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Stabilising the Leaning Tower of Pisa: the Evolution of Geotechnical Solutions
... Tiene siete niveles más una cámara de campanas localizada en la cúspide. Su altura aproximadamente es de 58.6 m, desde el nivel de la cimentación, o 55 m desde Figura 1: Localización de la Torre Campanario de la Catedral de Pisa Fuente: Elaboración propia (2022) Figura 2: Sección de la torre Fuente: Fuente: Elaboración propia (2017) con base en Burland (2008) el nivel del suelo (Jamiolkowski y Viggiani, 2007), con un diámetro de 19.6 m en planta (Burland, 2014). Es de forma cilíndrica y hueca en el centro, soportada por 15 semicolumnas adosadas al muro en primera planta, con un diseño poco común para la época (Ronzani y Ascani, 2011;Ascani, 2014). ...
... Fue ejecutada por Bonanno Pisano, quien construyó los primeros cuatro niveles. En 1178 llegó la primera suspensión -por razones desconocidas- (Burland, 2008). La segunda etapa inició en 1271 y duró seis años bajo la dirección del arquitecto Giovanni Di Simone, que construyó tres niveles más, para alcanzar una altura de siete niveles, pero en 1278 llegó la segunda suspensión a causa de una guerra perdida contra Génova -la Batalla de Meloria-(Bajaj y Choudhary, 2014, p. 81; Jamiolkowski y Viggiani, 2007). ...
... Por tratarse de sucesos pasados, para conocer los detalles se realizó una revisión documental en la que se prestó especial atención a los artículos y reportes técnicos publicados por los principales actores que participaron en las etapas de intervención de la torre: Burland (2008Burland ( , 2014, Croci (2001Croci ( , 2012, Jamiolkowski y Viggiani (2007), Burland et al. (2003), Lodigiani y Macchi (2005) y Jamiolkowski et al. (1993). Asimismo, se puso especial atención en los registros elaborados por cronistas, historiadores y periodistas locales, en donde se destaca la obra de Caldelli y Meucci (2005/2010. ...
Existen numerosas soluciones técnicas para la intervención de edificios patrimoniales que sirven para evitar o reducir la degradación. Aunque estas cuenten con experiencias satisfactorias, no son garantía para tipificarlas. Para explicar este curioso hecho, se recurrió al estudio de las intervenciones realizadas en el transcurso de la historia en la Torre Campanario de la Catedral de Pisa. Este emblemático edificio ha experimentado asentamientos diferenciales desde su construcción, generando su inclinación por lo que es internacionalmente conocida. Durante el transcurso de su existencia ha sido escenario de diferentes tipos de intervenciones, en su mayoría integraciones y liberaciones. Se presenta una revisión sistemática sobre las diferentes y más representativas acciones de intervención, para conocer cómo estas han influido en la variación de su estado de degradación. No todas las acciones implementadas tuvieron éxito. La experimentación en sitio controlada, con modelos a escala, hasta el momento es la vía segura en las intervenciones.
... Engineering can provide is the stabilization of the leaning Tower of Pisa. The efforts of the involved geotechnical engineering committees were intensively reported by Professors Burland andJamiolkowski collaborated with other prestigious geotechnical professionals,(e.g., Jamiolkowski et al., 1993;Burland, et al., 1998;Jamiolkowski, 1999;Jamiolkowski, 2001;Burland, 2008;and Burland et al., 2009) to documentthe geotechnical investigations, the geotechnical instrumentation, the numerical backanalyses of the performance and behavior of the tower considering the soil nature and the events associated with increased ratesof tilt, all with due consideration to time.After determining the mechanism responsible for the movement, a number of solutions were considered,from which the most practical and convenient remedy was implemented. ...
There are numerous evidences that the Ancient Egyptians were pioneers in Geology and Geotechnical Engineering. Some examples of their revolutionary works are presented in this paper to show their genius in mining, quarrying, tunneling, choice of the locations of their structures, and introducing innovative solutions for dealing with problematic soils. Engineers, especially geotechnical engineers, may consider returning to the roots of civilizations and reevaluating the achievements of the ancients by modern means such as Forensic Engineering. This could open the door tounderstanding how the ancients built their wonders and why these wonders survived millenniums. The study of old civilizations could introduce new engineering and construction concepts that benefit the profession today. This paper, which focuses primarily on the Ancient Egyptian engineering achievements, raises questions rather than answers as to what geotechnical engineers actually know about, and from, this great civilization; the authors believe that we know very little despite it being the subject of numerous in-depth studies that date as far back as the fifth century B.C. (the work of Herodotus)and continued till the present day.
The stabilisation of the Tower of Pisa has been a very difficult challenge for geotechnical engineering. The Tower is founded on weak, highly compressible soils and its inclination has been increasing inexorably over the years to the point at which it was about to reach leaning instability. Any disturbance to the ground beneath the south side of the foundation is very dangerous ; therefore the use of conventional geotechnical processes at the south side, such as underpinning, grouting etd., involved unacceptable risk. The internationally accepted conventions for the conservation and preservation of valuable historic buildings, of which the Pisa Tower is one of the best known and most treasured, require that their essential character should be preserved, with their history, craftsmanship and enigmas. Thus any intrusive intervention on the Tower had to be kept to an absolute minimum and permanent stabilisation schemes involving propping or visible support were unacceptable and in any case could have triggered the collapse of the fragile masonry.
