In this paper, an attempt is made to interpret some soil physical phenomena, such as water content and shrinkage, of Kanto-loam. Kanto-loam, once air dried, has distinctly different properties from undried (natural) one. Based upon this fact, it is now postulated that Kanto-loam, in drying process, can differentiate into two groups, that is individual and massive particles, and that the individual particles have properties of undried matters while massive ones have those of air-dried ones. Kanto-loam has different values of water content and shows different phases of shrinkage in drying process. These properties are explained by mixing ratio of individual and massive particles.

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In the measurement of soil moisture under field conditions, it is desirable to cover continuously a wide range of moisture. To meet these requirements, nylon electrical resistance units and plaster blocks, introduced by Bouyoucos and Mick, are generally used. However, these resistance units still have various disadvantages.
Absorbing, blocks of high sensitivity over a wide range of soil moisture were investigated for overcoming these disadvantages. The “glass-filter electrical resistance block” was found to be most effective, and its characteristics were measured.
The glass-filter block has internal electrodes similar in principle to those of former units, as shown in Fig.1. This block furnishes a very good method for measuring soil moisture from saturation to almost wilting point. When buried in the ground, the block is durable and does not wear out. The block is adoptable, judged from the small dispersion of repeated measurement values as compared with former units, as shown in Fig.4.

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The flow through soil after precipitation, the part of which appears as surface runoff, can be divided into following three stages: 1) free infiltration observed before surface storage occurs; 2) infiltration during the advance of wet front through soil after the surface storage; 3) consequent steady state flow.
Surface runoff is closely related to initial moisture content in stages 1) and 2).
The present paper is an attempt to evaluate the effects of initial moisture content on surface runoff.
The time between precipitation and surface runoff, as well as infiltration rate, decreases as the initial moisture content increases. It follows that the causes of the decrease are the presence of entrapped air and the downward movement of the initial moisture in soil.
The auther derived the rate of surface runoff, which is a function of time, from the infiltrationtheory, and obtained the following formula:
Q= (r-K) (1-t_s/t)...(1)
where Q is the rate of surface runoff, r is rainfall intensity, K is Darcy's permeability, t is the time after beginning of rainfall, and t_s is the time between beginning of rainfall and that of surface runoff. Formula (1) agreed with the experimental data.

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A small evaporimeter with a lid was designed. Water level is measured by a pointgage fitted to the lid, water vapor and air can go out through the holes on a side wall of themeter, but rainwater can not enter.
The meter was proved to be more accurate than the conventional evaporimeter used by theWeather Bureau of Japan, and promises to be a good indicator of evapotranspiration in the field.

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Experiments and observations were carried out, by using phytotron, on the evapotranspiration which is an element to determine water requirement of crop and its seasonal changes during the crop season.
Young rice plants were bedded out into a tank filled with the soil taken from paddy rice field and evapo-transpiration was measured in each different growing stage.
The evapo-transpiration in the tank was obtained by measuring water requirement in depth and recording the daily rate of total water consumption. The apparatus used in these experiments is shown in Fig.2.
It was found that the rate of evapo-transpiration increases from the allering stage to the heading and flowering stages, and decreases in the maturing stage.
It follows from the results of these experiments that
Y=9.394 (1+T/10.581) ^1.365 (1-T/4.759) ^0.614+4.0
where Y: rate of evapo-transpiration (mm/day),
T: time (day),
origin=Maximum.

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The ladino clover was transported to the tank in a phytotron and was mowed when it attained optimum growth. The crop.was again allowed to attain maximum growth and again was mowed. Experiments and observations on the evapo-transpiration of the crop were carried out at the time of harvest.
The consumptive use of water was measured in Mariotian equipment and the measured volume was converted in water requirement in depth.
The quantity of evapo-transpiration after the second mow increased rather rapidly as compared with the first one.
It follows from the results of these experiments that both of the evapo-transpiration curves of the crop indicate monotonic increase and are Logistic curves of the form Y=K/(1+me^-at)
where Y: rate of evapo-transpiration (mm/day),
t: time (day),
K: The limit value of Y,
m; a: constants,
e: Napierian base.

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火山灰地帯の水田はその土壌のもつ特異性から一般に漏水が著しく大きい。著者らは, チュウ積砂質漏水田におけるベントナイト客土と同様火山灰質漏水田の過剰浸透を合理的に抑制するための改良方法を明らかにするために本実験に着手した。本実験においては, まず第一段階として, 火山灰土壌におけるベントナイトの透水抑制効果を低下させる因子について考察したが, さらに明らのかにした諸点をあげれば次のとおりである。
1. 火山灰質漏水田において, チュウ積砂質漏水田と同等の抑制効果を期待するためには, それの場合の5智6倍もの多くのベントナイトを客入しなければならない。
2. 火山灰土壌がチュ積土壌と相違する点は, 前者は粘土鉱物として多少ともアロフェンがあるのに後者にはそれがない。また, 前者が後者の約20～30倍も活性アルミナが多いことである。
3. 土壌-ベントナイト混合系において, 一般に分散が抑制され, S.Vは原土とほとんど変らずlooseで, 膨潤量が抑制される傾向にある場合にベントナイトの透水抑制効果が低下することがわかった。
4. 火山灰土壌とベントナイトを等量混合して18カ月間水中に分散放置した試料は一般に膨潤量が低下するが, 同様に処理したチュウ積土壌は低下しない。
5. 膨潤量が抑制される原因が客入ベントナイトの結晶格子層間が影響されるためと考え, 膨潤量測定した試料についてX-線回折を行ったところ, 層格子間には何ら影響はなかったので膨潤量の低下はベントナイトと火山灰土壌の表面的な結合のあり方によるものと推察された。
6. 従って, 火山灰土壌中でベントナイトの透水抑制効果を低下させる因子は, Fig.2並びに分散, S.Vあるいは膨潤性などを相関連させて比較検討した結果, Table1で明らかなように, 各種火山灰土壌中に共通して顕著に含有される活性のアルミナであろうと推察した。
7. そこで, Al-mont. とNa-mont. との混合系の性状並びに火山灰土壌中のアロフェン類似の試料としての合成抱水ケイ酸アルミニウムーNa-mont. 混合系におけるNa-mont. の分散性から, 推論した因子の妥当性を実証した。
以上から, 火山灰土壌中に多量に含まれている活性アルミニウムがベントナイトの透水抑制効果を低下させる因子であることが解明されたので, 今後, 何らかの簡易な処理によってベントナイトをチュウ積砂壌土と同等量程度, あるいはそれ以下で火山灰質漏水田の過剰漏水を抑制できるような改善方法を究明したいと考えている。

