A multiscale approach for the consideration of spatial groundwater flow in the stability analysis of a large excavation pit

Papakonstantinou, Spyridon; Pimentel, Erich; Anagnostou, Georg

doi:10.1201/b10551-52

Cited by 2 publications

(3 citation statements)

References 6 publications

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“…The original seawater concrete mix design of the harbor concretes has been previously described as vol%, using empirical observations and the recommendation of a 1:2 volumetric ratio of lime:pulvis volcanic ash indicated by Vitruvius (Oleson et al 2004(Oleson et al , 2006Brandon et al 2008). Calculations of the relative proportions of geologic materials as weight percent (Appendix Table 1) use bulk mass densities of 1200 to 1400 kg/m 3 for the lithified facies of the NYT (Papakonstantinou et al 2012), as an approximation or the Bacoli Tuff; 880 kg/m 3 for the dry lump quicklime (Brune 2011), calcined at about 900 °C; and 1000 to 1200 kg/m 3 for the loosely consolidated facies of the NYT (Papakonstantinou et al 2012), a source of lightweight aggregate in modern structural concretes (de'Gennaro et al 2005), which provides an approximation for the pumiceous ash pozzolan, possibly from the Averno 2 pumice fall deposit (Fig. 5).…”

Section: Thermal Model Of the Baianus Sinus Breakwatermentioning

confidence: 99%

Unlocking the secrets of Al-tobermorite in Roman seawater concrete

Jackson¹,

Chae²,

Mulcahy³

et al. 2013

American Mineralogist

146

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Ancient Roman syntheses of Al-tobermorite in a 2000-year-old concrete block submerged in the Bay of Pozzuoli (Baianus Sinus), near Naples, have unique aluminum-rich and silica-poor compositions relative to hydrothermal geological occurrences. In relict lime clasts, the crystals have calcium contents that are similar to ideal tobermorite, 33 to 35 wt%, but the low-silica contents, 39 to 40 wt%, reflect Al 3+ substitution for Si 4+ in Q 2 (1Al), Q 3 (1Al), and Q 3 (2 Al) tetrahedral chain and branching sites. The Al-tobermorite has a double silicate chain structure with long chain lengths in the b [020] crystallographic direction, and wide interlayer spacing, 11.49 Å. Na + and K + partially balance Al 3+ substitution for Si 4+ . Poorly crystalline calcium-aluminum-silicate-hydrate (C-A-S-H) cementitious binder in the dissolved perimeter of relict lime clasts has Ca/(Si+Al) = 0.79, nearly identical to the Al-tobermorite, but nanoscale heterogeneities with aluminum in both tetrahedral and octahedral coordination. The concrete is about 45 vol% glassy zeolitic tuff and 55 vol% hydrated lime-volcanic ash mortar; lime formed <10 wt% of the mix. Trace element studies confirm that the pyroclastic rock comes from Flegrean Fields volcanic district, as described in ancient Roman texts. An adiabatic thermal model of the 10 m 2 by 5.7 m thick Baianus Sinus breakwater from heat evolved through hydration of lime and formation of C-A-S-H suggests maximum temperatures of 85 to 97 °C. Cooling to seawater temperatures occurred in two years. These elevated temperatures and the mineralizing effects of seawater and alkali-and alumina-rich volcanic ash appear to be critical to Al-tobermorite crystallization. The long-term stability of the Al-tobermorite provides a valuable context to improve future syntheses in innovative concretes with advanced properties using volcanic pozzolans.

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Section: Thermal Model Of the Baianus Sinus Breakwatermentioning

confidence: 99%

Unlocking the secrets of Al-tobermorite in Roman seawater concrete

Jackson¹,

Chae²,

Mulcahy³

et al. 2013

American Mineralogist

146

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“…To solve the equation of transient heat conduction, appropriate values must be assigned to the coefficients ρ i , c pi , k i . The values used in this work have been derived from the literature (Papakonstantinou et al [6] and Rocca [3]). The thermal characteristics as mineral density, dry density, porosity, wet density of the soil layers and jet-grouting, and the thermal characteristics dependent on the frozen and unfrozen phase, as thermal conductivity and heat capacity, are reported in Table 1.…”

Section: Of 24mentioning

confidence: 99%

“…The results proposed by the author, applied to Neapolitan tuff, were compared with those obtained from a series of numerical analyses conducted by using the finite element method as a discretization technique, and with experimental data measured on site during freezing operations carried out for the realization of the galleries for the stations of Piazza Dante and Piazza Garibaldi of metro Line 1 in Napoli (Italy). Papakonstantinou et al [6] first analyzed the experimental data of monitored temperatures in the ground during the freezing process, and then performed a numerical analysis through the FREEZE calculation code, a thermohydraulic software developed at the ETH in Zurich. The authors found that the thermal conductivity of the soil is an important parameter to be taken into account, and can be reasonably estimated by a posterior numerical analysis, if it not known a priori.…”

Section: Introductionmentioning

confidence: 99%

Modeling Artificial Ground Freezing for Construction of Two Tunnels of a Metro Station in Napoli (Italy)

Mauro

Normino

Cavuoto³

et al. 2020

Energies

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An artificial ground freezing (AGF) technique in the horizontal direction has been employed in Naples (Italy), in order to ensure the stability and waterproofing of soil during the excavation of two tunnels in a real underground station. The artificial freezing technique consists of letting a coolant fluid, with a temperature lower than the surrounding ground, circulate inside probes positioned along the perimeter of the gallery. In this paper, the authors propose an efficient numerical model to analyze heat transfer during the whole excavation process for which this AGF technique was used. The model takes into account the water phase change process, and has been employed to analyze phenomena occurring in three cross sections of the galleries. The aim of the work is to analyze the thermal behavior of the ground during the freezing phases, to optimize the freezing process, and to evaluate the thickness of frozen wall obtained. The steps to realize the entire excavation of the tunnels, and the evolution of the frozen wall during the working phases, have been considered. In particular, the present model has allowed us to calculate the thickness of the frozen wall equal to 2.1 m after fourteen days of nitrogen feeding.

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A multiscale approach for the consideration of spatial groundwater flow in the stability analysis of a large excavation pit

Cited by 2 publications

References 6 publications

Unlocking the secrets of Al-tobermorite in Roman seawater concrete

Unlocking the secrets of Al-tobermorite in Roman seawater concrete

Modeling Artificial Ground Freezing for Construction of Two Tunnels of a Metro Station in Napoli (Italy)

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