Consolidation behavior of cement—and lime／cement—mixed column foundations

The consolidation behavior of mixed in place cement and lime/cement mixed column was studied. Consolidation of the composite foundation was modeled as a three dimensional axi symmetric problem. The authors used the finite difference method to obtain the pore pressure variation with time at any location below the surface. A computer program developed by the authors was used to draw some interesting conclusions about the consolidation behaviors of cement and lime/cement mixed pile foundation. Finally, a combined model including the permeability coefficients of cement mixed piles and soil, was studied and its feasibility was evaluated.

A numerical evaluation of continuous backfilling in cemented paste backfilled stope through an application of wick drains

Cemented paste backfill （CPB） is gaining popularity in many underground mines worldwide. Sufficient water is added into CPB to make a flowable material for pipe transportation. Barricades are built near the drawpoints to prevent in-rush of the fill slurry. To avoid barricade failures resulting from excessive backfill pressures, backfilling is typically performed with a plug pour followed by a final pour. The interval between the two pours should be shortened or removed to increase mining productivity and avoid pipe clogging. Recently, Li proposed to apply wick drains in backfilled stopes to promote drainage and consolidation. The preliminary simulations by considering an instantaneous filling indicated that the drainage of CPB can be significantly accelerated by using wick drains. Barricade was not considered. Here, some new numerical modeUings are presented with more representative filling sequences, stope geometry, and different draining configurations. The results illustrate that the stope can be backfilled continuously by using wick drains.

Analysis on mechanism and key factors of surrounding rock instability in deeply inclined roadway affected by argillation and water seepage

Based on the characteristics of surrounding rocks for deeply inclined roadway affected by argillation and water seepage, a structure model of layer crack plate was established to analyze the shear sliding instability mechanism. Through solid mechanics analysis of anchored surrounding rock with defect from water seepage, combined with numerical analysis for instability mechanism under water seepage in deeply inclined roadway, key factors were proposed. Results show that with increasing height of layer crack plate, lateral buckling critical load value for high wall of the roadway decreases; there is a multistage distribution for tensile stress along the anchor bolt with defect under pulling state condition;groundwater seepage seriously affects the strength of surrounding rock of the roadway, to some extent the plastic zone of the high side rises up to 8 m. Finally some support strategies were proposed for the inclined roadway and successfully applied to Haoyuan coal mine in Tiela mining area,western China.

Phytoextraction of Nickel and Chrome in Paddy Soil Amended With Municipal Solid Waste and Sewage Sludge

A field study was conducted in the paddy soil amended with municipal solid waste （MSW） and sewage sludge （SS） to find out total, DTPA extractable nickel （Ni） and chrome （Cr） in soil and their uptake by rice plant as split-plot arrangement based on randomized complete block design with three replications. The results indicated that the most available Ni （2.10 ppm） measured under 3 years application of 40 ton.ha~ MSW＋I/2 chemical fertilizer （CF）. Also, with 3 application of 40 ton-ha＂l MSW concluded the highest available Cr. The most accumulation of Ni in root （14.51 ppm） and grain （8.89 ppm） happened under 3 years application of 40 ton.ha-1 SS and 20 ton ha-1 MSW＋I/2 CF, respectively. With application of 40 ton.ha-1 SS and 40 ton SS＋1/2 CF, respectively happened the maximum Cr uptake by root and grain （12.43 and 3.65 ppm, respectively）.

Flocculation of the Moroccan phosphates slimes

In Morocco, the phosphate industry generates by washing during the ore beneficiation in humid way, big quantities of sludge loaded in fine mineral particles （or slimes） with contents of water in the order of 90-95%. The specific consumption in water for the beneficiation of one tone of dry ore is approximately 0.6 m3. The management of this sludge and the recycling of process water are played to a schema of solid-liquid separation by flocculation, settling then stocking in basins of several dozens hectares. Recovered clear waters are recycled into the circuit of washing. The principal motivation of this work which is a part of EL MAA project is dedicated to the study of the impact of the speed of agitation on the flocculation behavior in terms of dewatering of the phosphate slimes and recycling of the process water. Study was driven on sample of slimes taken in entrance of the thickeners of a Moroccan washing plants, before flocculation. The raw slimes have a concentration in solid of 75.5 g·L^-1, a P205 grade of 17.3% and a free settling velocity 9 cm·h^-1. Fine fraction -2 μm, responsible for the poor settling of slimes is composed in practice of nearly 96% of smectite. It represents 9% of the dry solid content in the slimes. Measurements reveal important variations of the granulometric and textural properties of large floes in response to flocculation, opening ways of optimization for the velocity gradient.