Using the Reference Shrinkage Curve to Estimate the Corrected Crack Volume of a Soil Layer
To estimate the correct soil crack volume based on the shrinkage geometry factor, in addition to measurements with core samples, one also needs to know the shrinkage curve of the soil matrix without cracks. For such a curve one can use the soil reference shrinkage curve that is only stipulated by intraaggregate clay shrinkage without interaggregate cracking. The objective of this work is to illustrate such use of the reference shrinkage curve and, in addition, to argue the necessity to correct the usual estimates of the shrinkage geometry factor in order to correctly estimate the soil crack vol- ume. The illustration is based on available data and reference shrinkage curves for eight soils.
Modeling of water balance, cracking and subsidence of clay soils
Abstract A general procedure has been developed to model water balance, cracking and subsidence of clay soils. The main feature of this procedure is the introduction of the shrinkage characteristic in addition to the water retention and hydraulic conductivity curves into simulation models. The proposed procedure enables direct calculation of volume changes in dependance on moisture transport. With appropriate assumptions for geometry of swelling and shrinkage, these volume changes are converted into cracking and subsidence. Taking into account the calculated area of shrinkage cracks at the soil surface, together with the maximum infiltration rate of the soil matrix and the rainfall intensity, rainfall is dynamically partitioned in matrix and crack infiltration. In this way bypass flow and resulting rapid rises of groundwater levels in cracked soils can be simulated. The procedure was validated by adapting a model for calculation of transient moisture flow in soils, flowex , into a version applicable on clay soils, flocr . Computations with flocr of subsidence, cracking, groundwater level and top layer wetness of a Dutch basin clay soil during 1985 were in good agreement with field observations. Moreover, the proposed method of bypass calculation is supported by good correspondence between measured and simulated rapid rises of groundwater levels.
Composite monolayer fabrication by an arc-spray process
A single layer (monotape) technique for fabricating complex high-temperature tungsten-fiber-reinforced superalloy composites is proposed. The fabrication of sheets of arc-sprayed monotape 38 cm wide and 122 cm long has been demonstrated. Composites fabricated using the method are shown to have equal tensile strength and a cleaner matrix than composites fabricated from powder metal cloth monotapes, and the present technique is less expensive than the powder metal fabrication techniques.