(1) 湿田粘質土壌は一般に高い含水量, すなわち, 含水比75～81%のもとでキ裂を発生し, その発達は長時間に及び, その停止は他土壌に比べ低い水分条件で起る。
(2) キ裂発生後は表面蒸発に内部蒸発が加わり, 内部蒸発はキ裂幅に比例して蒸気圧コウ配の増加による蒸発量の増大となるから全蒸発量はキ裂が発生しない場合より大である。
(3) キ裂平均間ゲキ比と含水比との関係は次のとおりである。
1/n・ν_f/ν/V_f/V= (1-e-a/w)
(4) 浸透径路分類系における (イ),(ロ),(ハ),(ニ) においてほ浸透量Qはほぼ次の関係をとったが.(ホ) は例外的に大である。
logQ=a+b (1/n・ν_f/ν/V_f/V)
(5) キ裂の増大とともに側方浸透量の鉛直浸透量の割合が急増する。
(6) キ裂による浸透の経年変化は, 初年度はその浸透量はA, B, C各部ともこの順に大で, 植付け準備期, 水稲生育期を通じてその差なお大であり, 4年後においてA, C部分の差は縮少するが, 両期ともキ裂発生前同期の浸透量の最大値より若干大である。なお本研究は昭和31年度文部省科学研究費によるものであることを付記してここに深甚なる謝意を表する。

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In this experiment the authors indicate, using Wagner's pots, that physical and chemicat properties of paddy soil are closely related to plant growth and vertical percolation.
Vertical percolation has an effect of decreasing the concentration of reducing substances and increasing the value of oxidation-recuction potential. The root of rice plant accelerates leaching of iron and calcium compounds and increases the size of water-stable aggregates of soil. The yield in nonpercolation plot is inferior to that in percolation plot. The difference between the two plots is due to changes in soil properties.

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This study aimed at the principles underlying the infiltration of water into dry sand and the permeability in the ensuing percolation stage after the wetting front has reached the bottom of sand column. The relations between the rate of water entry and time were examined by the equation of infiltration:
q=K_I (1+H/y) where, q: the rate of water entry in cm/sec; H=h₀+h_K; h₀: the depth of top water in cm; h_K: pressure deficiency of the water film at the wetting front in cm; y: the depth of wetting front below surface in cm.
Air-dry sand and glass particles were packed to uniform apparent density in transparent tubes, 5 cni in diameter.
in the infiltration stage, a constant depth of water was maintained at the top of soil column by means of a Mariotte tube and the rate of water entry (q) was measured. The depth of wetting front below surfa'ce (y) was also recorded. In the ensuing percolation stage, the rate of flow and the distribution. of hydraulic pressure were measured.
From these data the rate of water entry (q) was plotted as a function of the length of infiltration zone (y). Then the permeability coefficient of infiltration stage (K_I) and the pressure deficiency of the water films at the front of infiltration (h_K) were found. Results:
1. Water saturation ratio during infiltration reached nearly 100% and did not vary with depth.
2. The equation of infiltration q=K_I (1+H/y) agreed with the experimental data.
3. Kp, coefficient of water per eability in the second stage (percolation), was equal to K1, that in the first stage (infiltration).
4. The value of air pressure in front of the wetting front was nearly equal to the atmospheric pressure.

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From the second law of motion, the author has derived equations of the viscous flow of incompressible fluids through porous media from macroscopic point of view, under the assumption that the fundamental hydrodynamic relations between stress and rate-of-strain for viscous incompressible fluids are also satisfied by the fluids in pores and that the porous media are saturated, isotropic, and geometrically stable at a constant temperature.
An important point for consideration of macroscopic motion is its relationship tomicroscopic one. Such macroscopic quantities as velocity, pressure, etc. are, therefore, directly defined from the' corresponding microscopic ones from the standpoint that such physical quantities should be invariant in transformation; and the quantities thus defined are supposed to be analytical throughout the space through proper conception in order to render the subject amenable to exact mathematical treatment, though the microscopic ones defined only within the effective pores but not within the solid particles.
The equations of macroscopic motion derived on the basis of the above considerations involve inertia terms which have never been derived from the Navier-Stokes equation, and drag force terms by which the concept of drag in percolation flow is to be physically clarified ; but, on the other hand, they do not contain the so-called macroscopic viscous term, which cannot exist essentially, as shown in this paper. Moreover, it should be noted that the quite natural con equence that the drag force consists of viscous drag and pressure drag as shown here has never been verified theoretically and has been recognized even incorrectly, and a deeper exploration will result in more theoretical derivations of Darcy's or Forchheimer's law and, necessarily, also of “permeability”, clearing up the role of these in the fundamental equations.

