Loose Fill Research Articles

Determination of the Location and Extent of Karst in Limestone with the use of Geophysical Methods

Field studies for testing the usefulness of geophysical methods in the mapping of karst in the northern part of the 'Rheinischen Schiefergebirge' yielded the following results: (1) Geoelectrical resistivity profiling, gravimetry and refraction seismic can be used for the detection of karstified zones. Low apparent resistivities, low p-wave velocities and negative gravity anomalies characterise the loose fill material or highly jointed limestone in these zones; (2) Rapid detection of karstified zones can be carried out with the resistivity profiling technique. The approximate extent of these zones can be mapped. The double dipole (linear) array gives the best results; (3) A more exact determination of the size of the karstified zones can be carried out using refraction seismic and gravimetry. Gravimetry enables an approximate volume estimate whereas refraction seismic allows a more precise volume estimate as well as the determination of the internal structure, nature of material present and boundaries to non-karstified areas.

Fire performance of combustible insulation in masonry cavity walls

The risk of fire spread in buildings, from one room/compartment to another, through cavity walls filled with a range of combustible insulating materials has been investigated. Tests have been carried out on small-scale or storey-high walls having two masonry facings, insulated with typical examples of loose fill, board or in situ foamed plastics products. A small localized penetration of both facings simulating for example an ineffectively sealed air brick was built into the lower part of the experimental wall and two ‘eave’ conditions were investigated viz with the perimeter either sealed or partially open. A small crib was positioned adjacent to the cavity penetration and the subsequent extent of spread of fire and smoke was noted visually; temperature measurements within the cavity were recorded together with heat flux measurements in the combustion zone. The experiments showed the dependence of the extent of fire spread on the air supply to the combustion zone; in this type of wall with the upper perimeter sealed, the risk of flame or smoke spread from one area to another is negligible. With the upper edge partially unsealed, no flame and only negligible smoke spread was noted with in situ foamed insulations. With granular fill, retained in position within the cavity, some smoke percolated upwards but the risk of eventual spread of fire through the eave opening was restricted to three products, which have subsequently been withdrawn from the market. Thermoplastic bead flowed through the hole into the fire area contributing to the fuel load but when installed with an adhesive the bead was effectively maintained in position and performed like the in situ foamed products. It was found with one specific test condition that slow flame spread could be sustained through a continuous cavity adjacent to expanded polystyrene insulating boards provided the eave perimeter of the cavity was unsealed. Whilst such flame spread is unlikely to affect directly any inhabited areas of the building, sealing of cavities insulated with combustible boards is considered to be essential to prevent smoke spread, possible roof fires and destruction of the insulant.

An experimental comparison of forward and reverse smolder propagation in permeable fuel beds

An experimental comparison of forward and reverse smolder propagation is presented; these two cases correspond, respectively, to reaction wave movement in the same and in the opposite direction of the air flow. Two types of permeable fuels were examined, a cellulosic loose fill insulation (wood fibers) and a particulate polymer material (polyisocyanurate). Air flow velocity was varied from 0.04 and 0.77 cm/s in the reverse smolder studies, yielding propagation velocities from 4·10 −3 to 4·10 −2 cm/s; air flow velocity was varied 0.15 to 0.49 cm/s in the forward smolder studies, yielding propagation velocities from 1·10 −3 to 2.5·10 −3 cm/s. Thermocouples and gas sampling (O 2, CO, CO 2) were used to probe the structure of the two types of smolder wave. There are marked qualitative and quantitative differences in the two smolder propagation modes. Reverse smolder quickly reaches a steady propagation rate determined largely by heat transfer processes; forward smolder propagation is unsteady and moves at a lower rate that appears limited by the stoichiometry of char oxidation. Both modes of propagation are ultimately limited by the rate of oxygen supply.

A Study of Boron Additives in Cellulose Insulation

The relationship between the content of boron- containing additives in loose fill cellulose fiber insulation and various performance characteristics was studied. The relative tox icity of the off-gases appeared to decrease with increasing additive content, but the change was not significant at the lower additive levels. The yield of carbon monoxide tended to decrease with increasing additive. The weight of residue generally increased with increasing additive, but the difference between the weight of ini tial additive and the weight of residue varied with the additive content and with the boron compound.

Additive Content and Residue Weight in Cellulose Insulation

The relationship between the content of boron- containing additives in loose fiber fill cellulose insulation and the weight of residue after pyrolysis was studied. The weight of resi due generally increased with increasing additive content, but the difference between the weight of initial additive and the weight of residue varied with the additive content and with the boron com pound.

