Environmental Engineering Reference
In-Depth Information
Geotechnical description of halloysite clays from la Palma
island (spain)
J. estaire, M. santana & J.a. Díez
Laboratorio de Geotecnia (CEDEX, Mº de Fomento), Madrid, Spain
aBsTRacT: in this paper the geotechnical description of a halloysite clay, coming from boreholes
performed in Barlovento Dam, is made. it is important to remark this material had a difficult behaviour
during the performance of laboratory tests, clearly different of the materials soil Mechanics usually treats
with. The geotechnical description comprised the following aspects: a) identification tests: the grain size
and plasticity tests had to be made with different procedures of the ones described in the technical span-
ish standards due to the special characteristic of the material; b) X-Ray diffraction tests; c) chemical
tests; d) dry density and natural water content of the material; e) strength tests that comprised dynamic
penetration tests (sPT and DPsh test),triaxial and direct shear tests and pressuremeter tests made in the
boreholes; f) deformability tests that included oedometer and pressuremeter tests g) permeability and
dispersibility tests.
1
inTRoDUcTion
island archipelago. The dam was built in 1970
and it has a 3,2 hm
3
maximum capacity and a
300.000 m
2
area. it was built inside a volcanic
cone of elliptical section with 400 and 500 m
long axis. in the bottom and in the walls of the
caldera, a PVc layer was placed to waterproof
the reservoir.
Figure 1 shows a photograph of the reservoir
once it was emptied.
in one of the periodical maintenance operations,
some cracks in the waterproof layer and great set-
tlements in the bottom of the reservoir were dis-
covered. Figure 2 shows the location of the cracks
in the PVc layer and the extension of the zones
with same settlements.
The analysis of the previous figure makes it
possible to state the following facts:
a. settlements only affect the bottom of the reser-
voir and they reflect the elliptical shape of the
bottom.
in the bottom of Barlovento Dam, situated in the
north of la Palma island, settlements about 2 m
were detected. With the aim of determining the
causes of such movements (estaire et al., 2008)
a geotechnical investigation campaign was per-
formed. in such study, it was discovered that the
ground was mainly formed by halloysite clays.
it is important to remark the laboratory tests
made with the halloysite clay material were dif-
ficult to perform, due to its clearly different
geotechnical behaviour compared with the soils
usually studied by soil Mechanics. (hurlimann
et al., 2001).
2
PRoBleMs DeTecTeD in The DaM
laguna de Barlovento Dam is situated in
the northeast of la Palma island, in canary
Figure 1.
aerial photograph of the dam, once it was emptied.
