A note on the measurement of travel times using bender and extender elements

By using the bender and extender elements tests, the travel times of the shear (S) and the primary (P) waves were measured for dry sand samples at different relative densities and effective confining pressures. Three methods of interpretations, namely, (i) the first time of arrival, (ii) the first peak to peak, and (iii) the cross-correlation method, were employed. All the methods provide almost a unique answer associated with the P-wave measurements. On contrary, a difference was noted in the arrival times obtained from the different methods for the S-wave due to the near field effect. The resonant column tests in the torsional mode were also performed to check indirectly the travel time of the shear wave. The study reveals that as compared to the S-wave, it is more reliable to depend on the arrival times' measurement for the P-wave. (C) 2010 Elsevier Ltd. All rights reserved.

A note on the measurement of travel times using bender and extender elements

By using the bender and extender elements tests, the travel times of the shear (S) and the primary (P) waves were measured for dry sand samples at different relative densities and effective confining pressures. Three methods of interpretations, namely, (i) the first time of arrival, (ii) the first peak to peak, and (iii) the cross-correlation method, were employed. All the methods provide almost a unique answer associated with the P-wave measurements. On contrary, a difference was noted in the arrival times obtained from the different methods for the S-wave due to the near field effect. The resonant column tests in the torsional mode were also performed to check indirectly the travel time of the shear wave. The study reveals that as compared to the S-wave, it is more reliable to depend on the arrival times’ measurement for the P-wave.

Design and administration of activity-travel diaries: a case study from Bengaluru city in India

Studies on travel survey instrument design and administration in the context of Indian cities are limited despite the fact that these aspects of travel survey face unique challenges here when compared to the cities in the developed world. Here we report results of a pilot survey conducted for evaluating the performances, alternative diary formats and survey administration techniques in Bengaluru city, India. The study proposes two diary formats. `Diary-1' is in day-planner format and is a variant of the one reported earlier in the literature. `Diary-2' is derived as a combination of `Diary-1' and the trip-based diaries widely applied in Indian cities. `Face-to-face', and `drop-off and pick-up' methods of survey administration are considered for retrieving the activity-travel information of individuals. Evidence appears to be strong that diary-2 is preferable to diary-1 for collecting the travel details of individuals. The comparison of the retrieval methods suggests that the face-to-face method of instrument administration is superior to the drop-off and pick-up method in terms of higher response rates and minimum recording errors.