*Corresponding author: 1 hf110217@siswa.uthm.edu.my 2 adnanz@uthm.edu.my 3nursyahidah.saedon@yahoo.com An overview on the Cyclic Loading Behaviour of Peat Soil Siti Nurul Aini Zolkefle 1 , Adnan Zainorabidin 2 , Nursyahidah Saedon 3 1 Student, Civil and Environmental Engineering Department, University of Tun Hussein Onn Malaysia, Johor 2 Lecturer, Civil and Environmental Engineering Department, University of Tun Hussein Onn Malaysia, Johor 3 Student, Civil and Environmental Engineering Department, University of Tun Hussein Onn Malaysia, Johor 1. Preamble Recently, the reactions towards dynamic or cyclic loading has been of fear and concern to engineers mainly geotechnical and geophysicists for years. Most research has been devoted to the dynamic response of inorganic soils such as sand, clay, silt and gravel with significant organic content. However, there were increasing interests in dynamic response of highly organic deposits such as peat have been developed [1]. O‟Reilly and Brown [2] described the term „dynamic‟ as a system of loading which depicts a degree of regularity both in its magnitude and in its frequency, whereby the word „cyclic‟ comes out to be something of a misnomer and usually used by engineers to explain non- static repetitive soil loading. On the other hand, Yang and Sze [3] defined „cyclic‟ or „dynamic‟ as the symmetrical loading which constitutes level ground conditions in the free field, where no initial static shear stresses act on the horizontal planes of the elements of soil. The researchers developed the simulation of cyclic loading condition in a laboratory with the condition of symmetrical loading, non-symmetrical loading with stress reversal and non- symmetrical loading without stress reversal. Jarret [4] described „peat‟ as a soft soil in an engineering concept and very compressible in terms of strength. This soil has long been recognized by geotechnical engineers as a problematic soil and is noted for its very low unit weight, very low shear strength, very high compressibility and rate-dependent behaviour [1]. Fig. 1 shows an example of road settlement caused by dynamic loading at Cerrigydrudion, North Wales. This road indicates some patches along the settlement that was eventually constituted towards the dynamic effects. Fig. 1 : Road settlement at Cerrigydrudion, North Wales. [5] Basically, engineers normally define static and dynamic problems concerning to the analysis and design of foundations. These types of problems may depend on the natural source which produces it [6]. Saran, [7] had compiled the features of static and dynamic loading towards soil and explain in detail the characteristics as shown in Table 1. Abstract: Recently, the reactions towards dynamic or cyclic loading has been of fear and concern to engineers mainly geotechnical and geophysicists for years. The significant parameters in Geotechnical Engineering which control the effect and reaction of soil towards the dynamic loading are shear modulus and damping ratio. Most of researchers conducted investigation on the dynamic loading of soft soils such as sand and clay but only a few had discovered the behaviour of peat in terms of static and dynamic loadings by using Cyclic Triaxial and Torsional Shear or Resonant Column tests. Hence, this paper present a critically review on the earliest work on the dynamic loading onto peat soil associated with Kramer [1], Wehling et al [9], Kramer, [13], Boulanger et al. [14] and Kishida et al [15]. The analysis and conclusions describes the influence of effective confining pressures towards dynamic peat soil behaviour at different locations. After considering these factors, additional testing is strongly advice to precisely evaluate the properties of peat and to study the reasons of increasing effective confining pressures due to the size of sample, organic content and fiber content as well as the percentage of vegetative in the sample. Keywords: Cyclic loading, Peat soil, confining pressure.