Collapse of Braced Excavation in Singapore

International Symposium on Backwards Problem in Geotechnical Engineering and Monitoring of Geo-Construction, Green Hall, Kensetsu-Koryu-kan, 2011/07/14-15After the collapse of the subway excavation in the Nicoll Highway, extensive in-situ investigations were carried out to identify causes of the accident. The results of detailed studies disclosed that lack of toe-in depth of the diaphragm wall into the stiff competent strata could be one of the causes of the incident. This aspect of the studies is highlighted in this paper

Performances of Rockfill Dams During Recent Large Earthquakes

There has been increasingly high intensity of acceleration ever recorded during earthquakes in recent times. In consistence with this trend several characteristics have been unearthed regarding performances of rockfill dams. With due considerations to these, damage features of high rockfill dams during recent earthqukes in Japan and China are briefly introduced herein, together with those previously reported. As an indicator of overall distress to the dams, the crest settlement was taken up and it was shown that the settlement tends to increase up to about 1.5% of the height of the dam with increasing acceleration during earthquakes

Post-Earthquake Failure of a Tailings Dam Due to Liquefaction of Pond Deposit

At the time of the Izu-Ohshima-Kinkai earthquake of January 15, 1978 in Japan, two darns retaining tailings from Mochikoshi gold mine failed, leading to a release of a large volume of tailings. One of the darns, No.1 dike, collapsed almost simultaneously with the shaking of the main shock, but another darn, No.2 dike, failed about 24 hours later at a time when there was no shaking. The failure of the No.1 dike is known to have been triggered by the liquefaction which developed in the tailings deposit in the impoundment pond. The cause of the failure in the No.2 dike has not, however, been studied and left open to question. To provide a basis to answer this question, an attempt was made to analyze outward movement of phreatic surface within the dike fills which is motivated by an increase in pore water pressure due to liquefaction developing in the pond deposit behind the retaining dike. It was shown that the phreatic surface could move up to a level near the downstream surface by the time the failure of the dike took place. At each stage of the phreatic surface movement slope stability analysis was performed using the conventional method and factors of safety were calculated. Results of the analyses showed that the factor of safety drops approximately to unity at the stage when the phreatic surface reaches a location in proximity to the surface of the slope. The period of time elapsed for the phreatic surface to reach the near-surface location was also computed and shown to be nearly coincident with the time period between when the earthquake occurred and when the failure actually took place in the No.2 dike

Flow Failure of Liquefied Sand in Large-Scale Shaking Tables

Laboratory studies on flow failure in liquefied sand deposits using large-scale shaking tables are briefly introduced, together with a case study on the lateral deformation in the field. The key parameters influencing the occurrence of flow-type deformation are discussed in an effort to figure out a mechanism or scenario of the flow failure. In one series of the laboratory studies, shaking table tests were performed to examine the effectiveness of a preventive measure against the flow slide. This aspect is also discussed briefly

Mass Spectral Fragmentations. I. Mass Spectral Date on the Synthetic Intermediates Related to the Preparation of Linaloyl Oxide

This paper describes mass spectral data from synthetic intermediates of linaloyl oxide. The fragmentation of sulfur functional groups including compounds l-8 would provide fruitful evidences for structural assignment of acyclic and alicyclic monoterpenoid precursors. Since, 1,3-dithianyl group in l,2, and 3 can provide a base peak and the elimination of the sulfinyl group from 7 and 8 is considered to occur at the initial stage of the fragmentation

Cyclic Strength of Undisturbed Mine Tailings

In order to update existing regulations for the seismic design of tailings retention dikes, extensive investigations were undertaken for 15 existing tailings dams throughout Japan. Undisturbed samples procured from the tailings disposal ponds were tested ln the laboratory to determine the cyclic strength of the in-situ tailings deposits. The results of cyclic triaxial tests on these materials are summarized by means of empirical formulae which are recommended for incorporation in the new seismic design code for the tailings dams

Modelling the Deformation of Sand during Cyclic Rotation of Principal Stress Directions

The paper presents an elastoplastic constitutive model for the deformation of sand during cyclic rotation of principal stress directions. The model employs a plastic potential theory that allows for the dependency of flow on the stress increment direction and a stress-dilatancy relation incorporating the effects of noncoaxiality. The continuous plastic deformation of sand during principal stress rotation at constant shear stress level is allowed for in the model by using a small elastic area in the stress space. The effects of cyclic stress history is modelled by using discrete surfaces of equal hardening modulus which are allowed to move with the stress point during loading. Additionally, the plastic hardening modulus is allowed to stiffen during cyclic loading depending on the amount of accumulated plastic normalized work. The model is used to simulate the deformations in the hollow cylindrical specimen subjected to several cycles of principal stress rotations. The model is shown to be capable of satisfactorily predicting the response of sand during cycles of principal stress rotations

Analyzing and simulating supply chain disruptions to the automobile industry based on experiences of the Great East Japan Earthquake

The Great East Japan Earthquake revealed serious weaknesses in the supply chain management (SCM) employed by Japanese industries, and particularly by the automobile industry. Observed supply chain disruptions and production line shutdowns are recognized as symbolic of weaknesses in industrial SCM. The Japanese automobile industry in particular is now keen to improve supply chain resiliency in terms of automobile assembly line continuity. In view of this, we i) review observed negative impacts of the Great East Japan Earthquake on the automobile industry, ii) identify current strategies being evaluated by the automobile industry for improving supply chain resiliency, iii) develop a numerical supply chain model for the automobile industry, and iv) evaluate efforts to improve SCM practice through inclusion of risk mitigation measures. We conclude with recommendations for policy development to further strengthen automobile industry resiliency