Diagnostic and Analysis of Specific Soil with Ground Water Level and Plain Concrete Slab Interaction

in case of a thin concrete slab and increased groundwater level. The
soil and structure interaction is a complex task applied in cases
when necessary to sufficiently consider the proposal's safety and
economy. The particular topic dealt with is the performed specific
experiment of a concrete slab on the subsoil that is subsequently
simulated using 3D computing models. The performed experiment
is a concrete slab with dimensions 2000 x 2000 mm. The concrete
slab thickness was 150 mm. Computing models are based on the
Finite Element Method and non-linear analyses. The specificity of
the experiment is that it simulates extreme foundation conditions
when the groundwater level almost reaches the foundation base.
The experiment confirmed the significant effect of the groundwater
level, the reduction of the overall bearing capacity of the slab and
the rapid disturbance and collapse of the slab. Numerical models
also described very well the occurrence of cracks and slab collapse.
The results were in good agreement with the experimental testing.
Major specificities include that the measuring and load test records
are supplemented with an acoustic emission to identify concrete
cracks. Findings from acoustic emission make it possible to
describe the formation of cracks at a time when cracks are not
visible and to verify the subsequent behaviour of the slab. The
research task presented also includes detail laboratory tests of the
concrete used. Laboratory tests include tests of compressive
strength, modulus of elasticity and tensile strength. Tensile strength
was determined based on splitting tensile strength and bending
tensile strength tests. In the case of bending tensile strength, test
variants were performed, which differed in the test configuration
(three-point bending test, four-point bending test), the size of the
test specimens and the notch in the middle of their span. Numerical
modelling of the slab's interaction with the subsoil is also preceded
by modelling a small structural element, a beam with reinforcement.
Numerical modelling itself is also based on the use of the concept
identification of fracture mechanics parameters by laboratory tests.