Presented in this paper is a study of the effect of compactive effort (CE) and long-term soaking on the strength characteristics of a clayey gypsiferous subgrade soil. The tested soil is A-6 (6) soil according to American Association of State Highway and Transportation Officials (AASHTO) soil classification system. To study the effect of CE and long term soaking on the properties of the tested soil, various California bearing ratio soil samples were prepared and compacted at optimum moisture content of the modified AASHTO compaction, but using four different chosen CEs of 12, 25, 56 and 70 blows/layer and then soaked for 0, 4, 7, 15, 30 and 120 days. The California bearing ratio (CBR) tests indicate that the CBR increases significantly in a nonlinear manner with increasing CE for all soaking periods, indicating improvement in soil strength with increased compaction. The rate of increase dies out with increasing CE. The CBR tests reveal also that there is a serious drop in the CBR due to soaking for all CEs.

Many different factors can influence the outcomes of light-weight deflectometer (LWD) tests. Some of these factors are specific to the type of the used LWD, while others are related to the testing conditions. This paper summarizes the findings of a detailed investigation into the relationships between variables altering the measurements of the light-weight deflectometer test. Field testing was performed to investigate the effect of the sensing configuration (measurement of plate vs ground surface) and testing configuration (in terms of applied load magnitude, number of loadings, and moisture content). To accomplish this objective, a number of in situ LWD and moisture content investigations were conducted on two selected construction materials, namely, sandy subgrade soil and unbound granular material. Considering the multiple influencing factors involved in this study and the material dependency, relationships between the plate deformations and ground deformations could be developed, something which will help in overcoming the standardization problem of various LWD devices and their effect on the compaction control process.

No abstract

Aclay of CH group according to the unified soil classification system (or CV clay according to BS 5930) with about 33% gypsum contentwas tested in the laboratory for the resilient modulus using the ultrasonic wave propagation technique. Forty-eight California bearing ratio (CBR) soil samples were compacted at the optimum moisture content and 95% of modified AASHTO compaction. For each soaking period of 0, 4, 7, 15, 30, 60, 120 and 180 days, three pairs of samples were loaded at 45, 178 and 312 N surcharge load, respectively. The resilient modulus ( M R ) of the gypsiferous soil tested was determined using CBR soil samples before and after each soaking period, and the following observations were made: (1) soakingresults in a progressive decrease in M R with increasing soaking period; (2) after 180 days soaking the resilient modulus decreased by 92%, 85% and 80% relative to the unsoaked condition for CBR samples under surcharge loads of 45, 178, and 312 N, respectively. Furthermore, a strong linear correlation between the resilient modulus and soaked CBR was found. An empirical equation has been developed relating M R at any soaking period to the unsoaked condition, taking into account the effect of soaking period and surcharge load.

No abstract