Different Types Of Sand Research Articles

Measurements of the thermal conductivity of clay-sand and clay-graphite mixtures used as engineered barriers for high-level radioactive waste disposal

Thermal conductivity measurements have been carried out on different possible constituents for engineered barriers. These consist of a mixture of selected French clay named Fo-Ca (calcic smectite) and different types of sand and/or graphite. The thermal conductivity of clay-sand mixtures depends, in addition to their bulk density and their water content, on the granulometric distribution of the sand. This conductivity increases with the median diameter of the sand. The thermal conductivity of clay-graphite mixtures is highly dependent on the type of graphite used; in some cases it can be significantly increased by the addition of a small percentage (5 mass%). Under these conditions it is not surprising to find that the increase in the thermal conductivity of ternary clay-sand-graphite mixtures depends, above all, on the graphite content. The present models (geometric model, Maxwell's model) applicable to pure compacted clays cannot be used for these types of mixtures. A specific model that takes the contact resistance between the sand particles and their average size into account has been developed and explains the experimental results for the sand mixtures.

Shear Strength Characteristics of Sand‐Polymer Interfaces

The results are summarized for an experimental program involving over 450 direct shear tests of sand‐polymer interfaces. The interface frictional strength was found to increase with soil density and decrease with the Shore D Hardness of the polymer. The shear strength characteristics were found to vary as a function of the type of sand, but were independent of repeated loading, at least insofar as polyethylene piping and linings are concerned. The shear strength characteristics of a polymer interface can be expressed conveniently as the ratio of the interface angle of friction and the direct shear angle of soil friction, δ/ϕds′. This ratio was relatively constant at 0.55–0.65 along high‐ and medium‐density polyethylene surfaces for different types of sands at various densities. A general model for interface frictional resistance is developed, in which δ/ϕds′ is related to the Shore D Hardness, HD, of the polymer. Limiting conditions for δ/ϕds′ are defined on the basis of theoretical considerations involving the critical state angle of shear resistance, ϕcv′. This model allows for rapid evaluation of interface frictional strength and applies to plastic piping, linings, soil strip reinforcement, and a variety of other soil‐polymer systems.

Modeling Sediment Movement into Perforated Subsurface Drains

ABSTRACT IN order to predict the amount of sediment in subsur-face drain pipes, an analogy was established between the drain cross sectional area occupied by sediment and the amount of granular material that flowed in a confined volume through a perforation before a bridge formed. Experiments were performed using glass beads and eight different types of sand using a permeameter-like apparatus. Various parameters related to the shape and dimension of the perforations and to the particle size distribution of the sands were investigated. Results indicate that a sigmoid model describes more accurately than a linear model the relationships between the amount of material and the various factors related to the geometry of the perforation. For the eight sand types, the amount of material is best predicted (R2 = 0.828) from the hydraulic radius of the perforation and from the D60 of the sand.

Improved method to calculate the critical conditions for drying out sandy soils around power cables

A numerical model has been developed, with which it is possible to calculate the critical thermal conditions at which drying out in sandy soils starts. This model is based on the theory of Philip and de Vries. Comparison of results of calculations with those obtained from extensive experiments on different types of sand shows that there is a reasonable measure of agreement. In particular, this is the result of taking into account both the effect of hysteresis in the relation between water content and suction tension and the effect of temperature upon this relation. It is indicated how the knowledge about these drying-out phenomena can be incorporated in the procedure of determining cable dimensions in practical cases. This knowledge enables quantification of the risk due to thermal runaway, which leads to a more efficient use of buried cables

Effects of Different Types of Sand and Vermiculite Grades on the Test Tube Method for Evaluating Preinoculated Seed1

Combinations of two types of sand and two grades of vermiculite in test tubes (25 × 200 mm) were evaluated for growth of seedlings with root nodules at 21 days of age. Rhizobium‐inoculated alfalfa seeds were planted two per test tube. Each type of sand was suitable for testing provided it was washed free of fine particles. Seedlings grown in substrate combinations which included the vermiculite having smaller (0.32 cm) particle sizes produced fewer nodules regardless of the sand type.

