I am PhD student in Australia working on similar material on
rehabilitated mined land. After considering numerous options, I opted
for CS229 matric sensors from Campbell Scientific. They have been used
successful on such materials here. The size of the sensors allows you
to install them in the fine material between the rock
particles/fragments. In my case I have a pair of CS229 and CS616 at 15
and 140 cm depths. CS229 costs about US$200 each, and hopefully it
fits your budget.
There are numerous water potential sensors out there. The best way to
learn how they perform is to share experiences with those who have
used them on similar material and climatic conditions. Some of the
sensors are very sensitive to temperature and mineralogy (e.g iron
oxides). Some sensors have been reported to give erroneous results or
cease logging under temperature extremes.
This is just a suggestion from another student.
Regards,
Willis
If you are limited by budget to using an Irrometer I suggest you could
install it in a wider augured hole and pack it in sand slightly finer than
the surrounding soil.
Provided rain is kept from infiltrating down the hole, ie there is only
lateral infiltration, the moisture tension reading should equilibrate with
the surrounding soil.
We make robust sensors based on the thermal dissipation principle and we
pre-calibrate them for moisture tension in the range 0-60kPa
(www.mcburneyscientific.com) . If required we can supply a version with
sensitivity optimised for the range 0-20kPa, which might suit your
situation. However it comes with built-in logger, solar charger and choice
of bluetooth or GPRS, so it won't be cheaper than the Irrometer.
I'd be interested to hear how you get on and what other suggestions you
receive.
best wishes
Terry McBurney
ROD THOMPSON
Universidad de Almería,
Dpto. Producción Vegetal,
Edificio CITE-2B,
La Cañada
04120 ALMERÍA
SPAIN
Tel: ++34 638140123
Fax: ++34 950 015939
E-mail: rod...@ual.es
Hello Luca
If you are trying to define water properties for stony soils you should be aware that the stones highly modify the water storage and transmission characteristics of the soil. This is something that is not normally taken into account but the effect could change completely the soil water response. Firstly the volume of soil occupied by stones does not storage water and therefore the volumetric water content is reduced by the volumetric stone content and secondly the hydraulic conductivity is also affected through the tortuosity factor (there are other issues but not going into them now). From our experience a stony sandy soil could behave as a clay soil for higher water tensions and at the same time when water tension is lower it can have a very high value for Ksat.
Note that calibration equations for soil dielectric sensors assume no stone content and the dielectric response is different if you have stones around the sphere of influence of the sensor.
Summing up, soil water dynamics for the fine earth fraction only will not tell you much about the soil water response for a stony soil, especially if the stone content is high. Try also to get a good estimate of the stone content and try to get a higher resolution in depth on your measurements with whatever kind of sensor you use.
Best regards,
Jesus
--
Jesus
Fernandez Galvez, PhD
Estacion Experimental del Zaidin
National
Council for Scientific Research, CSIC
C/ Profesor Albareda 1, 18008
Granada, Spain
Tel: +34 958 181600
Fax: +34 958 129600
Currently, visiting scientist at University of Reading, UK
> />
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Ajay,
Besides the sap flow you might consider measuring stem/trunk diameter change.
Joe Henggeler
University of Missouri
Portageville, MO
Best regards,
Jesus
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it now.</a
That is an interesting discussion about water in stony soils. In spite of
that Im not measuring soil water potential in stony soils. We evaluated
infiltration and saturated hydraulic conductivity (with single ring and
Guelph Permeater) in stony horizons of petroplinthite Plinthosols and
Plinthosols only with soft plintite. We are also evaluating soil water
retention curves from those soils but as in the pF 4.2 we analyzed the
water hold using sieved soil and other points of low tension (pF 1, 1.8,
2, etc) we did directly from "undisturbed" samples in stell cylinders
(some with petroplinthite inside), I ask if someone has experience in
interpreting those curves with bias caused by presence of stony in soil
water as disucssed by Jesus.
I thank in advance any help
Wenceslau Teixeira
Embrapa Amazônia Ocidental
> Links:
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> [1] http://groups.google.com/group/sowacs?hl=en
>
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I am a PhD student at the University of western australia,
investigating the ecohydrology of rahabilitated mine sites. One of my
objectives is to determine the spatial variability of saturated
hydraulic conductivity of the sites. To do that I need a method that
will aloow me to make a lot of point measurements is the shortest time
possible. To this effect I am using the well permeameter method.
However, preliminary results show that the hydraulic conductivity of
the material is very high such that a a column/resevoir (1.5m long)
filled with water will only allow me to take a total of 10 readings at
an interval of 10 secs, meaning that the column/reservoir empties
within 2 minutes.
Does any member of the group have a suggestion on how I can obtain
reliable results from this method?
I look forward to your suggestions.
regards,
Willis
este
tesQuoting terry mcburney <tmcb...@clara.co.uk>:
As an electronics technician in the UMass Amherst Civil and Environmental Engineering Department, I worked with many faculty and students and various methods of determining soil conductivity.
