Reduction In Void Ratio Research Articles

マサ地盤の圧縮性に関する研究 : 第 II 報圧密試験機を用いた拘束圧縮試験

To clarify the compressibility of Masa-do, it is necessary to test undisturbed samples. In this paper, Masa-do is tested by confined compression tests on the undisturbed samples. The compressibility is closely related to initial void ratio. The results of the tests are summarized as follows : (1) The compression curve plotted in an e-log p coordinate system is discribed in a wholly smooth convex curve and in this curve precompression load is not obtained. (2) The relation between the reduction of void ratio and the load in semi-logarithmic coordinate diagram indicates an approximately straight line, from which it is possible to obtain an e-log p curve. (3) It is possible to predict the settlement by the two straight lines (C_c and C_c^') bent at the point of p=1.0 kgf/(cm)^2 in the e-log p curve. (4) Creep settlement can approximate a straight line between 8 seconds and 15 minutes, and the ratio of the creep settlement to the total settlement is about 20 percent. Viscosity parameter is related to the initial void ratio but independent of the loading stage. (5) Plotting the measured creep settlement for 100 days' period of logarithmic time indicates a slightly concave curve, which gives the safety settlement against the straight line up to the 15 mimutes and the samples with high initial void ratio show a tendency to safety. (6) Several of the samples are divided into two specimen and they are tested under saturated and unsaturated conditions and there is no significant difference between the former and the latter.

Effect of freezing and thawing on the permeability and structure of soils

The permeability and structure of four fine-grained soils were observed to be changed by freezing and thawing. In all cases freezing and thawing caused a reduction in void ratio and an increase in vertical permeability. The increase in permeability is attributed to the formation of polygonal shrinkage cracks and/or to the reduction of the volume of fines in the pores of the coarse fraction, the mechanism controlling the process depending on material type. No definite relationships are established; however, it appears that the largest increase in permeability occurs for the soil of highest plasticity.

Subaqueous Slump Structures

Curved, grading into planar, discordant slump scar surfaces are not uncommon in sedimentary rocks. It is suggested that the slump movement took place penecontemporaneously with the processes of sedimentation and in response to loading imbalances due to the presence of a slope. The curvature of the slump surface may be derived by resolving the vector representing the displacement, or offset, and relating its vertical component to the volume decrease associated with void ratio reduction. The particular shape of the surface is largely a function of the clay mineral content of the sediments.

The Fabric of Anisotropically Consolidated Sensitive Marine Clay

The relationship between soil fabric and the anisotropic consolidation characteristics of a sensitive, highly flocculated marine clay has been studied using x-ray diffraction techniques. Measurements of the clay particle parallelism (fabric) were performed on “undisturbed” and remoulded samples of Leda clay from Ottawa, Canada, in an attempt to determine the influence of sample disturbance on soil fabric and laboratory consolidation test results.The amplitudes of the 10 Å clay peaks of the “undisturbed” natural clays, measured in the major principal plane, increased from about 11 counts/second at low consolidation pressures to about 40 counts/second at 64 tons/sq. ft. This is interpreted as resulting from reorientation of many of the clay platelets into the plane perpendicular to the direction of the consolidation pressure. An abrupt reorientation occurred when the pre-consolidation pressure was exceeded.Remoulding the clay apparently causes a marked breakdown of the interparticle bonds as evidenced by stronger 10 Å peaks and inferred greater particle parallelism at any given consolidation pressure within the range studied. This increase in parallelism is associated with a pronounced reduction in void ratio when compared with the “undisturbed” clay.