Dilatancy Behavior in Constant Strain Rate Consolidation Test
DOI:
https://doi.org/10.5614/jts.2006.13.2.1Keywords:
Lempung, Uji konsolidasi, Dilatansi, Pemampatan sekunder, Efek waktu.Abstract
Abstrak. Sekalipun uji konsolidasi kecepatan regangan tetap (CSRC) memperlihatkan sebagai salah satu tipe yang menjanjikan dari uji konsolidasi cepat, ketergantungan waktu pada respons tegangan-regangan seperti pemampatan sekunder belum cukup menjelaskan terhadap uji CSRC. Berdasarkan pembentukan kembali tanah lempung muda, paper ini menunjukan perilaku ketergantungan waktu yang besar dari uji konsolidasi standar (SC) dan CSRC, dijelaskan secara sistimatis dengan asumsi sederhana yakni ketergantungan waktu dilatansi. Pada uji SC tahapan awal dari tiap penambahan beban ada sedikit dilatansi dan dilatansi mulai terjadi beberapa menit setelah step pembebanan. Pada akhir dari masing-masing langkah pembebanan, dilatansi terjadi secara proporsional dengan pertambahan logaritma waktu, dimana dapat diamati sebagai pemampatan sekunder. Pada uji CSRC, beberapa periode waktu setelah keadaan tegangan memasuki daerah konsolidasi normal, dilatansi cenderung terjadi secara cepat dengan pertambahan ratio tegangan. Sejak sebagian besar dilatansi terjadi pada tahap awal konsolidasi, sedikit dilatansi terjadi diakhir tahapan proses CSRC. Kecendrungan ini membuat spesimen lebih kaku dengan perjalanan waktu, dan membuat tegangan vertikal dan tegangan pori bertambah cukup besar pada bagian akhir proses CSRC. Penentuan perilaku tersebut dapat efektif dijelaskan dengan benar pada hasil uji CSRC.Abstract. Although the constant strain rate consolidation (CSRC) test appears to be one of the most promising types of rapid consolidation test, the time dependency in stress-strain response such as the secondary compression has not been sufficiently clarified yet in CSRC test. Subjected to remolded young clay, this paper shows that a lot of time dependent behavior in the standard consolidation (SC) and CSRC tests is represented systematically by a simple assumption concerning the time dependency of dilatancy. In the SC test, at the first stage of each loading step little dilatancy takes place and dilatancy begins to occur several minutes after step loading. At the latter of each loading step, dilatancy occurs proportionally with the logarithm of elapsed time, which is observed as the secondary compression. In CSRC test, some time period after the stress state has entered the normally consolidated region, dilatancy tends to occur rapidly with the increase in stress ratio. Since most of dilatancy has taken place at the earlier stage of consolidation, little dilatancy occurs at the latter stage of CSRC process. This tendency makes the specimen stiffer with the passage of time, and makes the vertical pressure and pore pressure increase substantially at the last stage of CSRC process. Consideration to such behavior may be effective to correctly interpret the result of CSRC test.
References
Akai, K. and Tamura, T., 1978, " Numerical Analysis of Multi-Dimensional Consolidation Accompanied with Elasto-Plastic Constitutive Equation" , Proc. JSCE, No. 269, pp. 95-104 (in Japanese).
Arai, K., 1985, "Representation of Soft Clay Behavior Based on Minimization of Dissipated Energy" , proc. 5th International Conference on Numerical Methods in Geomechanics, Nagoya, Vol. 1, pp. 277-284.
Arai, K., 1994, "Relationship Between Time Effects in Triaxial Test and Secondary Compression" , Soils and Foundations, Japanese Geotechnical Journal, Vol. 34, No. 3, pp. 59-69.
Janbu, N., Tokheim, O. and Senneset, K., 1981, "Consolidation Tests with Continuous Loading" , Proc. 10th Int. Conf. Soil Mech. and Foundation Engineering, Stockholm, 1, pp.645-654.
Crawford, C.B., 1964, "Interpretation of The Consolidation Test" . J. Soil Mech. Fdns Div., Am. Soc. Civ. Engrs 90, No. SM5, pp. 87-102.
Leroueil, S., Kabbaj, M., Tavenas, F. and Bouchard, R., 1985, " Stress-Strain-Strain Re Relation for The Compressibility of Sensitive Natural Clays" , Geothechnique, Vol. 35, No.2, pp.159-180.
Lee, K., 1981, "Consolidation with Constant Rate of Deformation" . Geotechnique, 31, No. 2, pp.215-229.
Kita, A, Arai, K Machihara, H, and Sompie, B., 1998, "Numerical Analysis of Constant Rate of Strain Consolidation Test" , proc. 53th Japan National Conference on Civil Engineering, Gifu, Vol. 1, p. 416 (in Japanese).
Sompie B, Arai, K and Machihara, H., 2001, "Time Effects in Constant rate of Strain and Constant Loading Rate Consolidation Tests" , proc. 36th Japan National Conference on Geotechnical Engineering, Tokushima, Vol. 1, p. 979 (in Japanese).
Murakami, Y., 1987, "Consideration on The Methods for Estimating The Coefficient of Permeability of A Clay" , JSSMFE, Vol. 27, No. 3, pp 167-170 (in Japanese).
Nagaraj, T. S., Pandian, N. S., and Narashima Raju, P. S.R., 1994, "Stress-State Permeability Relations for Overconsolidated Clays" , Geotechnique 44, No. 2, pp 349-352.
Otha, H., 1971, "Analysis of Deformations of Soils Based on The Theory of Plasticity and Its Application To Settlement of Embankments" , Dr. Eng. Thesis, Kyoto University.
Smith, R. E. and Wahls, H. E., 1969, "Consolidation Under Constant Rates of Strain" . J. Soil Mech. Fdns Div., Am. Soc. Civ. Engrs 95, No. SM2, pp. 519-539.
Shibata, T., 1963, "On The Volume Change of Normally Consolidation Clays" , Annuals, Disaster Prevention Research Institute, Kyoto University, No. 6, pp. 128-134 (in Japanese).
Yin, J. H. and Graham, J., 1988, " Viscous-Elastic-Plastic Modeling of One Dimensional Time-Dependent Behavior of Clays" , Canadian Geotechnical Journal, Vol. 26, pp. 199-209.
Znidarcic, D., Shiffman, R. L., Pane, V., Croce, P., Ko, H.Y. and Olsen, H.W., 1986, "The Theory of One-Dimensional Consolidation of Saturated Clays: Part V" , constant rate of deformation testing and analysis. Geotechnique, 36, No. 2, pp.227-237.
Wissa, A.E.Z., Christian, J.T., Davis, E.H. and Heiberg, S., 1971, "Consolidation at Constant Rate of Strain" , J. Soil Mech. Fdns Div., Am.Soc. Civ. Engrs 97, No. SM10, pp.1393-1413.
