堆積機構の基礎的研究(その2) : 堆積粒子移動の限界流速(續)
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This paper mainly describes the results or experiments on "proper critical velocity" and the traction of sedimentary particles under different conditions, the theoretical relationship between proper critical velocity and settling velocity, and the geological implications of these., ("Proper critical velocity" is the mean value of velocities of currents acting at the bottom and top portions of a particle to start the movement of that particle)., Concerning the above-mentioned subject, the writer obtained the following results: (1) If the sedimentary bed has a smooth and horizontal plane, the proper critical velocity "Vp" is proportional to d^n, namely, in the case of Vpr and VpII VpI=k_1d^<nI> VpII=k_2d<nII> (cf., part 1), Where VpI is Vp to a single particle, VpII is Vp to the multiple particles, d is the diameter of the particle, k_1・k_2 and n_I・n_<II> are the constants as follows at l0℃; d<0.,14mm.,.,.,k_1=3700 k_2=360 n_I=2.,2 n_<II>=1.,8 0.,14<d<1.,3.,.,.,k_1=150 k_2=210 n_I=1.,5 n_<II>=1.,6 1.,3<d<6.,7 k_1=35 k_2=65.,.,.,n_I=0.,8 n_<II>=1.,0 6.,7<d.,.,.,k_1=31 n_I=0.,5 (2) When the particle size is fixed, Vp varies with the the density G of the particle as follows, Vp=K (G-1)^β K and β are the constants, which will be given as K=1.,1 and β=O.,65, respectively, for the given size of particles, 0.,14<d<1.,3mm., However, a grain such as the fragment of a shell has a comparatively small Vp for its d and G, as it has a larger form-drag., (3) When the particle size is fixed, Vp is proportional to the roughness dr (namely the granularity of the bottom) as follows; Vp=k_1d^<nI>+(k_2d^<nII>-k_1d^<nI>) dr/d where d>dr., (4) Vp and settling velocity W are both given by the discontinuous function of d, and if d is fixed, the value of n in Vp is equal to it in W., (5) When the concentration of particles increases, Vp decreases but W increases., These results are important as factors in determining the size distribution of sediments, and its discontinuity.,
- 日本地質学会の論文
- 1954-02-25
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関連論文
- 堆積機構の基礎的研究(その4) : 粒子の堆積と運動(續)
- 堆積機構の基礎的研究(その3) : 粒子の堆積と運動
- 堆積機構の基礎的研究(その2) : 堆積粒子移動の限界流速(續)
- 堆積機構の基礎的研究(その1)