作者Jman208 (→ 171G8)
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标题[试题] 95下 李达源 环境土壤物理学 期中考
时间Mon Apr 21 22:04:19 2008
课程名称︰环境土壤物理学
课程性质︰探讨土壤的结构与质地如何跟空气与水作用
课程教师︰李达源
开课学院:农学院
开课系所︰农化系第一类群组必修
考试日期(年月日)︰Apr. 20, 2007
考试时限(分钟):两节课,100钟
是否需发放奖励金:是
(如未明确表示,则不予发放)
试题 :
1. Please define the following term in a few sentences: (15%)
(a) Particle size distribution of soils
(b) Total porosity of soils
(c) Pore size distribution of soils
(d) Soil crusting
(e) Aggregated soil structure
2. Distinguish among the following terms: reference state of soil water
potential, matric potential and solute potential od soil water. (9%)
3. Find the total potential head components at points A and B in the
following equilibrium system consisting of (16%)
(a) A salt solution of relative humidity of 0.65 in a closed chamber next
to a soil sample at T = 27C.
(given surface tension of water = 72 dynes/cm, R = 8.314 J/K mol)
┌──────────────────────────┐
│ │
│ │
│ │
│ │
│ │
│ │
│ │
│ A B │
│ │﹌﹌﹌﹌﹌﹌﹌│ │﹌﹌﹌﹌﹌﹌│ │
│ │ Solute │ │ Solute │ │
│ │ │ │ │ │
│ └───────┘ └──────┘ │
└──────────────────────────┘
(b) ↑ ┌───┐ ← Soil sample
│ │ │ A (no evaporation)
│ ┌─┴───┴─┐
50cm │ └──┬─┬──┘← Porous ceramic
│ │ │
│ │ │
↓ │ │
B │﹌﹌﹌│ │ │
│ │ ← free solution │ │
└┬─┬┘ S = -200cm │ │
│ │ │ │
│ │ │ │
│ │ │ │
│ │ │ │
│ │ │ │
│ ╰────┬──────╯ │
╰──────┴────────╯
↑ membrane impermeable to solutes,
permeable to water.
4. Describe what information related to soil water is measured or prepared by
the following instruments. (12%)
(a) Tensiometer
(b) Thermal couple psychrometer
(c) Neutron probe
(d) Time Domain Reflectometer (TDR)
5. The accompanying data were obtained with tension plate and pressure plate
extraction devices from two soils of unknown texture. (12%)
────────────────────────────────
Suction head (cm) Volumetric water content (%)
────────────────
Soil A Soil B
────────────────────────────────
0 52 44
10 52 44
20 52 43.9
50 51 38
100 48 22.5
300 32 12.5
1000 20 7
10000 13.5 5.2
20000 13 5.1
100000 12.4 4.9
────────────────────────────────
(a) Sketch the two soil moisture characteristic curves.
(b) Estimate the bulk density, assuming that the soils do not swell or
shrink.
(c) Estimate the field capacity and the volumetric water content at
wilting point.
(d) What are the likely soil textures of soil A and B and explain why?
6. A mercury manometer tensiometer is inserted 100cm below the soil surface
into a region of soil with matric potential head h = -50cm. The mercury
reservoir has a free surface 10cm above the soil surface. Calculate how
high above the free mercury surface column will rise at equilibrium?
(ρHg = 13.5g/cm^3) (10%)
7. A vertical saturated soil column of height 25cm has 10cm of water ponded on
it at t = 0. Four hours later the height of weater ponded has dropped to
5cm. What is the satureated hydraulic conductivity of this soil? (6%)
8. A long soil column (101cm) containing 100cm of sand of saturated hydraulic
conductivity 10cm/hr has a thin caly lens (1cm) of saturated hydraulic
conductivity 0.1cm/hr located somewhere inside of it. (10%)
(a) What is the effective saturated hydraulic conductivity of the entire
column?
(b) If the clay lens is on the bottom, what is the flux through the column
if 10cm of water are continously ponded on the top? What is the
pressure at the sand-caly interface?
│﹌﹌﹌﹌│
│ │10cm
├────┤
│ │↑
│ ││
│ sand ││
│ ││ 100cm
│ ││
│ │↓
├ --- ┤←─ P = ?
│ clay │1cm
└────┘
↓
J = ?
9. A capillary tube of r = 0.1cm radius and L = 10cm length has a hydraulic
head difference of 10cm across it. Calculate the discharge Q in cm^3/sec
and the flux in cm/sec through the tube. How many tubes of r = 0.01cm
radius and L = 10cm length with the same hydraulic head gradient are
required to produce the same discharge and what is the flux through such a
network? (viscosity coefficient of water ν= 0.01g/cm/sec) (10%)
-----------------------------------考试到此结束------------------------------
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1F:→ Jman208:然後这篇直接 repost 上篇居然还比较多 XDDD 我惑了 04/21 22:04
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