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一般にベソトナイトが電解質溶液と作用すれば蒸溜水の場合の膨潤量よりも減少する。塩化物溶液の種類一膨潤量の関係をまずイオンの解離度からみると, 1規定の場合は1価イオンについては解離度が大きいほど膨潤量も大きいが, 2価イオンの場合はそのような関係はみられない。また, 1規定の濃度でも解離数が小さいと膨潤速度がおそく膨潤量も大きく蒸溜水とか濃度の極めて薄い溶液についての膨潤傾向に類似しており, イオン量によって膨潤量が影響されていることをしめしている。次に溶液濃度一膨潤量の関係をイオン半径 (水和能の大小) 並びにイオン化傾向 (反応順序) からみると1規定濃度においてはFig. 3のNaの特殊な挙動を除いてはベントナイト並びにカオリナイトもイオン半径 (1価, 2価ともに) の小さいものの順に (水和性の大きいものの順に) 膨潤量が少なく, イオソ化傾向の大きいものの順に膨潤量が多い。従って1規定溶液のように濃度の濃い場合は水和能が逆にdehydrationの働きとなっているものと推察される。このことは水洗いによるイオン溶脱処理の場合の膨潤量の復元化が, イオソ半径の小さいものの順に大きいことからも明らかである。さらに各種溶液濃度とベントナイトの膨潤量との関係は, 一般に溶液濃度が濃くなるほどその膨潤量が抑制されるが, 一方固定格子型であるカオリナイトの膨潤量は溶液の濃度によウてはほとんど変化しないことが明らかとなった。
ベントナイトとカオリナイトは置換容量の差違はあっでも1規定濃度では両者ともほぼ同じぐらいの膨潤量の値を示している。従って伸縮性構造をもち, 内, 外両膨潤を行なうベントナイトの膨潤量を外部膨潤のみを行なうカオリナイトの膨潤量と比較した場合, その差が濃度変化におけるベントナイトの伸縮性結晶構造による内剖膨潤量であるのではないかと考えられる。しかしこれらの関係についてはさらに結晶構造上から詳細に考究したければならないげ

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ベントナイトの膨潤はその申に含まれているモンモリロナイトの層格子間に水分子をとらえて層格子間が伸長しその結果著しい膨潤量を示すものと説明されている。第1報の結果によれば, 膨潤量は溶液の種類と濃度差によってそれぞれの特性に応じて抑制され, また, 同一規定の溶液でもその処理の仕方によって異なっている。一方イオン量からみると70～90me/100g付近で最大膨潤量を示し, その前後で著しく膨潤が抑制されている事実から, 溶液中でのcatignの膨潤特性にあたえる影響の極めて大なることが明らかとなった。本報においては, 以上の関係を主として粘土鉱物の結晶構造上から明らかにするために, X線回折, X線写真, ならびに化学分折等によって詳細に検討した結果, 膨潤は層格子間がex。pansionして膨潤する内部膨潤 (intra-micellar swelling) よりも外部膨潤といわれる粒子間膨潤 (inter-mi-Cellar swelling) の顕著に多いことを指摘すると同時に内部膨潤量と外部膨潤量の差違を定量的に検討した結果, 最大膨潤時においては外部膨潤が内部膨潤に比べて10倍程度多いことが明らかとなった。なお溶液濃度によって敏感に変化する膨潤量は外部膨潤量であって極めて濃い濃度溶液以外には内部膨潤は影響をうけないこと, また, 濃い溶液で処理して膨潤が抑制されたベントナイトでも乾燥させ後に蒸溜水を吸収させた場合は内部膨潤は完全に復元し比較的膨潤量が多いこと等も明らかにした。なおこの場合の膨潤量は直接溶液を吸収させた場合のそれに比べて多少多いので, ある程度の外部膨潤も含まれているものと推察される。従って以上, cationのみを対象にした濃度と膨潤特性の実験結果を総括的に検討してみると, 実際漏水田へ客入されたベントナイトの膨潤特性は水田のカンガイ水中のcation濃度 (実際はもっと複雑ないろいろな因子によって膨潤が影響されるが) の程度では, 施用したベントナイトの膨潤性は失われることなく充分膨潤性を発揮できるものと推察される。(短期日の室内実験とcationのみを対象にした濃度試験の結果からの考察であって, 自然状態で長年にわたる場合の膨潤特性の場合ではないので, それらについてはおって報告したい)。

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Groundwater is a very important source of irrigation and city, water supply. Scientific researches of available discharge of groundwater are indispensable in their exploitation. The velocity and direction of groundwater stream are very difficult to fathom. The methods hitherto used for this purpose are as follows:
(i) measurement of the gradient of groundwater level using pipes or wells;
(ii) tracing of groundwater labeled with salt, fluorescent substances, or radioisotope solution;
(iii) electrical or seismic exploration.
The method (ii) is very common but several hours are required even in the measurement at only one point.
The author studied a new method of the measurement of the velocity and direction of groundwater stream by means of porous pipes driven in the ground, and found that this method could save much time.
(a) The relation between U₂ (velocity of stream in the inside of the pipe) and U₂ (that in the outside of the pipe) was analyzed as follows:
U₂=U₁2_k2/k₁+k₂=2U (k₂≥k₁)
k₂=equivalent of the coefficient of permeability corresponding to the seepage through the holes of the pipe,
k₁=coefficient of permeability of the ground.
(b) The direction of groundwater stream in the inside of the pipe is perfectly coincident with that in the outside of the pipe.
(c) The velocity of groundwater stream is obtained by the measurement as is indicated in Fig. 4.
R₁, R₂: fixed electric resistances;
R₃, R₄, R₅: variable electric resistances;
E₁, E₂: sources of electricity;
S₁, S₂: switches;
A: source of heat;
B: pickup (thermister);
Am: ammeter;
G: galvanometer.
The velocity is calculated by the formula
U1=KL/2T
U₁: velocity of groundwater stream;
L: distance from source of heat to thermister;
T: time of the movement of heated water from source of heat to thermister;
K: coefficient.

