Effects of cyclic loading on the undrained strength and stiffness of low plasticity clayey soils

Earthquakes, traffic and waves are the main actions that generate cyclic loads on the ground. Cyclic loading induces the development of pore pressures, which sometimes leads to problems of reduced strength and loss of soil stiffness.
The expansion of cities and industry means that there is an increasing need to build infrastructure on clay soils. In this sense, it is important to have a solid understanding of the mechanical behavior of soils under static and cyclic loads, especially in countries with high seismicity such as Peru.

In this research, an experimental laboratory program is developed, mainly through cyclic triaxial tests with high-precision instrumentation ('bender elements' and local instrumentation) to measure the evolution of soil stiffness and resistance during long-term cyclic actions. The results of the research will provide an experimental database for the design of infrastructures on low-plastic clays, such as those identified in Callao.

In recent years, different infrastructure projects have been carried out in Callao, among which Line 2 of the Lima Metro, Extensions of the Port Terminal, the Costa Verde del Callao road and the stabilization of the cliffs stand out. In all cases, geotechnical designs under earthquake or cyclic load conditions have been carried out from empirical relationships based on indirect soil tests, typically geophysical tests and static tests. The main reason for this is the lack of specialized equipment in cyclic tests in Peru, which allows establishing dynamic parameters of the soil. For this reason, a deficiency is observed in the studies and understanding of the seismic behavior of soils and their interaction with different structures. This being a very important factor for the engineering design that allows to ensure the correct functioning of the structures and safeguard the life of the population during seismic events.