Clay Behavior, Ground Response and Soil-Structure Interaction Studies in Mexico City

This paper focuses on the most relevant results of recent investigations carried out on the behavior of Mexico City clays under dynamic loading, on the effects of soil site conditions and on the evaluation of the dynamic soil-structure interaction phenomenon. The paper shows the impact of these studies upon foundation engineering practice in earthquake-prone regions where clayey deposits exist, and advances simple, yet accurate, procedures to develop site-dependent, building-specific input motions for the design of structures in the Valley of Mexico. It discusses recent seismic observations that clarify the origin of the long coda observed in several records obtained in the lake zone in Mexico City

Settlements Induced by Soft Ground Tunneling

Ground settlements induced by air-pressure shield tunneling throughout the soft clays of Mexico City have been monitored in five test sections by means of settlement points installed at various depths and distances from the tunnel axis. Subsoil conditions and soil characteristics at each site were thoroughly studied in the field and in the laboratory. Measured settlement profiles have been compared to those computed by a simplified analytical procedure showing very good agreement

Identity Behind Glass: The Second Gore Place Greenhouse

This thesis examines the second greenhouse at Gore Place, a historic country estate in Waltham, Massachusetts. Gore Place was owned by and named for Christopher and Rebecca Gore, members of the 18th- and 19th-century political and economic elite in New England. The greenhouse was constructed in 1806, and excavation at the site took place in 2004, 2008, and 2012. The latter two projects were data recovery excavations, which exposed portions of the greenhouse’s foundations and interior, as well as several features in the yard surrounding the building. Historic greenhouses were prestigious structures, financially accessible only to institutions, governments, and the wealthy elite. How a greenhouse was built and organized and what plants it contained can yield information on the motivations behind its construction. To that end, this thesis analyzed the history of the Gores and their country estate, the culture of the 18th- and 19th-century New England elite, the methods and reasons for greenhouse construction, and the archaeological results from the 2004-2011 excavations. This analysis indicates that the Gores built their greenhouse in the efficient “Lean-to” style, which is characterized by a sloped front wall made almost entirely of glass. The building was heated via a furnace and flue system, and grew grapes in beds and other potted plants on shelves or platforms. The greenhouse yard was explicitly arranged to support the building. The Gores were motivated to build the 1806 greenhouse as part of an expression of Christopher’s aristocratic identity and the pair’s commitment to scientific agriculture and horticulture

Transient tunneling effects of resonance doublets in triple barrier systems

Transient tunneling effects in triple barrier systems are investigated by considering a time-dependent solution to the Schr\"{o}dinger equation with a cutoff wave initial condition. We derive a two-level formula for incidence energies $E$ near the first resonance doublet of the system. Based on that expression we find that the probability density along the internal region of the potential, is governed by three oscillation frequencies: one of them refers to the well known Bohr frequency, given in terms of the first and second resonance energies of the doublet, and the two others, represent a coupling with the incidence energy $E$. This allows to manipulate the above frequencies to control the tunneling transient behavior of the probability density in the short-time regim

Three Recent Damaging Earthquakes in Mexico

Seismicity in Mexico is largely influenced by subduction earthquakes that originate along much of its Pacific Coast. These events have recurrently damaged Mexico City but other less frequent earthquakes produced by other sources and mechanisms also contribute to seismic hazard there and have damaged other important cities and towns. In this paper we review, from the point of view of geotechnical engineering, the effects of three of these less frequent events: the Manzanillo earthquake of Octobrer 9, 1995, the Tehuacán Earthquake of June 6, 1999 and the Tecomán Earthquake of January 21, 2003

A-branes, foliations and localization

This paper studies a notion of enumerative invariants for stable $A$-branes,and discusses its relation to invariants defined by spectral and exponentialnetworks. A natural definition of stable $A$-branes and their counts isprovided by the string theoretic origin of the topological $A$-model. This isthe Witten index of the supersymmetric quantum mechanics of a single $D3$ branesupported on a special Lagrangian in a Calabi-Yau threefold. Geometrically,this is closely related to the Euler characteristic of the $A$-brane modulispace. Using the natural torus action on this moduli space, we reduce thecomputation of its Euler characteristic to a count of fixed points viaequivariant localization. Studying the $A$-branes that correspond to fixedpoints, we make contact with definitions of spectral and exponential networks.We find agreement between the counts defined via the Witten index, and the BPSinvariants defined by networks. By extension, our definition also matches withDonaldson-Thomas invariants of $B$-branes related by homological mirrorsymmetry.<br

Liquefaction of the Enmedio Island Soil Deposits

The results of field testing and of simplified liquefaction analyses of the Enmedio Island soil deposits are presented and discussed in this paper. It is found that for this case history simple criteria for assessing liquefaction potential yield results in accord with field behavior

An Experimental Study to Assess the Shear Modulus Degradation by Fatigue of Mexico City Clay

In this research, the degradation by fatigue of Mexico City clay is studied using a triaxial equipment where the cyclic stress amplitude was maintained constant during the experiment. The variables considered in the study were the following: state of the soil, effective mean confining stress, magnitude of cyclic stress and number of loading cycles. Undisturbed samples, anisotropically and isotropically consolidated, were subjected to cyclic loading for this purpose. When analyzing the cyclic stress-strain response with the number of cycles a threshold of permanent deformation in function of the cyclic deviator stress and axial strain was found. When the cyclic strain exceeds this distinctive value the rate of permanent (plastic) deformations accumulate faster. For practical applications of computing permanent deformations in Mexico City a simplified method is proposed. This method considers the above threshold and a hyperbolic model to represent the cyclic response in Mexico City clays