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Flap gate is most widely used for the purpose of water control in reclamation land. In this study, its discharge characteristics were analyzed in two-dimensional efflux. First, the efflux from a gate was divided into submerged and free-jet effluxes, and the discharge coefficient was determined experimentally for flap gates with different values of unit weight. Next, the relation between the inclination of flap gate and head water and tail water depths was obtained.

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This report is the result of a runoff analysis by the infiltration method in a loam upland covered with volcanic ashes. In this basin the infiltration capacity is large, but the subsoil is not so permeable as the surface soil. Therefore, at the time of heavy rainfall, the infiltration capacity is much influenced by the maximum infiltration rate of subsoil. Moreover, when the ground water level is raised up to the ground surface by heavy rainfall, the area without any infiltration capacity increases to occupy a large percentage of the basin.
On these conditions, the authors calculated the runoff at the time of the typhoon No.22 in 1958 when the rainfall amounted to 280mm. The values calulated by the following methods coincided with the measured hydrograph.
(1) In regard to the movement of surface soil water, the authors assumed such formulas as follows:
dM/dt=-cM, M=M₀e^-ct, f=fc+qi, qi=K(M-M)
where, M: excess moisture content of surface soil over the field capacity;dM/dt: the rate of M moving into subsoil; M_o: maximum value of M; t: time from M_o to M; f: infiltration capacity; f_c: maximum infiltration rate of subsoil; q_i: seepage rate from surface soil that provides the source of interflow; M: the minimum value of M when q_i first appears; c and K: constants.
source of interflow; M: the minimum value of M when q_i first appears; c and K: constants. The infiltration capacity before reaching M_o is very large. In the intermisson between rainfalls themoisture in the surface soil moves down into subsoil, and the infiltration capacity is recovered. The condition corresponding to M_o usually takes place before the surface soil becomes saturated. This is be-cause the ground surface is undulatory, and the excess water in surface soil is easily discharged by seepage.
(2) In case of heavy rainfall the channel runoff in the basin floods. Therefore, the infiltration method is to be modified as follows:
i=f+re re=ΔS+
qs=ΔSf+ΔSe+qe ΣΔSc=Sc qe=K. Scm
where, i: rainfall intensity; re: rainfall excess;ΔS: the rate of surface detention; S: surface detention; q_s: surface runoff; ΔS_f: the rate of flooding storage; ΔSc: the rate of channel storage; S_c: channel storage; q_c: channel runoff; K and M: constants.
(3) The runoff from each part of the basin has a time lag in concentrating at the end of the basin. The time lag is influenced by many factors, and the authors assumed here as follows:
T=K.Q^-e
where, T: time lag; Q: discharge; K and c: constants.

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As an experiment on the mechanism of sedimentation in reservoir through tractional process, a dam, 20cm in height, was constructed across a rectangular channel having a uniform gradient (i_B=0.057), and mixed sand (d_m=1.07mm) was poured from the upstream side together with water at a constant rate of flow (q=56.66cm³/sec) by means of an automatic sand-feeder at the following ratios: q_B1=0.277cm³/sec, q_B2=0.518cm³/sec, and q_B3=1.012cm³/sec.
The accumulation of sand and the appearance of water surface were observed. A study of these data from the hydraulic standpoint and an analysis of the mechanism of sorting as well as general conclusions obtained from them will be reported subsequently.

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Based on the results obtained from a series of experiments on the mechanism of sedimentation in reservoir through tractional process, an investigation was carried out, chiefly from the hydraulic standpoint, on the rate of sediment transportation on sand dunes, on the relation between the rate and tractive force, and also on the gradient of sediment surface.
An analysis of mechanism of sorting and general conclusions will be reported subsequently.

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As an experiment on the mechanism of sedimentation in reservoir through tractional process, a dam, 20cm in height, was constructed across a rectangular channel having a uniform gradient (i_B=0.057), and mixed sand (d_m=1.07mm) was poured from the upstream side together with water at a constant rate of flow (q=56.66cm³Isec, cm) by means of an automatic sand-feeder in the following ratios: q_Bi=0.277cmVsec, cm; q_B2=0.518cm³/sec, cm; and q_B3=1. 012cm³/sec, cm. Conditions of sand accumulation and the changing appearance of water surface were observed each time. Based on the results of the, experiment, investigations were carried out, chiefly from the hydraulic standpoint, on the rate of sediment transportation on sand dunes, on the relation between the rate of sediment transportation and tractive force, on the gradient of sediment surface, and also on the analysis of the mechanism of sorting.

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