Effects of subsurface cavity expansion in clays

Subsurface cavity expansion in clay induced by compaction grouting can generate upward displacement of clay and/or increase in effective stress leading to consolidation, resulting in settlement compensation and/or shear strength enhancement respectively. However, the two potential benefits of subsurface cavity expansion may offset each other. Experiments and numerical simulations on the engineering behaviour of E-grade kaolin induced by subsurface pressure-controlled cavity expansion were conducted to investigate the interrelationship between compensation effectiveness and shear strength enhancement. The results of numerical simulations are in reasonably good agreement with the experimental data, indicating that the numerical simulation procedure adopted is a plausible and reliable technique to describe the engineering behaviour of clays induced by pressure-controlled cavity expansion. Effects of cavity expansion rate, cavity expansion volume, injection point spacing, and stress history on compensation effectiveness and shear strength enhancement were studied. Practical applications of the results are also proposed.published_or_final_versio

Multi-messenger observations of a binary neutron star merger

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ~1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+8-8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Mo. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ~40 Mpc) less than 11 hours after the merger by the One- Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ~10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ~9 and ~16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta

A new laboratory apparatus for grout injection studies

The design, fabrication, and assembly of a new laboratory apparatus for the investigation of fundamental behavior of compaction grouting and fracture grouting are presented in this paper. Clayey soil specimens of different overconsolidation ratios can be prepared to study the grout deformation pattern, fracture pattern, and consolidation behavior of soil induced by grout injection as a function of operating parameters. Ideal compacting grouting is replicated by expanding a latex balloon placed within the soil specimen and fracture grouting by injecting epoxy resin or high water content cement bentonite grout into the soil specimen. Moreover, the apparatus can accommodate multiple-point grout injection experiments to examine the behavior of grout interactions. Illustrative results are also presented in the paper. Copyright © 2006 by ASTM International.link_to_subscribed_fulltex

Effects of subsurface cavity expansion in clays

Subsurface cavity expansion in clay induced by compaction grouting can generate upward displacement of clay and/or increase in effective stress leading to consolidation, resulting in settlement compensation and/or shear strength enhancement respectively. However, the two potential benefits of subsurface cavity expansion may offset each other. Experiments and numerical simulations on the engineering behaviour of E-grade kaolin induced by subsurface pressure-controlled cavity expansion were conducted to investigate the interrelationship between compensation effectiveness and shear strength enhancement. The results of numerical simulations are in reasonably good agreement with the experimental data, indicating that the numerical simulation procedure adopted is a plausible and reliable technique to describe the engineering behaviour of clays induced by pressure-controlled cavity expansion. Effects of cavity expansion rate, cavity expansion volume, injection point spacing, and stress history on compensation effectiveness and shear strength enhancement were studied. Practical applications of the results are also proposed.published_or_final_versio

Laboratory study of feasibility of compaction grouting of soil

Compaction grouting has been utilized for various ground improvement applications in geotechnical engineering. However, there is no standard laboratory method or experimental procedure to determine the feasibility of compaction grouting of soil. Therefore, decision on the adoption of the technology and choices of operation parameters are based on past experience and empirical rules of thumb. A new laboratory apparatus and new experimental procedures were developed to establish the feasibility of compaction grouting of soil. The concept is analogous to the Proctor test for compaction. The relationship between the input grouting energy and the resulting compaction as a function of initial water content and relative compaction of the soil is quantified experimentally. The quantification can provide the necessary data for the geotechnical engineer to evaluate the viability and applicability of compaction grouting for their specific project needs. The design, fabrication, and assembly of the new apparatus are presented with results to demonstrate the workability of the apparatus. © 2011 Taylor & Francis.link_to_subscribed_fulltex