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Geotechnical Characterization, Stability Analysis, and the Stabilization Process for a
Landslide in a area of Barreiras Formation and Granite Residual Soils, Pernambuco
Caractérisation géotechnique, analyse de la stabilité et procédés de stabilisation
pour un glissement de terrain dans des matériaux du type « Barreiras Formation »
et sols de granite résiduel, Pernambuco
Coutinho R.Q.
Federal University of Pernambuco, Brazil
Silva da M.M.
Federal Educational Institute of Pernambuco, Brazil
ABSTRACT: A large number of Brazilians live in conditions that involve elevated risk for landslides. Both technical and social
problems are involved. This study presents results of a research project involving technical support for the Municipal administration
of the City of Camaragibe - PE. An important landslide occurred in an occupied area after a period of intense rainfall, causing
considerable losses for the local population. Three years later, another period of intense rainfall exacerbated the problem, causing
cracks to develop in the walls and foundations of many houses, and broadening the area initially affected. An important program
involving investigation that included field and laboratory activities, instrumentation, and stability and flow analysis was carried out.
The results produced were considered to be very satisfactory, and they were able to point out the main causal factors, along with the
mechanisms involving the landslide, which could then be better understood, and thoroughly studied. Afterwards, a proposal for
stabilization for the entire area was elaborated, aiming to significantly reduce the risk levels by means of superficial and sub-
superficial drainage, geometric modifications, placement of structures for stabilization of the land, and other activities.
RÉSUMÉ : Un grand nombre de brésiliens vivent dans des zones à risque d’un point de vue des glissements de terrain. Cela engendre
des problèmes aussi bien techniques que sociétaux. Les travaux présentés dans cet article découlent d’un projet de recherche financé
par l’administration municipale de la ville de Camaragibe – PE. Suite à un épisode pluvieux très important, un glissement de terrain
s’est produit et a causé des dégâts considérables pour la population locale. Trois années plus tard, un nouvel épisode pluvieux a
aggravé la situation et de nombreux ouvrages furent endommagés (murs de soutènement, fondations de maisons, …). Un programme
d’investigation important fût alors mis en place : instrumentation sur site, analyses de stabilité et d’écoulement. On présente dans cet
article une synthèse des résultats obtenus ainsi que les mécanismes aux origines des instabilités. Pour finir, une solution de
stabilisation du site est proposé, avec pour but de réduire significativement le niveau de risque (drainage, modification géométrique de
la pente et mise en œuvre d’ouvrages de stabilisation).
KEYWORDS: geotechnical characterization, slope stability, stabilization process.
1 INTRODUCTION
This paper presents study results from a research project,
including details involving technical support supplied to the
Municipal administration of the City of Camaragibe – PE,
Brazil. The area investigated is located in the Township of
Camaragibe, belonging to the western portion of the Recife
Metropolitan Region. The landslide that occurred was classified
as a multiple rotational landslide, characterized by the
appearance of various steps along its slope. Geological
characteristics of the area studied define an unsaturated granite
residual soil that is partially covered by the Barreiras Formation.
The residual soil of granite is found throughout the entire city.
In some places, the granite rock mass is exposed.
In the Recife Metropolitan Region, it is common to find
crystalline based rocks (Granite-Gneissic complex) covered by
granite residual soils that originate from a crystalline structure;
and by sediments from the Barreiras Formation. The crystalline
base is formed by ancient intrusive rocks (1.5 to 21 billion
years) belonging to the Pernambuco – Alagoas Massif. It
presents at least four phases of deformation, the latter of which,
associated to the faults deformed, resulted in the formation of
the “Pernambuco Lineamento”.
The results presented here refer to a synthesis of the
program of geotechnical characterization (field and laboratory
testing, along with instrumentation), flow and stability analysis,
and proposals for stabilization of the area in an attempt to
significantly reduce the level of risk. This study aims to give
continuity to a research project by the GEGEP – DEC / UFPE,
with support from the CNPq/FACEPE, designed to comprehend
and elaborate mechanisms involving instability of slopes, and
providing manners in which stabilization can be achieved.
2 GEOTECHNICAL CHARACTERIZATION
In the studies, an extensive effort involving
in situ
and
laboratory investigation was carried out. For basic geotechnical
characterization, laboratory analysis consisted of physical,
chemical, and mineralogical characterization tests, strength tests
(including direct shear tests, and direct shear tests utilizing
controlled suction), and oedometric tests.
The
in situ
investigation carried out in the area was
performed by using topographic profiles of the region, cross
sections, geological engineering mapping, subsurface
exploration (soil / rock mass – SPT / RQD measurements), soil
moisture content profiles, sampling of soils (Block and
Denison), and field permeability tests (Guelf). Field
instrumentation utilized piezometer, water table level,
inclinometer, and rainfall measurement equipment. More
information can be found in Silva (2007) and Silva
et al.
(2009).
2.1 Field Investigation Results
For the subsurface exploration, twelve boreholes were utilized
in the area investigated. Ten were carried out in soil (SPT), and
