Preconsolidation stress ( σP) is the maximum effective stress that a soil has suffered throughout its life. From a geotech- nical point of view, pre-consolidation stress has great importance because it separates el...Preconsolidation stress ( σP) is the maximum effective stress that a soil has suffered throughout its life. From a geotech- nical point of view, pre-consolidation stress has great importance because it separates elastic and reversible deformations from inelastic and only partially irreversible deformations and marks the starting point of high compressibility. In this study we calculated the preconsolidation stress for 72 undisturbed soil samples from the Yellow River Delta, using the oedometer test and applying the method proposed by Casagrande. The results showed that the over-consolidation ratio (OCR-the ratio of pre-consolidation stress to current natural overburden stress) values of the soil from soil surface to 6m depth varied from 1.72 to 15.34 and the maximum pre- consolidation stress was above 200 kPa. In consequence, the soils of the Yellow River Delta are highly over-consolidated within the upper 6m, the OCR decreasing gradually with depth from 6 to 12m. For samples from deeper than 12m the soils were found to be under-consolidated, which was proved by standard penetration tests (SPTs). The main causes of this type of consolidation are the mineral composition and the designability of the soil body.展开更多
One dimensional laboratory consolidation test was conducted on compacted lateritic soils treated with up to 16% rice husk ash (RHA), to assess its consolidation properties. Specimens were prepared at three different m...One dimensional laboratory consolidation test was conducted on compacted lateritic soils treated with up to 16% rice husk ash (RHA), to assess its consolidation properties. Specimens were prepared at three different moulding water contents (2% dry of optimum, optimum moisture content and 2% wet of optimum) and compacted using the British Standard Light compactive effort. Preliminary tests on soils showed improved index properties with an increase in liquid limit (LL), an increase in plastic limits (PL) with a resulting decrease in plasticity index (PI). Preconsolidation pressure increased with RHA content, it also decreased before increasing with increased moulding water content. Reductions in compression index (Cc) and Swell Index (Cs) with increased RHA content were recorded. Cc and Cs generally decreased before increasing with increased moulding water content. The coefficient of volume compressibility (Mv) decreased and increased with higher RHA content;they were also affected by the soil particle state with increasing pressure. The coefficient of consolidation (Cv) showed no observable trend with increased RHA content but generally increased with higher consolidation pressure on the dry and wet side of optimum compacted states.展开更多
基金supported by the National Natural Science Foundation of China (Nos. 40472137 and 40606020)
文摘Preconsolidation stress ( σP) is the maximum effective stress that a soil has suffered throughout its life. From a geotech- nical point of view, pre-consolidation stress has great importance because it separates elastic and reversible deformations from inelastic and only partially irreversible deformations and marks the starting point of high compressibility. In this study we calculated the preconsolidation stress for 72 undisturbed soil samples from the Yellow River Delta, using the oedometer test and applying the method proposed by Casagrande. The results showed that the over-consolidation ratio (OCR-the ratio of pre-consolidation stress to current natural overburden stress) values of the soil from soil surface to 6m depth varied from 1.72 to 15.34 and the maximum pre- consolidation stress was above 200 kPa. In consequence, the soils of the Yellow River Delta are highly over-consolidated within the upper 6m, the OCR decreasing gradually with depth from 6 to 12m. For samples from deeper than 12m the soils were found to be under-consolidated, which was proved by standard penetration tests (SPTs). The main causes of this type of consolidation are the mineral composition and the designability of the soil body.
文摘One dimensional laboratory consolidation test was conducted on compacted lateritic soils treated with up to 16% rice husk ash (RHA), to assess its consolidation properties. Specimens were prepared at three different moulding water contents (2% dry of optimum, optimum moisture content and 2% wet of optimum) and compacted using the British Standard Light compactive effort. Preliminary tests on soils showed improved index properties with an increase in liquid limit (LL), an increase in plastic limits (PL) with a resulting decrease in plasticity index (PI). Preconsolidation pressure increased with RHA content, it also decreased before increasing with increased moulding water content. Reductions in compression index (Cc) and Swell Index (Cs) with increased RHA content were recorded. Cc and Cs generally decreased before increasing with increased moulding water content. The coefficient of volume compressibility (Mv) decreased and increased with higher RHA content;they were also affected by the soil particle state with increasing pressure. The coefficient of consolidation (Cv) showed no observable trend with increased RHA content but generally increased with higher consolidation pressure on the dry and wet side of optimum compacted states.