Proceedings of the World Congress on Civil, Structural, and Environmental Engineering (CSEE’16) Prague, Czech Republic – March 30 – 31, 2016 Paper No. ICGRE 114 DOI: 10.11159/icgre16.114 ICGRE 114-1 The Influence of a Laboratory Testing Method on the Index of Density of Sand Waldemar St. Szajna, Paulina Lechocka Institute of Building Engineering University of Zielona Gora Szafrana 1 Str., Zielona Gora, Poland W.Szajna@ib.uz.zgora.pl; Paulina.Lechocka@gmail.com Abstract - The paper presents the problem of evaluation of the index of density for sand by various laboratory methods. The parameter is well-suited for describing the state of coarse-grained soils (sand and gravel) because it is dimensionless and normalized. It takes values between 0÷1. The index of density may be defined by maximum, minimum and apparent dry density, values of which should be evaluated in laboratory tests. Because of its definition, the parameter is very sensitive to measurement errors of dry density values. Even inconsiderable values of errors affect significantly the index of density. To estimate this sensitivity, a series of tests was performed. The tested material was classified as sub-angular, even-grade, medium quartz sand. Its maximum dry density was determined with the use of: Tapping Fork, Vibrating Table, Vibrating Hammer, Standard Proctor and Modified Proctor methods. The minimum values of dry density were determined with the use of Funnel method (spout diameter 10 mm and 12.5 mm) and Inverting Cylinder – Kolbuszewski method. The total numbers of 35 maximum and 26 minimum dry density tests were performed. The tests results revealed significant differences in the values of the index of density evaluated by various standard methods. It may result in misunderstandings. Despite the same definition, values received by various national standard procedures differ so much that it is difficult to regard it as one parameter. The fact that engineers refer to this parameter with the same name, may lead to even greater confusion. The authors suggest that additional notation should be introduced in the symbol to clarify the methodology used. Keywords: relative density, dry density evaluation methods, laboratory classification tests, vibratory compacting methods, granular soil 1. Introduction The advancing international cooperation in technology means that national design standards and standards for material testing are adjusted to or even replaced with international standards. In Europe, it was the introduction of Eurocode 7 and related standards which significantly influenced the abovementioned process of modifying national standards in the field of geotechnics. As a result of these changes, engineers in various countries need to supplement their knowledge, but at the same time they may confront the existing soil testing procedures with the new methods. In geotechnical design, soil strength and stiffness are the key parameters. Not only do most of these parameters depend on the type (nature) of the material (i.e. mineralogical composition, shape of grains, particle size distribution, etc.), but also on its state and structure (fabric and bonding). The state of soil, understood as a granular porous medium, may be described by a number of various parameters, of which the most commonly used are: porosity ( n), void ratio (e), bulk density (), or dry density (d). However, the above state parameters are not always convenient in use. For example, if the void ratio of sand is 0.6, it is impossible to conclude whether it is in a loose or dense state. Moreover, for angular or poorly graded sand, this value will indicate its considerable density, whereas for well-rounded or well-graded sand it will suggests its loose state. The evaluation of the state of soil medium with the use of the above parameters (n, e, , or d) is possible if their extreme (minimum and maximum) values are known. A parameter which is well-suited for the determination of the state of coarse-grained soils (sand and gravel) is the index of density ) /( ) ( m in max max e e e e I D    . This is a dimensionless and normalized parameter, and it takes values between 0÷1. As seen in the above formula, the definition of this index includes the minimum, maximum and the current values of void ratio. The significance of this parameter in geotechnical engineering results from the fact that the effective angle of internal friction ’ correlates well with its value.