Study on the base and subbase method of agricultural road. 1; On the resilient modulus characteristics of the subgrade and cement treated base

The characteristics of resilient modulus (Mr) which dominates the life of pavement and the design of pavement were investigated on the test specimens which were cement treated and non-treated of the three different soil types. The resilient modulus was decreased by increasing the cyclic deviator stress (sigma d), especially the resilient modulus was gradually decreased or sometimes increased when the value of sigma d was greater than 0.75-1.0Kg/cm** (2). The resilient modulus was increased by increasing the homogeneously confined stress (sigma do) and such phenomena were distinct on the coarse soils. The resilient modulus was increased by increasing the ratio of confined stress (Kc), and this phenomena were eminent on the coarse soils too, and the higher permanent strain was shown by increasing the value of Kc. In the drained cyclic triaxial compression test, the value of sigma d, Kc, and (sigma do) was introduced by the following interrelated equations which were similar to the Mr model of Cole. Mr/Kcn= k1 (J2/Toct)** (K2)......(coarse soil) Mr/Kcn= K3 (sigma dp/Ti)** (K4)...... (fine soils). The stress path was not much affected by the value of Mr however, moisture content, dry density, and content of fines affected the value of Mr. In the soil-cement specimens, the resilient compression strain (epsilon d) was decreased by the increment of the sigma ho, and Mr was decreased by increasing the sigma d. In the flexible pavement, the cement treated layer should be designed not to fail by the fatigue before the designed traffic load, and actually the pavement could cover the traffic load to a certain extent under the post-crack phase, therefore further studies on these phenomena are required in the design analysis. The finite element computer program (ANALYS) was used for displacement analysis of pavement containing the cement-treated layer. The result showed that the program used for this analysis was proved to be usable