Shawn Kelley's "Permanent Conductivity Points" (PCP) approach to determining the electroconductivity of saturated soils in monitoring wells might be applicable to your research. Shawn's PCP design consisted of pairs of brass screws mounted an inch apart every two feet along PVC pipes within the monitoring wells. The number of conductivity points depended on the depth of the given monitoring well. Pairs of wires attached to the brass screws permitted monitoring at terminal blocks using a garden variety conductivity meter.
http://www.campbellsci.ca/campbellscientific/Catalogue/TDR100_Br.pdf
Campbell Scientific also offers a Time Domain Reflectometry (TDR) module and various probes, but they are only 30 cm long.
4$2 2EFLECTOMETER
The
TDR100 Time-Domain Reflectometer
is the core of the Campbell Scientific
Time
Domain Reflectometry system. The TDR100
(1) generates a very
short rise time electromagnetic
pulse that is applied to a coaxial
system which includes a TDR probe for soil
water measurements and (2)
samples and
digitizes the resulting reflection waveform
for analysis
or storage. The elapsed travel time and pulse reflection amplitude contain
information used by the onboard
processor to quickly and accurately
determine soil volumetric water content, soil bulk electrical conductivity,
rock mass deformation or user-specific, time-domain measurement.
Up to
16 TDR100s can be controlled using a single Campbell Scientific datalogger. A
250-point waveform is collected
and analyzed in approximately two seconds.
Each waveform can have up to 2,048 data points for monitoring long cable
lengths used in rock mass deformation or slope stability.
For years, I suggested the Tektronix 1502 series of TDR equipment, a balun and some 300 Ohm twinlead for continuous conductivity monitoring along the length of the cable. Looks like someone else finally had the same idea! Good luck with your efforts!
Dave B.
http://coweeta.ecology.uga.edu/webdocs/1/tdr.html
TDR Soil Moisture
Measurements *** Use of instrument and
interpretation of waveforms requires training ***
1) Description:
Time-Domain Reflectometry (TDR) is
a technology that was initially developed to allow service
personnel to locate damage in buried communication cables. A
microwave signal is applied to the coaxial cable and reflected by
discontinuities (breaks or shorts) in the cable back to the
source, where a video display converts the time delay to distance
and graphs a profile of the cable. The apparent distance to the
point of damage can be measured and service personnel instructed
where to dig. It was found that the apparent distance to the cable
break varied from the actual distance depending on the dielectric
constant of the surrounding soil, which is directly proportional
to soil moisture content.
Soil scientists began using TDR
technology in reverse, employing wave guides (broken cables) of
known length to deduce soil moisture via several polynomial
equations. These wave guides are generally constructed from
stainless steel welding rods, which once installed, can be left in
place indefinitely. This allows for precise, repetitive, safe, and
relatively non-destructive soil moisture measurement at almost any
sampling frequency. There are now instruments on the market
designed specifically for soil moisture measurement, e.g.
Soilmoisture Equipment Corporation (SEC) Trase instrument, which
employ automated waveform interpretation, etc. We generally prefer
to use the Tektronix Corporation 1502 series instruments, which
were designed for cable testing, due to their record of field
durability and the amenability for operator interpretation. This
interpretation, however, requires a certain amount of operator
training to minimize subjectivity and maximize comparability of
measurements taken by different operators.
*** Be certain that you are adept
at the TDR procedure before taking measurements ***
2) Project Specific Notes:
There are several methods for the
construction and installation of wave guides. Some studies employ
vertically oriented rod pairs, 5 cm apart, to which test leads are
attached directly. This method integrates soil moisture content
from soil surface to the lower depth of the rods. On some studies,
currently the gradient plots, the TDR rods are oriented parallel
to soil horizon and connected to coaxial cable extending above
ground. This method, which allows measurement of discrete soil
horizons, requires more intensive installation procedures and
detailed waveform interpretation. Currently, soil moisture
measurements utilizing the TDR technique are made bi-weekly on the
Gradient and Riparian projects.
3) Sampling Equipment:
a) Tektronix 1502 Cable Tester with
charged battery pack 4) Sampling Procedure:
a) pull on Power button on lower
right hand side of instrument panel Data from the TDR measurements are
converted to dielectric constant from the square of apparent
length divided by actual length of waveguide, then to percent soil
moisture via a polynomial equation:
% H20 = [-5.3 x 10e-2] + [(2.92 x
10e-2) (D)] - [(5.5 x 10e-4)(De2)] + [(4.3 x 10e-6)(De3)]
where: D = dielectric constant e =
exponent
|
http://geotech.ecs.umass.edu/spkelley/resume.pdf
Shawn
P. Kelley
PO Box 3373
Amherst, MA 01004
Email:
ske...@ecs.umass.edu Telephone: 413-695-1816 (H), 413-577-1242 (O)
________________________________________________________________________________________________________
EDUCATION & University of Massachusetts, Amherst, MA
HONORS Ph.D. in
Geotechnical Engineering
Civil and Environmental Engineering Department,
September 2003
University of Massachusetts, Amherst, MA
M.S.C.E. in
Environmental Geotechnology
Civil and Environmental Engineering
Department, May 1997
University of Massachusetts, Amherst, MA
B.S.C.E., Civil and Environmental Engineering Department, May 1994
GPA:
3.14 Dean's list: Fall 1993, Spring 1994
CERTIFICATIONS: E.I.T. Certified
(Massachusetts No. 15724), March 1995
O.S.H.A. 40 hr. Hazardous Waste
Training (Certification No. 9020)
Nuclear Soil Density Testing
Certified
AWARDS: William M. Boyer Civil Engineering Award ? May 1994
Civil and Environmental Engineering Department, University of Massachusetts
Amherst
Student Service Award ? May 1994
College of Engineering,
University of Massachusetts Amherst
ADSC-IAFD Academic Scholarship ?
