Abstract Residual sludge from dimension-stone working plants, both from gangue saws with abrasive shot and frame saws, is classified as waste and presents a number of problems for the stone industry. These problems include a fine size distribution, heavy metals and total petroleum hydrocarbon (TPH) content, all of which impede recovery and reuse. Residual sludge, management of which is administered in accordance with the Italian Legislative Decree 152/06, can be used in waste form for environmental restoration or for cement plants. However, it is also possible that sludge applications could go beyond these limited uses with incorporation of systematic treatment for the production of secondary raw materials (SRM), for example, filler, or for ‘new products’, for example, artificial loam. Such new products or SRM have to be certified not only on the basis of their technical and physical characteristics but also by means of appropriate chemical analyses to guarantee that the products are not contaminated. This paper outlines the results from laboratory and in situ characterization of residual sludge. In particular, three potential applications of sludge either by itself or mixed with other materials were evaluated: landfill waterproofing material, filler material for civil works and artificial soil for land rehabilitation.

Abstract The results of three types of laboratory strength tests on undisturbed samples of a saturated clayey soil regolith are analyzed. Drained-direct shear tests, aniso-tropically consolidated-undrained triaxial compression tests with pore pressure measurement, and constant-shear-drained unloading test results indicate different modes of failure and different strength parameters. Based on the grain-size distribution and plasticity test results, it appears that the behavior and strength of the regolith would be dominated by the clay content; however, the results of the strength tests illustrate the soil has a structure formed by cemented bonds. This structure has a larger influence on the behavior and strength than the clay content does, at least at the depth of failure. At the in-situ stress level of the shallow regolith, the consequence of failure is found to be a function of the stress path. As a result, some slope failures may move slowly for short distances, and others many mobilize into rapid flow failures because of differences in the stress path leading to failure.

Abstract Palos Verdes Peninsula contains large landslides in areas that are otherwise desirable for residential development. The landslides can be developed providing the factor of safety is at least 1.5 or can be raised to 1.5 during development. The greatest uncertainty in the calculated factor of safety is the residual shear strength of bentonite that forms the bases of slides. The use of too high a shear strength inflates the calculated factor of safety and can result in landslide failure after development. Tests by various investigators yield a wide range of residual shear strengths for bentonite samples from Palos Verdes Peninsula. Most residual friction angles (4φr) range between 6° and 14° with one lower value (3.5°) and several higher values reported. Residual cohesions (C r ) range mostly between 0 and 36 kPa (0 to 750 lb/ft2). Data for various bentonite samples from Palos Verdes Peninsula indicate they have similar compositions and Atterberg limits. Calcium montmorillonite is the principal clay mineral; the liquid limit is generally between 80% and 110% with the plasticity index between 40% and 70%. The data suggest that much of the reported variation in residual shear strength is the result of differences in sample preparation, testing methods, and interpretation of results rather than true differences in strength. Bulk samples of bentonite from the base of the Portuguese Bend landslide were remolded and tested by conventional direct shear, long sample direct shear, and ring shear devices to determine the effect of testing method on residual shear strength measurements. The three devices gave similar results—for conventional direct shear, φ r = 6.9° and Cr = 33.0 kPa (690 lb/ft2); for long sample shear, tyr = 6.8° and Cr = 23.8 kPa (497 lb/ft2); for ring shear, tyr = 6.7° and Cr = 7.2 kPa (150 lb/ft2). Back calculations indicate the ring shear results most closely simulate the residual strength along the base of the Portuguese Bend landslide. For all those devices, the residual shear envelope is a curve whose slope reaches an asymptote near a confining pressure of 200 kPa (approximately 4,000 lb/ft2). Reported φ r angles are commonly too high because samples were not tested at sufficient confining pressure to define the asymptote and a best fit straight line was drawn through the data points.