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Among hydraulic jumps on sloping bed, the one which begins on sloping bed and ends on the horizontal bed at downstream-case 2 of C. E. Kindsvater's classification-was experimentally studied.
1) Conjugate depth
The conjugate depth can be calculated by using the momentum equation for the jump when the pressure distribution along the sloping bed is known. Therefore, pressure distribution was experimentally obtained for various states of jump.
According to the test results, the pressure distribution was affected largely by the bed height of the entering jump from the toe of slope, z, and was expressed as a function of q/z√gz.(q: the discharge per unit width, g the acceleration of gravity)
The conjugate depth which was calculated by using the experimental expression for pressure distribution at each of the slopes 1:1, 1:3 and 1:5 agreed with test results.
And then, the conjugate relation ξ=h₁/h₂ (h₁ the depth of entering jump, h2: the tailwater. depth) may be presented as functions of the Froude number of entering jump Fr₁, z/h₁ and the bed slope, and the relation between ξ and Fr₁ which was illustrated with slope and z/h₁ as parameters agreed with Rindlaub's test results.
Because the variation of ξ lies within 5% for the change of tan a by the unity (a: the angle between sloping bed and horizontal bed), the effect of slope can be disregarded in the approximation of ξ. The calculated results which were obtained by using the experimental equation and disregarding slope effect agreed with Bradley-Peterka's test data.
2) Jump length
The jump length, which was defined as the distance from the entering jump to the end of surface eddy, was shown as a function of q/z√gz without any relation with bed slope.
3) Head loss
The velocity distribution in the jump was found by using the pitot sphere and the energy coefficient was known. And then the dissipating process of energy head was found. According to this process, it was found that most energy to be lost is dissipated before the end of surface eddy.
The relation among the head loss, bed slope, z/h₁ and Froude number of entering jump is given.

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It is well known that the overflow in a river can be briefly studied by means of an analogous electric circuit, because the differential equation of flow in the river can be approximated by a form similar to the telegraphic equation, although non-linear factors are involved.
In the present paper it is discussed that both quantities, the flow in the river and the amount of rainfall, denoted by w, will vary approximately with time v in the normalized form w=ve^1-v. It is predicted that this approximation can be deduced from a pulse-shaped model of rainfall at the basin near an equivalent river, and that the rainfall intensity and the amount of flow are related to each other with the following parameters: the distance from river source and the velocity of water and the area of the basin. Thus the anlogous correspondence between the model and the facts was attained. A practical analogous circuit and its operations are also shortly described.

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This report explains the measurement devices and the method of analysis in the model test of arch dam.
1) In the test within elastic limit of model, mercury was adopted to represent water pressure in prototype by next reasons. a) Its density is large enough (13.6). b) It does not give any concentrated load to the model. c) Loading can be made very easily. d) Strain measurement on the upstream and downstream surfaces is possible by using mercury. Fig.15 shows the devices for mercury loading.
Deflection of the downstream surface is measured in the arch radius and arch tangent directions by dial gauges (scale 1/100, 1/200 and 1/1, 000mm). See Fig.16.
In the measurement of strain on the upstream and downstream surfaces, wire strain gauges (length: 8mm, width: 4mm, resistance: 120Ω) are used. Compensating gauges are attached to active gauges, because wire gauges are very sensitive for temperature. By those gauges 4 components can be measured at each point.(See Fig.17)
2) The method of analysis was established from measured strain and stress.
If the surface stress at the measuring point is in the state of plane stress, arch, cantilever, main and shearing stresses, produced in model by mercury, are presented by equations (5-3), (5-5), (5-6), and (5-7) respectively. The coefficients between model and prototype become δ_p=147 δ_m (in deflection) and δ_p=7.350δ_m (in stress).
As the stresses for dead load are not given by model test using mercury, they are calculated by the method of analysis in uncracked cantilver. Namely, after vertical thrust and bending moment by the dead load on elevation at measuring point are calculated by epuations (5-23) and (5-25), they are computed by next equations:
δ_V'D=ΣW_{e, n}/A_n-M_{e, n}/I_n·(T_n-l_gn)...(downstream side)
δ_V'U=ΣW_{e, n}/A_n-M_{e, n}/I_n·l_gn...(upstream side)
δ_V'D and _V'U are the vertical stresses to normal for horizonta1 section. The values of measurement, on the other hand, are surface stresses of dam body. Therefore, _V'D and _V'U must be converted into surface stresses. The relation between vertical stress and surface stress becomes δ_V=δ_V' sec²φ'.φ'is given by equations (5-28), (5-32) and (5-33).

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