In traditional soil mechanics, much research has been
done on water-saturated soil and dry soil. Recently, more focus has
been placed on unsaturated soil, which involves the soil zone above
the ground water table. It is important to note that the behavior of
unsaturated soil is not consistent with the principles and concept of
traditional saturated soil mechanics. The differences in the behavior
and characteristic between saturated and unsaturated soils have become
a concern in geotechnical field.
Cone penetrometer (CPT) and Pre-bored Pressuremeter
(PMT) have become a popular in situ testing device for subsurface exploration
in United States. Both instruments are capable of giving estimates of
in situ soil properties such as undrained shear strength, friction angle,
and modulus of elasticity for the design of various foundations. Most
of the developed methods to interpret the CPT and PMT results are focused
on saturated soil. However, it is often that during testing layer of
unsaturated soil is encountered. Since the behavior of unsaturated soil
is different from saturated soil, there exist a need to develop a method
to interpret CPT and PMT results for unsaturated soil. In order to develop
a new method to interpret the CPT and PMT results for unsaturated soil,
significant test results are needed. Although, in situ test results
can be obtained economically and easily, they are not practical for
the development of the method to interpret the CPT and PMT results in
unsaturated soil, as there were lack of data and control on the field
boundary conditions. All the uncertainties and limitations involved
with in situ testing such as heterogeneity of soil, unknown stress history,
and stress state of soil further complicate the analysis involve. In
the past, calibration chambers has been used to aid in the process of
developing the correlation of many in situ testing devices results on
saturated soil with different soil parameters. Therefore, calibration
chamber is one alternative to overcome all the uncertainties and limitation
involves with the test results from in situ testing. Calibration chamber
can be used for calibrating CPT and PMT under controlled environment,
where data collected can be used to develop the empirical correlation.
Miller and Muraleethatan (1998) has conducted preliminary pressuremeter
testing in unsaturated soil bed compacted in a rigid wall calibration
chamber and the results obtained seem to be promising
This material is based upon work
supported by the National Science
Foundation under Grant No. 9813137
Any opinions, findings, and conclusions
or recommendations expressed in this
material are those of the author(s) and do not necessarily reflect the
views
of the National Science Foundation.