dc.contributor.advisor Grimstad, Gustav dc.contributor.author Sletten, Joakim Ripman dc.date.accessioned 2019-09-11T08:15:09Z dc.date.created 2015-06-09 dc.date.issued 2015 dc.identifier ntnudaim:13777 dc.identifier.uri http://hdl.handle.net/11250/2614677 dc.description.abstract Many geotechnical problems requires assumptions regarding the initial stress state in the soil to be made. The earth pressure coefficient at rest, K0, describes the relationship between horizontal and vertical effective stresses. With some knowledge about the soil type and load history, a value is often chosen based on prior observations or internal friction angle. The K0nc is used in soil modeling, both for determining in situ stress level and as a way to represent the anisotropy found in natural clay by rotating the yield surface. Creep causes the soil to exhibit characteristics corresponding to an increased apparent preconsolidation pressure. True overconsolidated clays may have a K0 value well above 1, while a value between 0.4 - 0.6 is typical for normally consolidated clays. The development of the earth pressure coefficient during creep is disputed. Different laboratory tests have yielded different results, showing both increasing and decreasing values as well as a constant value. An oedotriaxial test was performed. A regular triaxial rig was used and the vertical load and cell pressure were regulated manually to maintain zero radial deformation. Four tests with the split ring oedometer was performed. Two of the tests included a creep phase of two weeks, while the other two were run as a standard oedometer with an unloading-reloading sequence. The results are indicating that K$_0$ is nonlinear during one-dimensional compression of Tiller Clay. From an initial high value, it gradually lowers as the vertical effective stress increases. K0 reaches a minimum value of 0.4 at $\sigma_{cv}$. As the clay experiences further destructuration post-yield, K$_0$ stabilizes on a value of about 0.5 at 1.5 - 2 times the preconsolidation pressure. Long term creep tests were performed and K$_0$ was measured over time. Temperature variations greatly affected the results, as the horizontal pressure sensors were very sensitive to changes in temperature. There does not seem to exist an upwards trend, but it is challenging to say with a high degree of certainty. The results show that unloading and reloading will shift the stress ratio away from the original K$_0^{NC}$-line. Upon further loading the stress path will stabilize on another K$_0$-line in the normally consolidated region, parallel with the original line, but at a higher deviatoric stress level. en dc.language eng dc.publisher NTNU dc.subject Bygg- og miljøteknikk, Geoteknikk en dc.title On the Earth Pressure Coefficient at Rest During Creep en dc.type Master thesis en dc.source.pagenumber 81 dc.contributor.department Norges teknisk-naturvitenskapelige universitet, Fakultet for ingeniørvitenskap,Institutt for bygg- og miljøteknikk nb_NO dc.date.embargoenddate 10000-01-01
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