Category: Geotechnical Engineering

CIVIL ENGINEERS ARE IN THE MIDST of a construction revolution. Heavy structures are being located in areas formerly considered unsuitable from the standpoint of the supporting power of the underlying soils. Earth structures are contemplated that are of unprecedented height and size; soil systems must be offered to contain contaminants for time scales for which past experience is either inadequate or absent. Designs must be offered to defy the ravages of floods and earthquakes that so frequently visit major population centers.
All structures eventually transmit their loads into the ground. In some cases this may be accomplished only after circuitous transfers involving many component parts of a building; in other cases, such as highway pavements, contact is generally direct. Load transfer may be between soil and soil or, as in retaining walls, from soil through masonry to soil. Of fundamental importance is the response that can be expected due to the imposed loadings. It is within this framework that geotechnical engineering is defined as that phase of civil engineering that deals with the state of rest or motion of soil bodies under the action of force systems.

Category: Geotechnical Engineering Defining Terms Weight–Volume Problems

AASHTO classification system — A classification system developed by the American Association of State Highway and Transportation Officials that rates soils relative to their suitability for road embankments, subgrades, subbases, and basis. Atterberg limits — Water contents at which soil changes engineering behavior; the most important ones in classification are the liquid limit and plastic limit. Boulders — Rock particles larger than 9

View Article...

Category: Geotechnical Engineering Weight–Volume Problems Involving Only Relationships

If only relationships (e.g., void ratio or unit weight) are given, the quantity of soil is indefinite and only other relationships can be calculated. Nevertheless, it is convenient to solve such problems using a phase diagram and assuming one fixed weight or volume value. That quantity of solids, water, or soil is “brought to the paper” and used to calculate

View Article...

Category: Geotechnical Engineering Soil problems Weight, Mass, Volume

Example 15.4 Assume that a compaction mold having a volume of 1/30 ft3 was filled with moist soil. The total weight of the soil in the mold was found to be 4.10 lb. The soil was oven dried and its weight after drying was 3.53 lb. The specific gravity of solids was known to be 2.70. Water content, void ratio,

View Article...

Category: Geotechnical Engineering Weight–Volume Problems Involving Defined Quantities of soil

Weight-volume problems may be divided into two categories: those where there is a defined quantity of soil, and those where the quantity of soil is not defined and it is only desired to make conversions among relationships. The solution to problems of the first category is discussed first; discussion of the second category follows. Problems of the first category can be solved in

View Article...

Category: Geotechnical Engineering Conversion of Unit Weight and Density of soil

A soil sample has a total unit weight of 125 lb/ft3. It is desired to find its total unit weight in kN/m3 and its density in kg/m3. Although the problem can be worked using a chain of conversion factors, a simpler approach is to consider that the unit weight and density of the soil sample have a constant ratio to the unit weight

View Article...

Category: Geotechnical Engineering Specific Gravity of soil

To facilitate working problems across different sets of units, it is convenient to express the unit weight and density of solids as a ratio to the unit weight and density of water. This ratio is termed the specific gravity and denoted Gs. For most soil minerals Gs is commonly in the range 2.64 to 2.75. Note that:

View Article...

Category: Geotechnical Engineering Density of soil

The term density is used herein to denote the mass-to-volume ratio of a material. However, some references, particularly older ones, use the term to describe unit weight. Density is denoted by p. Because m = W/g, the unit weight terms defined above can be converted to mass densities as follows: In the SI system mass densities are commonly expressed in

View Article...

Category: Geotechnical Engineering Unit Weight of soil

The ratio of the weight of a material to its volume is its unit weight, sometimes termed specific weight or weight density. The unit weight of water, Yw, is 9.81 kN/m3 in the SI system and 62.4 lb/ft3 in the English system. The unit weight of solids, Y s, varies with the mineralogy of the soil particles but is commonly

View Article...