たばこ刻みの圧縮特性曲線

The purpose of this study was to obtain the relationship between specific volume v and compressive stress P of tobacco shreds during compression and to disclose the influences of experimental factors, physical properties and compressive hysteresis of shreds upon the v-P relation. Experiments were carried out with five experimental factors, that is, the variety of tobacco V (Fluecured V1 and Domestic V2), the leaf position on a stalk p (5 levels), the moisture content w (7∼18% WB), the number of compression N (1∼3) and the loosening of shreds after compression. The experimental data thus obtained were analyzed by means of a statistical method.The important results obtained were as follows:(1) The relationship between v and P of tobacco shreds during compression was able to be shown by the following formula, ln P=K0+K1v.(2) The sign of the direction coefficient K1 was minus, and the absolute value of K1 increased as p decreased or w increased. The absolute value of K1 in V1 was larger than that in V2.(3) The sign of the intercept K0 was plus, and the absolute value of K0 was nearly constant, independent of the condition of V, p and w.(4) The physical properties, which affected the direction coefficient, were the elastic modulus, the specific volume of tobacco itself and the correlative specific volume between shreds after loose fill. Among these properties, the elastic modulus was the most influential one.(5) The increase of N caused stress relaxation and made the absolute values of K0 and K1, higher. The loosening of shreds after compression decreased the degree of stress relaxation.

Combustibility of Loose Fiber Fill Cellulose Insulation: the Role of Borax and Boric Acid

The influence of borax and boric acid on the resistance of cellulose insulation to smouldering and flaming combustion has been examined using material treated by a wet application process. Boric acid has been shown to be required at an add-on level of at least 11.6 parts to 100 parts (by weight) of cellulose if resistance to smouldering combustion by cigarette ignition is to be achieved. In order to increase the resistance of the material to flaming combustion, however, it has been shown that borax is required in the formulation. Moreover, in order to maintain the resis tance to smouldering combustion it has been found necessary subsequently to increase the add-on of boric acid. The relationship between the amount of boric acid required to maintain resistance to smouldering combustion while providing for resistance to flaming combustion with borax is given by: boric acid required (pph) = 11.6 + [0.185 × (borax used)]

Liquefaction during 1906 San Francisco Earthquake

Liquefaction-induced ground failures caused major damage during the 1906 San Francisco earthquake. An analysis of published reports shows that lateral-spreading landslides were the most pervasive and most damaging type of ground failure associated with liquefaction. Bridges, roadways, pipelines, and buildings suffered considerable damage. Pipeline failures were particularly critical in San Francisco, cutting off the water supply to the city and thus indirectly contributing to the substantial post earthquake fire damage. Flood plain, deltaic, and loose sand fill deposits were particularly vulnerable to lateral spreading failure. Recent borehole data from four lateral spreading locations show that loose, saturated sand underlies each site at shallow depths. Flow landslides developed on several sandy slopes but did little damage because of sparse development in the affected areas. No clear evidence of bearing capacity failures beneath buildings was found; however, settlement of several embankments may have been a consequence of liquefaction. In several instances ground failures caused by liquefaction have recurred at the same location during successive large earthquakes.

Soil melting-a practical trial : 8F. TUNNELS AND TUNELLING, V7, N1, JAN–FEB. 1975, P44–45

The article describes the subterrene system designed for tunnelling in loosely compacted formations in which a glass lining is formed to support a tunnel roof either as a temporary or a permanent measure. In tests the roof and sides of an experimental tunnel were formed by melting a series of 50mm diameter horizontal holes approximately 2M deep in a loose fill material using electrically heated consolidating subterrene penetrators. The holes were sufficiently close for the glass linings to fuse and so produce a double walled lining reinforced by webs. After tunnel roof and walls were formed, the fill material could be excavated by hand. A long-term development of this system includes equipment to melt a continuous kerf around the periphery of a tunnel being constructed in unconsolidated material so that the melt would be deposited in the form of a thick glass tunnel lining. /TRRL/

Structural Behavior of Buried Plastic Pipe

This investigation is a study of some of the factors which affect the ability of a plastic pipe to support earth loads. Some of the factors that were considered are the strength of the pipe and the soil conditions.Two series of laboratory tests, using two soil densities, were conducted on two types of plastic pipes that had six wall thicknesses. Deflection gauges were used to measure changes in the inside diameter due to an external load that was applied on the buried specimens.The results indicated that loose soil fill will produce about 70% more vertical deflection in a pipe than dense soil fill. Also, it was observed that vertical deflections can best be assessed by considering the resistence of the pipe to membrane forces rather than bending moments as stipulated in the A.S.T.M. Specifications.

