Journal of Performance of Constructed Facilities

This paper describes an investigation into the effective length of columns subjected to axial loads, for the various conditions encountered during the construction of buildings using the lift-slab method. Many designers of lift-slab construction have assumed an effective length factor, K, for all conditions, equal to 2.0, and have believed that this assumption is reasonable or conservative. The investigation shows that for many conditions a K value equal to 2.0 is reasonable or conservative; however, the investigation also shows conditions where effective length factors greater than 2.0 should be used, and where effective lengths much lower than 2.0 could be used.

This paper presents a comparison study of the experimental results from the falling weight deflectometer (FWD) test, field rigid plate bearing load test, and laboratory resilient modulus test on granular subgrade materials in flexible pavements. The results showed that the average laboratory resilient moduli at optimum compacted conditions were 1.1 times higher than the average laboratory determined resilient moduli at in situ conditions. The FWD back-calculated moduli were about 1.6 times higher than the laboratory resilient moduli for the granular materials. The average laboratory determined maximum dry density was slightly higher than the average field measured in situ dry density. A hyperbolic model was proposed to represent the relationship of the load-deformation curve obtained from the field plate bearing load test. No significant relationship was found between the laboratory resilient modulus and the modulus of elasticity from the field plate bearing tests.

When bored piles are installed through a jet grout layer, significant interaction may take place between the piles and the jet grout. Field load tests have indicated that significant enhancement of the pile shaft capacity and axial stiffness was possible for both compression and tension piles. The influence of the jet grout layer was more pronounced for piles under compression loading compared with uplift loading. The effectiveness of the jet grout in transmitting load via shearing action was dependent on the thickness of the grouted zone, the strength of the interlocks between individual jet grout columns forming the grout slab, as well as the interface bond between the pile shafts and the grout. No apparent adverse effect on the performance of permanent foundations was envisaged as a result of the presence of the jet grout layer. However, interpretation of pile behavior from load tests was complicated by the interaction between the test pile and jet grout, resulting in overprediction of pile capacity and axial stiffness. The significance of the interaction has to be carefully evaluated so that a correct interpretation of the true pile capacity and axial stiffness can be made.

This paper presents a case study of a U-shaped, courtyard house damaged by expansive soils. The field investigation revealed that the damage was caused by edge heaving as a result of water ponding in the courtyard. A back-analysis procedure using finite-element analysis is presented that is based on the measured slab surface levels. The back-analysis provides a representation of the underlying ground movement. The results of the back-analysis compared reasonably well with the actual observations in the field. It was deduced that the slab cracking could have been prevented and the distortion of the house would have been significantly reduced if a strap beam had been added in the courtyard area.

A series of observations, studies, and analyses to be made in the field and in the office are presented to gain a proper understanding of how an embankment dam fits into its geologic setting and how it interacts with the presence of the reservoir it impounds. It is intended to provide an introduction to the engineering challenges of assessment and rehabilitation of embankments, with particular reference to a Croton Dam embankment.

The authors should be congratulated on an interesting paper dealing with residential floor slab flatness. The references to our work are also greatly appreciated (i.e., Day 1990; Marsh and Thoeny 1999). Specific comments are as follows: