1571
Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
Pioneer application of a dynamic penetrometer and boroscope in archeological
prospecting
Application pionnière d’un pénétromètre dynamique et d’un boroscope dans la prospection
archéologique
J.L. Rangel-Núñez
Universidad Autónoma Metropolitana plantel Azcapotzalco
L. Barba
Instituto de Investigaciones Antropológicas, UNAM
E. Ovando, G. Auvinet & E. Ibarra-Razo
Instituto de Ingeniería, UNAM
ABSTRACT: This paper presents a pioneer application of a geotechnical technique in archaeological prospecting. A light dynamic
penetrometer, georadar and geo-boroscope were applied to determine the superficial stratigraphic profile at the Cacaxtla Gran
Basamento archeological zone, in Mexico, in areas where walls and floors present important cracks. From the geotechnical point of
view, the Gran Basamento is an artificial platform conformed by heterogeneous fills (mainly tuff rock fragments, silty and sandy
soils) where pre-hispanic structures were built (from 450 bC to 900 aC). There is an important lack of knowledge about the
mechanical characteristics and position of the soil deposits or buried archeological structures. The interpretation of the results shows
that it is not only possible to obtain a very good idea of the characteristics and distribution of the superficial soil deposits, and to
evaluate the origin of cracks and their mechanisms to avoid slope and wall instabilities, but that it is also possible to identify stages of
construction of the pyramid for the hypothetical reconstruction of the layers and structures that conform this archeological monument.
Based on the geotechnical information, pre-hispanic floors at different construction stages were correlated with high dynamic cone
resistance and very loose granular material with low dynamic cone resistance, which was a risk condition in slope stabilization. Both
conditions were verified visually with a geo-boroscope.
RÉSUMÉ: Cet article présente une application de pionnier d'une technique de prospection archéologique en géotechnique. Un
pénétromètre dynamique, le géo radar et géo-endoscope ont été appliquées pour déterminer le profil superficiel stratigraphique du
Gran Basamento à Cacaxtla, au Mexique, dans les zones où les murs et les planchers présentent des fissures importantes. Du point de
vue géotechnique, l'Gran Basamento est une plate-forme artificielle conformé par hétérogène comble (surtout des fragments de roche
de tuf, limoneux et les sols sableux) où préhispaniques structures ont été construites (à partir de 450 avant JC à 900 AC). Il ya un
manque important de connaissances sur les caractéristiques mécaniques et la position des dépôts de sol ou enterrées structures
archéologiques. L'interprétation des résultats montre qu'il est non seulement possible d'obtenir une très bonne idée des caractéristiques
et de la répartition des dépôts superficiels du sol, et d'évaluer l'origine des fissures et leurs mécanismes pour éviter les instabilités de
pente et le mur, mais qu'il est également possible d'identifier les étapes de la construction de la pyramide pour la reconstruction
hypothétique des couches et des structures conformes de ce monument archéologique. Sur la base des informations géotechniques,
préhispaniques étages à différentes étapes de la construction ont été corrélés avec résistance au cône dynamique élevée et très lâche
matériau granulaire avec résistance au cône dynamique faible, ce qui était une condition de risque dans la stabilisation des talus.
KEYWORDS: archeology, geo-boroscope, dynamic penetrometer, georadar, geophysical prospecting.
1 INTRODUCTION
The
Gran Basamento
of the Cacaxtla archeological zone is,
from the geotechnical point of view, an artificial platform of the
natural terrain carried out with heterogeneous fills formed with
fragments of tuff and soil, on which different types of structures
were placed, from various pre-hispanic periods (450 b.C. to 900
a.C.) and using varied construction techniques, such as
excavations or the construction of walls or columns made of
adobe (Fig 1).
Figure 1. Cacaxtla
’s Acropolis
(National geographic, 1992)
Currently, the geometrical and mechanical characteristics of
the fills that form the Gran Basamento are unknown, as well as
position and composition of support material. Given the
different construction stages, the use of each building that
integrates this structure and the presence of walls and columns,
the definition of the stratigraphic units is complex. On the other
hand, the Gran Basamento has been and will continue to be
subjected to the effects of environmental processes and human
activity, which induce changes in its constitution, which in turn
generate movements and a rearranging of the material that
constitutes the platform and the structures that integrate it. The
movements and rearrangements generated are shown through
the superficial cracks of the structure, present on walls, floors
and columns, but mainly on some of the valuable polychrome
murals. Therefore, it is necessary to know their origin, describe
their current condition and follow up their evolution to assess
the stability and integrity of the platform in the short, medium
and long terms.
To date, the cracking on some of the platform
’s zones is at
an advanced stage of development, but in others it remains
incipient. In effect, there are cases where the cracking has
provoked instabilities on walls, floors and cuts (fall of blocks,
chipping, spalling, etc.), that could have contained or not
Pioneer application of a dynamic penetrometer and boroscope in archeological
prospecting
Application pionnière d’un pénétromètre dynamique et d’un boroscope dans la prospection
archéologique
Rangel-Núñez J.L.
Universidad Autónoma Metropolitana plantel Azcapotzalco
Barba L.
Instituto de Investigaciones Antropológicas, UNAM
Ovando E., Auvinet G., Ibarra-Razo E.
Instituto de Ingeniería, UNAM
