Dynamic Load Plate workshop (LWD)
On September 4, an activity aimed at professionals and technicians linked to the use, implementation and interpretation of test results of dynamic loading plate was made Light Weight Deflectometer ZORN. The workshop was taught by the teacher MSc. Ing. Leonardo Abreu and engineers involved several construction companies in the industry and the ministry.
The LWD easily allows for in-situ elastic modules natural soil and compacted. Its principle is to apply a dynamic load on the soil surface and measure the deflection occurring during the impact. An accelerometer records the acceleration suffers plate and allows, from a double integration to estimate the vertical deformation. It is important to recognize this fact: obtaining dynamic modulus It is a mathematical operation and no direct measurement. The results obtained are: displacement vs. time diagrams, degree of compatibility, maximum displacement at each impact and dynamic modulus Evd.
The in-situ elastic modulus, evaluated by LWD parameters correlated with structural capacity (CBR, MR), degrees of compaction and Ev2 (second branch loading static load test Circular plate) modules.
One of the points discussed in the workshop is the fact that different equipment there have similar operating mechanisms, but differ in their mode of operation (deformation measured on a plate versus extent the soil surface) causing difference in responses. The different configurations for the same LWD produce different results soil deformation and elastic moduli, and the differences are very difficult to predict.
Asimismo, uno de los puntos de controversia planteados es la utilidad del ensayo para determinar la disminución del módulo de las bases estabilizadas con cemento luego de la microfisuración. En estos casos, la rigidez de estas capas es tan alta que la profundidad de influencia de los golpes dinámicos disminuye radicalmente. Se deberá estudiar a fondo si es necesario aumentar el peso o disminuir el área de la placa.
Por último, se procedió a comparar el equipo ZORN adquirido hace tres años por el CITEVI, con uno nuevo, mostrando similitudes en los resultados. Esto demuestra que el equipo es robusto y confiable, y que la falta de repetitibilidad que se le adjudica debe ser compensado con el aumento de los registros (para conseguir un 95 % de confiabilidad es necesario realizar un mínimo de 50 mediciones, con una separación máxima de 10 m entre ellas).
The immediate results positions the LWD as a powerful tool control work to assess the degree of compaction of bases and to describe structural capacity (determined in-situ elastic modulus and correlate with the CBR). It was demonstrated the high interest of the participants in the issues raised and agreed to establish a diverse group to further discuss the strengths and weaknesses of these teams work.
