Assignment 2 - Site Investigation And Pavement Design Assignment

Assignment 2 - Site Investigation And Pavement Design Assignment Assignment 2 - Site Investigation And Pavement Design â€" Assignment Example > TITLE: SITE INVESTIGATION AND PAVEMENT DESIGNLECTURE: xxx ©2016ObjectivesTo determine the importance of field investigation in a road projectTo determine a subgrade design CBRTo select a design traffic loadTo propose a Thin Sealed pavement designTo propose a basic construction methodologyIntroductionBefore an engineer can embark on any project, it is paramount that he understands the arrangement and properties (physical, mechanical and chemical) of the materials under the proposed construction site with reasonable accuracy and currency. This understanding is crucial since the durability and functionality of any engineering project, both structural and roads, relies heavily on the conditions of the underlying foundation and the ability of the structure to adapt to any changes that might occur in those conditions. Site investigation (otherwise referred to as field investigation) is conducted in a bid to allow for the assessment of the ground conditions (geo-environmental and geotech nical) and the environmental and engineering considerations that need to be analyzed with regard to the proposed development. In the case of roads projects, field investigation is very important given that the project spans across different kinds of underlying soil strata, unlike structural projects, which tend to occur on a single type of sol structure. Therefore, different road design is required for each section to accommodate these changes in soil strata. In road projects, this site investigation is done at periodic intervals so that the construction team is well aware of the conditions they are dealing with. The main information acquired from a site investigation is; The sequence and nature of the soil and rock strata (layers)The hydrological conditions at the site(ground and surface water conditions)The physical, chemical and mechanical properties of the soils and rocks found under the proposed constructionThe extent of the site investigation for a road project is often limit ed to the actual area where the road will be constructed. However, in some cases, the team will be required to carry out tests over the full road reserve width to determine if the adjacent materials could have any adverse effect in the foundation of the road, or the road structure itself. The depth of the field investigation is limited by the depth to which the effects of the construction of the road will be felt by the underlying strata, or until an incompressible stratum is reached, usually the base rock layer. This layer can support the loads subjected to the road structure by vehicle passing over it without any adverse effects. One of the tests used to carry out this field investigation is known as the California Bearing Ratio (CBR) test, which looks to determine the bearing pressure that the underlying soils strata can support. This report focusses on the CBR test. CBR Test DescriptionThe California Bearing Ratio (CBR) is a penetration test used to evaluate the mechanical str ength (load bearing strength) of existing natural ground, pavement subgrades and base courses under constructions in new carriageways. The California Department of Transportation developed the test, thus the name. The pressure (load) required to penetrate the substrate under consideration is measured. This pressure is applied using a plunger of standard area. The measured pressure is then compared to the load required to penetrate standard crushed rock material to the same level (13.2 kN and 19.8 kN for 2.5mm and 5mm penetration respectively). The two load values are divided to give the CBR value.