Distinction des sables marins et fluviatiles

Abstract On the basis of analyses of different types of sands from various localities in order to establish criteria for distinguishing sands of marine and fluviatile origin, the general rule is formulated that, if the frequency percentage of grains with a diameter of three millimeters is greater than 30 percent, the sands are unquestionably marine; if the percentage is between 20 and 30 percent, the sands are probably marine. Application of the rule to a study of red sands of the Nantes region, France, demonstrates that the sands are Pliocene marine deposits formed in place, or (less probably) they are composed of Eocene marine material which was reworked in the Pliocene.

PHOSPHATE RETENTION BY SAND IN RELATION TO SEEDLING CULTURE

PHOSPHATES ARE known to be fixed by soil particles and by sand. When complete fertilizers are applied to soil, the phosphorus is one of the last elements to be leached out by rain. Similarly, the addition of nutrient solutions to sand cultures frequently results in retention of some phosphate by the sand. Although phosphates become fixed in a form that is insoluble in water, they still may be available to plants through the activity of the roots. Among the many soil studies on phosphate retention, the work of Ford (1933), Perkins and King (1936), and Beater (1937) may be mentioned. In regard to the sand culture of seedlings, the importance of phosphate retention became evident in connection with certain experiments for the control of damping-off. It was noted that seedlings made as good growth in sand previously used with a complete nutrient solution, washed in water and then supplied only with KNO3, as in new sand with both KNO3 and Ca (H2PO4)2 supplied. Later it was found (Dunlap and Livingston, 1937) that considerable phosphate remained in the moist sand mass in a porous flower pot under continuous subirrigation, even after the K and NO3 had been completely removed by evaporation and water movement. As preliminary experiments, the growth of seedlings in new sand with only KNO3 added was compared with growth in the same kind of sand but with both KNO3 and Ca(H2PO4)2 supplied as plant nutrients. In this way, young plants of celery, lettuce, spinach, and tomato were found to respond markedly to the additional application of Ca(H2PO4)2. On the other hand, barley, cabbage, flax, garden pea, kochia, and zinnia showed little difference in size of the seedlings when Ca(H2PO4)2 was included as a nutrient. In this connection the P-content of seeds is known to vary considerably between different species. This paper reports the results of experiments on phosphate retention by sand as indicated by the early growth of plants from seed. A white, insoluble sand (Berkeley No. 18 mesh, Pennsylvania Glass Sand Corporation), practically neutral in reaction, was used as the culture medium for the plants. Over one hundred cultures of about 125 tomato seedlings each were grown in the greenhlouse at the Connecticut Agricultural Experiment Station during the winter of 1937-1938. There were two series of cultures. The first consisted of new sand entirely, with various nutrients [mostly KNO3 with varying amounts of Ca(H2PO4)2] added. After the plants in the first series were harvested, the same sand was washed and used over again in the second series of cultures to which only KNO3 was added in most cases. Some of the cultures in each series contained sand that had been washed in 8 per cent HCl. In addition to the green' Received for p}ublication October 25, 1938. house cultures, laboratory studies were made to determine the relative rapidity and degree of phosphate retention when different types of sand were treated with solutions of Ca(H2PO4 )2. Except for certain modifications, the method for growing the experimental plants was the same as that described by Dunlap and Livingston (1937). The weights recorded below refer to the total, fresh, stem and leaf material produced by the entire culture 28 days after sowing. Obviously the fresh-weight data obtained from the plants in the first series of cultures was in no way related to phosphate retention by the sand, since pbosphates are available even after fixation. In the first series, cultures without added nutrients and receiving only tap water produced 5.5 gm. of fresh material. Those receiving a single-salt application of 1 gm. (about 0.01 gm.-mol.) of KNO3 per culture produced an average fresh weight of 21.8 gm. Different applications of Ca(H2PO4)2, in addition to the above amount of KNO3, per culture at time of planting gave the following increases in fresh weight: