Name: GABRIEL BALDANZA MANTOVANELLI
Type: MSc dissertation
Publication date: 05/09/2016
Advisor:
Name |
Role |
|---|---|
| PATRÍCIO JOSÉ MOREIRA PIRES | Advisor * |
Examining board:
| Name |
Role |
|---|---|
| PATRÍCIO JOSÉ MOREIRA PIRES | Advisor * |
Summary: We can say that erosion is old as the Earth itself, which originated from natural phenomena that act continuously in the Earth's crust, resulting from the modification process of the planet. However, human action breaks the natural harmony by inserting practices that destroy the balance of the conditions of this process, causing major damages to the economy and to the environment. In Brazil, erosion by water is the most important erosion process. We can list different examples of problems caused by erosion. The options are the loss of agricultural productivity due to the degradation of productive land, dam failures by overtopping with the formation of erosion gaps and the collapse of bridges due the scour. The necessity to know the erosional soil behavior is evident in several engineering areas, especially to the civil engineering and geotechnical engineering. The great majority of the guidelines established for the study of soil erosion were developed for coarse grained soils, particularly to sands and gravel, in which the absence of electrochemical forces allow the use of simplified mathematical models based on the weight of each soil particle. To achieve a general study about cohesive and non-cohesive soils, it is proposed an apparatus to fill this knowledge gap through the concept of erodibility. The erodibility of a material is defined as the erosion rate to which the material is subject when exposed to a flow. This study aims to evaluate experimentally through the developed apparatus the erosive behavior of a soil and its respective shear strength for different flow velocities. Also, this work seeks to identify the critical velocity of the material and his respective critical shear stress responsible for the sediment motion. The studied soil was classified using the unified system of soil classification (SUCS) as clayey sand (SC) from the city of Serra - ES (sedimentary soil), with a percentage of clay and silts equal to 44.9% ± 1.3%. Through the result of the tests, this paperwork used the erosion classification of soil through the erosion rate and the flow velocity as proposed on the circular HEC-18 (2012) of the Federal Highway Administration (FHWA-USA) which relates the erodibility with the SUCS classification in terms of soil's mean diameter. It was noted that the average erosional time observed was reduced to its half for velocity increments of 0.5 m/s. Hence, the erosion rate approximately doubles for the same velocity increments. It was also noted that moreasing soil fines content can influence the soil behavior, decreasing the erosion rates.
Keywords:
Erodibility; overtopping of dams; erosion rate, piston-type device.
