Constrained modulus

The magnitude of the constrained modulus depends on the applied stress, and any given value of constrained modulus will apply over only a limited range of stress and strain. Figure 1 shows constrained modulus values based either on direct measurement, or calculated from compression ratios (CR) reported in the literature as indicated. Some of the outlying values, such as the high modulus values reported in [2], are known to be for old refuse having a high bulk unit weight (18 kN/m3) and a high ash and rubble content. Notwithstanding the outliers, directly measured constrained modulus values, both in the laboratory and the field, lie within the range of compression ratios reported in [3] of 0.08 to 0.41. There is no obvious influence of age on compressibility.