In 1990 the Italian Government appointed an International Committee for the safeguard and stabilisation of the Tower. It was conceived as a multidisciplinary body, whose members were experts in arts, restoration and materials, structural engineers and geotechnical engineers. After a careful consideration of a number of possible approaches, the Committee adopted a controlled removal of small volumes of soil from beneath the north side of the Tower foundation (underexcavation). This technique provided an ultra soft method of increasing the stability of the Tower, which is completely consistent with the requirement of architectural conservation.
The paper reports the analyses and experimental investigations carried out to explore the applicability of the procedure for the stabilisation of the Leaning Tower of Pisa. All the results having been satisfactory, the actual underexcavation of the monument was carried out in the years 1999-2001 ; the results obtained are presented and discussed.
Virtually all geotechnical problems involve the flow of fluids, chemicals and energy. A current review of the types of direct and coupled flow through soil is given and assessment of their significance in geotechnical practice is made. Darcy's, Fourier's, Ohm's and Fick's laws provide a suitable practical basis for the analysis of water, heat, electrical and chemcial flows due to gradients of the same type. Prolonged application of gradients of the different types can cause significant changes in the state and properties of a soil, and flows through it. The quantification of coupled flows is most easily done by direct measurement of coupling coefficients when only two types of flow are important. The application of irreversible thermodynamics is useful for quantification of flows in more complex systems. Relationships are provided for the expression of coupling coefficients in terms of directly measureable soil parameters such as hydraulic conductivity. -from Author
Underexcavation has been used in Mexico City to reduce differential settlements in buildings. This paper describes a case history in which the method was applied successfully: the Metropolitan Cathedral and the adjoining Sagrario Church, which settled differentially because of self-weight consolidation and regional subsidence. Underexcavation, which took place between August 1993 and June 1998, was adapted to the particular conditions in the site, and the procedure was followed using extensive instrumentation in order to apply the observational method to control it. Maximum corrective settlements attained with underexcavation were more than 90 cm. Stepwise, the procedure is shown to be an advantageous technique for reducing differential settlements and tilts when obtrusion of the structure cannot be tolerated.
Synopsis
Having stated that consolidation is the main phenomenon in the Tower's underground, two causes are pointed out for the Tower's inclination: the difference in soil consistency on the sides of an east-west axial plane, and the inequality of the contact pressures as a consequence of the induced eccentricity of the load. In the Paper the historyof the second factor through the centuries is reconstructed. The increasing pressures on the southern side have increased the strength and reduced the compressibility, leading toan inversion of the primitive differences: therefore, to avoid danger, a partial redressing of the Tower would be better than the strengthening of the soil. Shifting of the inclination to 90/ (from the present 10%) will very likely be sufficient to bring all soil pressures below the equilibrium values corresponding to the present densities and to achievestabilisation. The straightening could be obtained by boring soil under the Tower on the northern side; and that would be possible according to various schemes, one of which is given below.
Après avoir établi que le phénombne principal qui s'est verifie dans le sol sousjacent la Tour est la consolidation, on distingue deux ordres de causes de I'inclinaison de la Tour: un originaire, 1'eterogénéite du sol des deux cotés d'un plan axial est-ouest, l‘autre dérivé l'excentricité de la résultante des pressions sur la base. L'histoire de ces pressions est reconstruite et on en tire la conséquence que l'eéterogénéité existante à l'époque de la construction est actuellement renversée, c'est à dire que maintenant au coté bas le sol, a une compressibilité beaucoup moindre et une résistance beaucoup plus grande que celles de l'autre coté. Par conséquence pour éliminer tout danger, plutôt qu'améliorer le sol, on devrait reduire les differences de pression en redressant partiellement la Tour; en portant l'inclinaison de lO%, (telle qu'elle est actuellement) a 9% par exemple, on conduirait très probablement toutes les pressions audessous des valeurs d'équilibre correspondantes aux densit´s actuelles et l'on obtiendrait ainsi lastabilisation dCfinitive de la Tour. Le redressement pourrait être obtenu par enléevement de matériau au coté haut; une des modalités possibles pour l'enlèvement est indiquée.
No tower in the world is more famous than the Leaning Tower of Pisa, the most beautiful campanile in Italy. It stands on the Piazzo dei Miracoli - the place of wonders - together with the Duomo and the Baptisterio with their beautiful cupolas and pillared facades. Construction on the Tower began in 1173. It was interrupted in 1178, after three-and-a-half stories were built, because some inclination was observed. Building resumed on the already tilting structure from 1272 to 1278, giving the tower its so-called "banana" shape. As the seventh floor was reached, construction was again interrupted. The bell chamber was finally finished in 1350. Over centuries the Tower progressively inclined. Its safety was studied again and again by various commissions. Then-Prime Minister Andreotti created a new committee transcending the existing Ministry of Monuments. The new group, Comitato di Consulenza per la Salvaguardia della Torre di Pisa, was charged with finding ways to achieve a final stabilization of the Tower.
Some Historic Examples of Underexcavation
- G Johnston
- J B Burland
Sanierungsvorschlag fur den Schiefen Turm von Pisa
- C Veder
The Use of Underexcavation as a Means of Stabilising the Leaning Tower of Pisa: Scale Model Tests', MSc thesis
- H Edmunds