Textbook Notes (363,144)
Chapter 5

# soils 2B03 chapter 5.docx

3 Pages
188 Views

School
McMaster University
Department
Earth Sciences
Course
EARTHSC 2B03
Professor
Sherry Smith
Semester
Fall

Description
2B03 start of chapter 5 oct 2  determine texture by feel: we don't use this specific texture  texture is grain size distribution  can use settling rates in water; stir it up is more dense then water, float thing to determine density, hydrometer will go lower as particles fall  uses stokes law: just need to know why particles fall at different rates due to friction i.e . depends on how thick fluid is (water vs honey)  use a sieve and use that for grain size distribution  different textures have different properties (see behaviour of soils chart  well graded; lots of different sizes, well sorted means all the same size  particle density: mass of solid material/ volume of solid material  2.65 gm/cm3 is density of quartz; starting point for all soils  dry bulk density: mass over volume= mass/ volume of soil+air+water  porosity= n= volume of voids over total volume= (air+water)/(soil+air+water)  soil wetness: how much water in the soil  mass water content= mass of water content/ mass of soil  volumetric water content= volume of water/ volume of soil+ volume of voids  when asked for water content: asking for volumetric content  degree of saturation: volume of water/ volume of air  void ratio= e= volume air+ volume water/ volume soil  air filled porosity: volume air/ volume total 2B03 chapter 5  soil tension = (-) soil pressure, negative numbers and such  fig 5.12 soil water potential is pressure in potential units kilopascals (kPa) (shows range of pore sizes)  volume moisture content= when perfect saturated = porosity  sand porosity ~ 25%, loam ~ 45%, clay is like ~60%  move along diagram more negative pressure  as goes rightward, bigger pores loose water first  sand graph looses water quicker because of its larger pores  curvature of meniscuses is same for each (at each pressure shows size of pore eg at -1000 each has size pores x and under at the point)  textural influences  conductivity vs pressure  conductivity completely changes over pressure  somethings are a million times slower (note the log scale)  clay soil works better at low pressure because in sandy loam there isnt much water left to conduct, clay still has about 50% of tiny pores still filled with water  fig 5.14porous ceramic (looks like marshmellow) as the soil gets water or drier the cermatic caliprates its properties, showing the changes in pressure  use for dry soils, eg to find wilting point of plants, used in irrigation systems  figure 5.17 has little porous tip on the end (always filled with water)  when soil is at -1000, soil will try to pull water out of perfectly sealed instrument, pulling pressure (tension) is recorded  fig 5.15 neutron bulb, neutrons come out of source into the soil, when neutrons hit hydrogen, it hits about 32 it becaomes a thermalized neutron censor (finds slow ones)  wetter soils have more hydrogen therefore will have more, slower netrons will come back faster 
More Less

Related notes for EARTHSC 2B03

OR

Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Join to view

OR

By registering, I agree to the Terms and Privacy Policies
Just a few more details

So we can recommend you notes for your school.