Understanding soil consolidation testing

Soil
consolidation testing is conducted to predict the safe load-bearing capacity of
any soil type prior to building. For instance, even before construction begins
on large buildings, the foundation soil is tested for compaction. Based on the
results of these tests, developers can proceed confidently with heavier and
taller buildings.

To
test soil for unsuitable compaction, several samples are tested in a soil analysis
laboratory. The testing process simulates the conditions of load and water pore
pressure in the soil and then measures the amount of soil compacted, or compressed
under the load.

A
static load is applied to a piston that transmits the force to the soil sample contained
within the test cell. Water is introduced and maintained at the pressure
expected for the construction site. This pressure is sensed and controlled by a
pressure transducer. The force of the load is sensed by a series of strain
gauge load cells and the movement of the sample during compaction is measured
by an LVDT.

A
compaction test may take a few hours or several days, depending on the soil
conditions and applied load. The primary objective of the test is to verify
that the soil will be strong enough to bear the weight of the building to be
built on that particular site.

In a
commercial soil compaction testing system, a servo-controller is used to apply
a continuous load to the sample instead of heavy weights. The load cell just
beneath the top platen measures the actual force applied and a spring-loaded
LVDT measures the change in thickness of the soil sample as it consolidates.

Validyne
pressure transducers available from Bestech Australia are used to measure pore
pressure while USB2250 signal conditioning can be used as the data acquisition
interface to record pressure, the force sensed by the load cell and the sample
displacement from the LVDT signals.

The
USB2250 can accept all three sensor types directly, including other sensors
such as themocouples and DC voltages. The variety of sensor types used in soil
compaction testing including load cells, LVDTs and pressure transducers make
the USB2250 an ideal sensor interface.

Bestech
will work with customers to integrate the USB2250 into existing soil test
software.

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