Poor quality fill material

In some cases, poor quality fill material will have to be used. Reference is also made to section 9.1 Cohesive or fine-grained fill materials for a more detailed description on the use of poor quality fill material. A shortage of sand sources in the close vicinity of a project or environmental constraints may have as a consequence that one is forced to work with cohesive materials for the land reclamation. In these cases the shear strength of the fill, and its increase in time, is much more difficult to predict compared to the use of high quality fill materials. A good knowledge of dredging and deposition methods is necessary. 

Sometimes, for the undrained strength, the parameter (p 0) is used. This 

Implications of using poor quality fill material 

The use of poor quality fill materials can have serious implications such as  

for example, very silty fine sand is dredged and hydraulically placed, the material will dewater rather slowly. During the filling operation itself, driving with vehicles over this type of material is not possible. However, when the fill becomes partially saturated or fiiUy dry, it will become a very stable layer. Working with very fine non-cohesive saturated material can be dangerous since this material is sensitive to vibrations and may Uquefy locally as a result of the vibrations of bulldozers and excavators working on site. 

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If quality control after the construction of a reclamation reveals that certain parts do not have the specified fill mass properties then it is occasionally required to remove the poor quality fill material. However, ground improvement could be a viable alternative (in respect of quality, time and cost) to repair these deficiencies without the need to replace the inferior fill by higher quality material. 

The shear strength of a reclamation area is primarily related to the type of fill material used. Distinction is made between high quality fill material and poor quality fill material . 

Some examples of working with poor quality fill material are discussed in section 9.1. 

The assessment of the shear strength of a fill is an evolving process during the design and execution of a hydrauhc fill project. A different approach is followed for high and poor quality fill materials. Generally, following phases can be identified ... 

Poor quality fill Material (silt, clay)... 

Poor quality fill materials (clay, silt)... 

It should be noted that the terms high quality and poor quality do not refer to the quality of the resulting reclamation area. Even with poor quahty fill material, a high quality reclamation area can be achieved, given a proper design. 

The above equation should be used with caution, however, because it does not account for the quality of interfacial contact between the plastic and the filler system. Poor interfacial contact has the same effect as a thermal contact resistance and can result in a significant lowering in the ability of the highly conducting filler particles to transmit heat to the low-conductivity polymer matrix. What complicates the matter further is that these systems may possess good interfacial contact while the polymer matrix is molten but then become lower in thermal conductivity as interfacial contact resistance develops between the filler and the now-solidified polymer. This can be particularly confusing in the case of some filled semicrystalline polymers, where the appearance of the crystalline phase upon solidification should result in increased thermal conductivity, while the actual value appears to decrease. For this reason, it is considered safer to measure the thermal conductivity of filled materials. 

Another cause of failure in PP artefacts is the poor quality of the weld lines. Weld lines are inherent weak positions due to the poor frsion of the material at molecular level. However, the strength of welds can be maximised by favourable moulding conditions such as sufficiently high melt temperature, high tool temperature, heated metal inserts and fast injection times. Similarly to other plastics, more attention should be paid to filled or reinforced grades of PP. 

Alternatively, (part of) the poor quality materials may have to be removed prior to filling. 

UNSCOM verified that the principal CW agents produced by Iraq were sulfur mustard and the organophosphorus nerve agents cyclosarin, sarin, and tabun. The main CW issue that lacked resolution was the nature and extent of Iraq s program to produce VX. The Iraqi government claimed to UNSCOM that it had never filled weapons with VX but had merely produced limited, pilot plant-scale quantities of the nerve agent, totaling two to three tons of poor-quality material. UNSCOM disputed this claim. In late 1998, UNSCOM was forced to... 

The most difficult materials to study by NMR microscopy are those with short T2 or T2 relaxation times and/or with low concentrations of the nudear spins, which normally result in poor NMR signal intensities. One possibility for improving the image quality is to adapt the shape and size of the rf coils to the size of the objects in order to achieve the best possible filling factor and therefore the best sensitivity [1]. In addition, methods with short echo or detection times have been developed, such... 

The quality of a compressed tablet is determined by material fill characteristics and compression behavior. During compression, the rate at which tablets can be produced can be limited due to non-uniform material fill characteristics. Pending successful and reproducible material fill (die fill), the powder mass must form a coherent compact that stays intact upon ejection out of the die. Therefore, tablet press performance can be limited due to poor fill characteristics and/or poor compression behavior. 

In principle, the time-temperature superposition principle applies only to materials that are said thermo-rheologically simple and therefore its use with filled rubber compounds should give poor results. As seen in Fig. 10, this is not the case and, in the author s experience, it is common observation that good mastercurves are obtained with many complex polymer materials through time-temperature superposition, providing experimental data are of quality. In this respect, closed-cavity rheometers offer obvious advantages over open-gap instruments. 

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