間

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タイトル別名
  • Tensiometer System with an Automatic Air Bubbles Elimination and Response Time
  • キホウ ハイジョ オ ジドウカシタ テンシオメータ ト ヘイコウ ジカン

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A tensiometer system with automatic air bubble eliminatiion is assembled by using two rotary switches. When air bubbles develop in the system for a period of few days, by controlling the electromagnetic valves and bellows pump, air exhausted water could circulate in the system for a few minutes through the connecting tube and air bubbles are easily removed to the outside of the suction measuring part.<BR>The response time is less than five minutes for the case of some measurements on disturbed Kanto loam surface soil (Light clay).<BR>At the moment of switching from one to next, degree of equiribrium of the soil moisture suction in the next port reached to 90%. The readings of this tensiometer were in good agreement with the readings of the tensiometer with a mercury manometer inserted at the same depth in the soil tank.<BR>The response time of the tensiometer is simulated numerically with the water flow equation in a finite circular cylinder which considers unsaturated hydraulic conductivity of the soil, a contact resistance and effective surface area between the soil and a porous cup.<BR>These results are compared with that of the modified Richards equation (1949) containing a contact factor between the soil and a porous cup. When the difference of initial suction and total discharge through the cup is small, the results of two methods agree well with each other. On the other hand, when the suction difference and total discharge are large, the two methods do not coincide with each other.<BR>So the important factor govering the response time for the case of a small suction difference through the cup as this tensiometer, is not the hydraulic conductivity of the soil but the degree of contact of the porous cup with soil.

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