Heat Transmission in Cellulosic Fiber Insulation Materials

Abstract Measurements of heat transmission in a number of different loose fill cellulosic insulations have been made by heat flow meter and guarded hot plate methods. Effect of temperature and density have been studied together with a limited investigation on moisture effects. Variations of up to 18 percent occur in the same nominal materials from different sources. This fact indicates that the raw materials and their processing can have a significant influence on the heat transmission properties. For the optimum density range of 35 to 40 kg/m3 and above, the different materials have a very similar temperature coefficient of thermal conductivity. Lower density materials have a significant radiation contribution to their total heat transmission characteristics.

Experimental Investigation on Influence of Elastic Modulus on Filling Capacity of Shredded Tobacco

The filling capacity of shredded tobacco is related with its resistance to compression and its specific volume. Therefore, it is assumed that the filling capacity (FC) is constituted by three factors, that is, the elastic modulus of tobacco (E), the specific volume of leaf self of tobacco (VM) and the relative bulkiness of tobacco shreds at a loose fill (VP). For the purpose of representing relationships among those four variables, quantitatively, the following multiple regression formula was statistically calculated with many experimental data obtained on typical varieties of natural tobacco cultivated in Japan.(FC)=C1+C2+C3VP+C4VMThe results obtained are as follows:(1) The influence of E on FC was greater than that of VP or VM, VP and VM had similar influence on FC.(2) The esimated precision of other regression formula using VQ (the relative bulkiness of shreds at an initial moment of pressure generation) in place of VP was better than that of the above-mentioned fomula using VP.(3) Similar consequences as (1) and (2) were achieved from other calculation using EG (the elasticity per unit dry weight), VA (the total bulkiness at a loose fill of shreds, VA=VP+VM), VB (the total bulkiness at an initial moment of pressure generation VB=VQ+VM) in place of E, VP, VQ and VM.(4) In conclusion, it was confirmed that the investigation of E is indispensable to analyze FC.

Effect of the cross-sectional shape of tunnels on the distribution of contact pressures

1. When determining the earth pressure on timbering of tunnels constructed by the cut-and-cover method it is necessary to distinguish two cases of the joint action of the structure and enclosing soil: in a trench and in made ground. Structures for which the condition Hf/Bt≥0.5 can be referred to the first case and Hf/Bt 0.5 B it is necessary to take into account the concentration of pressure caused by the different deformability of the structure and enclosing soil. In calculations of vertical pressure from clay fill it is necessary to take into account cohesion which is restored as the soil is compacted. 2. The distribution of stresses along the foot of the tunnel in the case of weak soils can be taken in calculations in the form of a rectangular diagram. For bases having high values of shear resistance it is necessary to take into account the concentration of pressure on the edge portions of the bottom and take the distribution of pressure on the foot to be saddle-shape in accordance with the recommendations given in [3]. 3. The horizontal pressure on the walls of tunnels in a trench can be assumed uniformly distributed over the height with an intensity equal to 0.25–0.3 of the acting vertical pressure on the ceiling in the case of layerwise compaction of the fill in the pockets and 0.2 of the acting vertical pressure in the case of loose fill; for structures in made ground it is taken as the active pressure according to Coulomb's theory. 4. The indices of the physical and me chanical properties used in calculations of the pressure of soil fills should be designated on the basis of engineering-geologic investigations of the disturbed soil carried out with consideration of the conditions and methods of placing the fill.

Thermoplastic Extrusion- a Method to Produce Starch-Based Loose Fill Packaging

Bioplastic materials, where starch-based loose fill packaging can also be included, play an important role in the evolution of modern science and civilisation. As they have unbeatable benefits as compared to classical synthetic plastic materials, they are more and more used. This paper presents some aspects of producing loose fill packaging based on starch by means of thermoplastic extrusion, putting an emphasis on the working diagram describing the extrusion mechanism with direct expansion of a partially crystalline polymer and the mechanism of extrudate expansion in its five steps: order-disorder changes, nucleation, extrudate swelling, development of voids and void breaking.