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Accessing GeoenvironmentaI Data: From On-line to Expert Systems
4.1.2 General coherence verification
This part concerns the verification of the general coherence between different tests
performed at the site by means of established correlations.
4.2
Site independent verification
The second level of data quality assessment concerns site independent comparison
between parameters from tests performed at a given site and typical parameters
obtained from the same type of tests performed on a similar type of soil at other
sites available in the database.
5 ApPLICATION TO THE MENARD PRESSUREMETER
There is a large array of in-situ tests currently in use in geotechnical investigations.
Some of the tests are performed by pushing a test device directly into the ground
while others require the drilling of a borehole before introducing the testing
device. The selected test for use in the prototype expert system is the Menard
pressuremeter test and it belongs to the latter group. The pressure meter test is
performed by expanding a cylindrical cell into a soil mass by increasing the
internal pressure and measuring the corresponding volume change. The quality of
a pressuremeter test is highly dependent on the quality of the boring and the
quality of the test procedure.
The result of the test is a curve of pressure versus volume from which we can
calculate three mechanical parameters: a pressuremeter deformation modulus E, a
creep pressure Pf, and a limit pressure PI.
These three parameters are related by statistically established correlations for
different classes of soils depending on the soil nature, its consolidation state and its
consistency. The ratio EIPI for a normally consolidated clay, for example, is within
the range of 8-15. The PI for the same soil is within 0.5-3 MPa if the clay is soft,
3-8 MPa if the clay is plastic and 8-40 MPa if we have a stiff clay. The ratio Pl/Pf
is about 1.7 for clay and between 1.7 and 2 for sand.
This knowledge allows us to check pressuremeter results and to detect any
deviation. A one site verification can be made by using knowledge about the
factors which could affect the quality of the pressuremeter test results:
• The boring operation is very important for the quality of the
pressuremeter test and must be checked. The French standard NF P-94
110, has divided boring methods for pressuremeter use into four classes:
recommended, tolerated, prohibited and misfit. We must take into
account the class of the method used, but the effect of one tolerated
method may vary from one soil type to another. Knowledge gathering
on the subject is necessary.
• The choice of the type of pressuremeter is important for the precision
of the data.
Accessing GeoenvironmentaI Data: From On-line to Expert Systems
4.1.2 General coherence verification
This part concerns the verification of the general coherence between different tests
performed at the site by means of established correlations.
4.2
Site independent verification
The second level of data quality assessment concerns site independent comparison
between parameters from tests performed at a given site and typical parameters
obtained from the same type of tests performed on a similar type of soil at other
sites available in the database.
5 ApPLICATION TO THE MENARD PRESSUREMETER
There is a large array of in-situ tests currently in use in geotechnical investigations.
Some of the tests are performed by pushing a test device directly into the ground
while others require the drilling of a borehole before introducing the testing
device. The selected test for use in the prototype expert system is the Menard
pressuremeter test and it belongs to the latter group. The pressure meter test is
performed by expanding a cylindrical cell into a soil mass by increasing the
internal pressure and measuring the corresponding volume change. The quality of
a pressuremeter test is highly dependent on the quality of the boring and the
quality of the test procedure.
The result of the test is a curve of pressure versus volume from which we can
calculate three mechanical parameters: a pressuremeter deformation modulus E, a
creep pressure Pf, and a limit pressure PI.
These three parameters are related by statistically established correlations for
different classes of soils depending on the soil nature, its consolidation state and its
consistency. The ratio EIPI for a normally consolidated clay, for example, is within
the range of 8-15. The PI for the same soil is within 0.5-3 MPa if the clay is soft,
3-8 MPa if the clay is plastic and 8-40 MPa if we have a stiff clay. The ratio Pl/Pf
is about 1.7 for clay and between 1.7 and 2 for sand.
This knowledge allows us to check pressuremeter results and to detect any
deviation. A one site verification can be made by using knowledge about the
factors which could affect the quality of the pressuremeter test results:
• The boring operation is very important for the quality of the
pressuremeter test and must be checked. The French standard NF P-94
110, has divided boring methods for pressuremeter use into four classes:
recommended, tolerated, prohibited and misfit. We must take into
account the class of the method used, but the effect of one tolerated
method may vary from one soil type to another. Knowledge gathering
on the subject is necessary.
• The choice of the type of pressuremeter is important for the precision
of the data.