ソイルセメントの荷重変形特性に関する二, 三の考察

抄録

Compacted soil-cement has come to be used as a road construction material in recent years. The mechanical property of soil-cement has been investigated. However, only a few experimental works have been made as to the deformation mechanism of soil-cement. Hence, this paper reports some results of the investigation on the deformation mechanism of soil-cement. In this study, the deformation characteristics of soil-cement was considered from the following three aspects.
(1) Stress-strain relation under short time loading
(2) Strain-time relation under constant stress
(3) Deformation characteristics under dynamic stress
The soil-cement dealt with in this paper is the one in a narrow sense, and contains more cement than the so-called“cement-modified soil mixture.”The cement used was normal portland cement, and the soil aggregates used was from the hills in Kyoto. The compacted soil-cement specimens were stored for a certain period in a moist room at 80 percent relative humidity and approximately at 20°C. The test specimens subjected to the sustained load were 32cm high, with 8cm diameter cylinders, and other specimens used in the dynamic test were 30cm high, with 10cm diameter cylinders. The loading apparatus was Amsler type compression testing machine, and in the creep tests the sustained load was applied by means of the spring type loading rigs. Repeated stresses were applied by a low frequency loading machine. The deformation of the soil-cement cylinder in the creep test was determined by means of a 10 in. Huggenberger strain gage and the strain in a short time compression test by means of an electric resistance strain gage.
The results obtained were summarized as follows:
(I) The short time stress-strain relation of soil-cement
The stress-strain curve of the soil-cement, composed of coarse grade soil aggregate, showed a similar characteristics independent of the cement content, or water content. However, the characteristics of the stress-strain curve of soil-cement containing fine grade soil aggregate depends strongly upon the cement content and on the water content.
(II) The creep mechanism of soil-cement
(1) The effect of the water content on the creep deformation characteristics was comparatively small for the soil-cement of coarse grade soil aggregates. However, as to the soil-cement of fine grade soil aggregate, the more water content there is, the more ultimate creep deformation will be made.
(2) The test environment had a considerable effect on the creep deformation characteristics.
(3) Generally the cement content had a little effect on the creep deformation characteristics.
(4) The results of the analysis using the mechanical model showed that the creep deformation of soil-cement was essentially due to the irrecoverable creep deformation with some retardation time.
(III) The deformation characteristics under the repeated loading
The stress-strain curve of soil-cement having no loading history was concave with respect to the strain axis. However the repeated stress changed the above characteristics into a convex curve.