How Credible is Consoldation Settlement Calculation using Ch values.
How Credible is Consoldation Settlement Calculation using Ch values.
(OP)
I am doing settlement analysis and have Cv from Oedometer Test as well as Ch from CPT. The Cv obtained through Ch from CPT is noticeably different from Cv of Oedometer test. Are there any professionals who have practically derived Cv values from Ch values. Most of the research I have done shows papers that err on the academic side with the intention to promote CPT procedure. Calculation of the 90% time for settlement using Cv derived from Ch gives considerably shorter times (5 to 50 times shorter depending on the Kh/Kv value). That makes me hesitant to derive Cv from Ch instead of uemploying Cv from Oedometer test, although it would offer an excellent opportunity to decrease the tiome of settlement and avoid ground improvement options.
One concern is that the Ch was obtained under certain overburden pressure during the CPT operation. When we load the clay (change the effectice stress) one cannot guarantee that the Ch value will remain the same, can he/she? However during osedometer test we allow changes in the effectiive stress. Of course one may say that in Oed test we assume that the permeablity is constant throughout the test.
One concern is that the Ch was obtained under certain overburden pressure during the CPT operation. When we load the clay (change the effectice stress) one cannot guarantee that the Ch value will remain the same, can he/she? However during osedometer test we allow changes in the effectiive stress. Of course one may say that in Oed test we assume that the permeablity is constant throughout the test.





RE: How Credible is Consoldation Settlement Calculation using Ch values.
RE: How Credible is Consoldation Settlement Calculation using Ch values.
RE: How Credible is Consoldation Settlement Calculation using Ch values.
No macrofabric or slightly developed macrofabric (homogeneous deposit)0.67 to 1
Fairly well to well developed macrofabric (eg. sedimentary clays with discontinuous lenses and layers of more permeable material)0.25 to 0.5
Varved clays and other deposits containing embedded and more or less continuous permeable layers
0.07 to 0.33
Jamiolkowski, M. Ladd, C.C., Germaine, J.T. and Lancelotta, R. 1985. New developments in field and laboratory testing of soils. State-of-the-art report. Proceedings of the 11th International Conference on Soil Mechanics and Foundation Engineering, San Francisco, 1, pp.57-153, Balkema Pub., Rotterdam.
RE: How Credible is Consoldation Settlement Calculation using Ch values.
RE: How Credible is Consoldation Settlement Calculation using Ch values.
RE: How Credible is Consoldation Settlement Calculation using Ch values.
One may assume that during the dessipation test in CPT operation water may travel vertically near the cone location and it would be desirable to know, if this is the case, how much it could affect the Ch values. Thank you for your time.
RE: How Credible is Consoldation Settlement Calculation using Ch values.
RE: How Credible is Consoldation Settlement Calculation using Ch values.
RE: How Credible is Consoldation Settlement Calculation using Ch values.
RE: How Credible is Consoldation Settlement Calculation using Ch values.