Research for determining the dynamic and static strength of some soil types in hanoi by triaxial compression tests

摘要

Dynamic loads are very complicated, while soil types are very varied, therefore their behaviorrnmust be evaluated based on various dynamic test schemes to limit certain conditions of their mutualrninteraction process. We have developed two test schemes for determining the dynamic strength characteristicsrnof soils on triaxial compression test, compared the testing results between those two schemes andrnwith the static strength characteristics: Scheme 1: Fixing the initial stress and pulse frequency, in thernmean time increasing the dynamic load amplitude to cause the soil specimen fail to get the cyclic dynamicrnstrength. Scheme 2: Keeping the constant dynamic state and increasing the static load until the specimenrnfails to get the strength value, which we recommend to call "critical dynamic strength". We have carriedrnout tests for several different soil types and have drawn the following some remarks: For soft soils, theirrndynamic strengths are always lower than their static strengths. Strength decrease under dynamic cyclingrnloadings is highest for soils without structural cohision such as fine sands, dust sands, clayey sands orrnsolis with low structural coshision such as silts, liquidation clay. Dynamic strenght is always much decreasedrnwith the increase of pulse frequency. Main reason is that the destruction of soil structure under dynamic loadingsrncauses the decrease of strength.