chapter 4: temperature inside the landfill

Injection records were available only through Day 700 so confirmation of the relationship was
possible from Day 150 to Day 700 only. The injection events after Day 700 were identified using
the temperature drop events at an injection well.
Identification of relevant temperature drop events at the injection events as well as
monitoring locations was to be accomplished before verifying the relationship between the
injection and temperature drop. A temperature drop (T-drop) event may be defined as a
significant drop in temperature reading of the sensor by external influences like moisture arrival
and not by internal aberrations of the sensor. After the events were identified, an attempt was
made to relate those to the injection events and hence to the moisture arrival.
Initially, a statistics test was used to indicate significant drop in temperature. The t-test
was used for this purpose. The t-test basically examines the means of two populations before and
after a change in the conditions. The prerequisite conditions for t-test are: the data set should be
normally distributed or should consist of more than thirty values. The formulation for t-test can
be expressed as follows:
_
T
t−15
If,
Then,
_
p
_ _
t+ 15 < T t−15
T
_ _
= t
t − test(
T t+ 15,
T −15)
Where T t+
15 is the mean of the temperature readings over fifteen days after the time t,
is the mean of over fifteen days before the time t and p (or probability value) of the t-test is
27
(3-4)
(3-5)