September 2000
ADSC: The International Association of Foundation Drilling,
Industry Advancement Fund
Service Award ? December 2000
Geotechnical
Engineering Group, University of Massachusetts
Geotechnical Engineering
Fellowship ? December 2002
Geotechnical Engineering Group, University of
Massachusetts
HONOR SOCIETY: Chi Epsilon, National Civil Engineering Honor
Society Member
PROFESSIONAL Geotechnical Engineer, GeoDesign, Inc.,
Middlebury, CT and GeoDesign, Inc., Windsor, VT
EXPERIENCE July 2001?
January 2003
? Performed numerous geotechnical engineering site
inspections on projects involving shallow
foundation subgrade preparation,
soil fill placement and compaction, test pit excavating, and
pile
driving.
? Performed soil-drilling inspection on numerous projects,
particularly the State of Connecticut I-
95 New Haven Harbor Crossing
Improvements Project. Responsibilities included
simultaneously
coordinating as many as six soil-drilling crews and managing the
geotechnical
engineering inspection of each crew during the site
investigation phase of the project.
? Experience writing shallow
foundation design reports for numerous projects.
? Performed design
analysis of laterally loaded deep foundations using L-Pileplus 4.0 computer
program.
Geotechnical Engineer, Simpson Gumpertz & Heger, Inc.,
Arlington, MA
June ? August 1999
? Performed installation inspection
of permanent ground anchors (drilling and grouting) and
performed testing
inspection for the anchor-testing program of a retaining wall repair
project.
Geotechnical Engineer, TerraTech Engineering, Shutesbury, MA
June 1999 ? July 2002
? Conducted geotechnical in situ tests for
numerous engineering consulting firms
throughout New England and New
York.
SHAWN P. KELLEY 2
? Experienced in performing the following in
situ tests: Cone Penetration Test,
Piezocone, Plate Load Test,
Pressuremeter, Field Vane Shear Test, Borehole Shear
Test, Drive Cone
Penetration Test.
? Responsible for reducing in situ test data and
preparing engineering reports
Geotechnical Engineer, In Situ Geotechnics,
Inc., New London, IA
February 1996 - May 1997
? Conducted
geotechnical in situ tests for numerous engineering consulting firms.
Environmental Engineering Aide, Westover A.F.B., C.E. Dept., Chicopee, MA
June - September 1994
? Implemented a new solid waste and recycling
program for the Air Force Base.
? Provided oversight to several U.S. Air
Force environmental compliance issues.
Civil Engineering Aide,
Dufresne-Henry, Inc., Consulting Engineers, N. Springfield, VT
September -
November 1993
? Performed an engineering study on ground water for a public
water supply system.
? Participated in a traffic survey as part of a major
road intersection design project.
RESEARCH Ph.D. Candidate, University of
Massachusetts, C.E.E. Dept., Amherst, MA
EXPERIENCE Title: Detection and
Delineation of Deicing Materials in an Unconfined Aquifer via EC
Measurements
May 1997 ? February 2003
? Research involved sampling
and monitoring of ground water in Plymouth, MA as part
of a Massachusetts
Highway Department research project. Focus of research involved
methods
for field measuring of ground-water electrical conductivity and ground-water
flow.
? Performed an extensive environmental geotechnical investigation
for the UMass
Salt/Premix Storage Practices and Groundwater
QualityResearch Project in Plymouth and
Cohasset, MA. Obtained knowledge
of soil drilling operations and soil and ground water
sampling
procedures.
Research Assistant, University
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I am a PhD studet investigating ecohydrology of rehabilitated mined
land in Western Australia. I am using Theta probes (Delta T) hooked to
a Campbell Scientifc datalogger (CR1000). When I did a test run of the
system with the theta probes in their casings, I got quite variable
voltage readings ranging from -24 to about -68 mV (see attachment).
These readings appear unstable until about the 3rd and 4th readings.
What is more worrying is that when I placed two of the theta probes in
water (probes # 5 and 9) in the 2nd and 4th reading, the readings
didn't show any response. An earlier calibration of the probes using a
series of soils with different moisture contents showed an excellent
relationship between voltage and moisture content. The probes gave a
voltage reading of 1100 mV in water. However, apart from the theta
probes, the other sensors (air temp, rel. hum, matric sensors) seem ok.
Could someone please assist me troubleshooting the problem.
Regards,
Willis