# Dynamic Properties of Sand-Sawdust Mixture for Modeling Deposit Soil
## 1 Introduction  
Seismic responses of the soil-structure interaction system are frequently demanded in engineering applications, particularly those involving large project construction. Due to the complexity of soil properties, the shaking table test is often used to investigate the seismic response of systems and to check the validity of the theory. The reliability of these model test results depends on the design of the dynamic similarity between the model system and the prototype system. To meet the requirement of similarity between the natural frequency of the original system and that of the test system, various materials are added to the soils used as the model soil for experiments. Materials may include iron powder or iron crystal sand [1, 2], synthetic fibers [3, 4, 5, 6], or rubber particles [7, 8, 9, 10]. However,iron powder and synthetic fibers are expensive, and the rubber particles may introduce environmental problems. Sawdust, a light-weight, inexpensive, and environmentally friendly material, is frequently used in practical engineering. Applications include its use as an additive in concrete or in amended lateritic clay as a landfill liner to retain heavy metals [11; 12; 13; 14; 15].  
Researchers have conducted many studies on the engineering properties of soils or of soil mixtures with various additives. The factors affecting the dynamic properties of engineering soil have also been widely studied. [PERSON] [16] studied standard sand and clay and indicated that the loading frequency had a significant influence on the dynamic properties of clay. [PERSON] [17] presented equations for the determination of the shear modulus, Young's modulus, and damping of sandy soils. [PERSON] et al. [18] and [PERSON] et al. [19] found that the dynamic shear modulus and damping ratio of soil were influenced by confining pressure, loading cycles, effective average principal stress, etc. [PERSON] et al. [20] and [PERSON] et al. [21; 22] found that the cyclic and dynamic loading history markedly affected the dynamic properties of saturated clay and dry sand. Similar to real soil in practical engineering applications, it is necessary to investigate the dynamic characteristics of the soil-sawdust mixture. [PERSON] et al. [23] and [PERSON] et al. [24] studied clay-sawdust mixtures, and indicated that the consolidation stress and confining pressure were very significant factors influencing the shear modulus of the mixture. [PERSON] et al. [25] also showed that the shear modulus of the sand-sawdust mixture was notably affected by the sawdust content. As the soil-sawdust mixture can easily obtain different shear wave velocities by changing the sawdust content in the soil mixture, it has been widely used in shaking table tests [26; 27; 28; 29; 30].  
Extensive testing for the dynamic properties of the sand-sawdust mixture have not been conducted, therefore, it is inadequately understood how the content ratio of the sand and sawdust, as well as the confining pressure affect the shear modulus and damping ratio. In this paper, a series of consolidated drained dynamic triaxial tests were carried out on sand-sawdust mixtures to investigate how the shear modulus and damping ratio varied with shear strain. The strain behavior of the mixture was captured with tests covering a range of strain amplitude from approximately \(10^{-4}\) to \(10^{-2}\) and a confining pressure for the triaxle test (\(\sigma_{3}\)) equal to 10 kPa, 20 kPa, 50 kPa, 100 kPa, 150 kPa, and 200 kPa. The samples were mixed with several different percentages of sawdust and sand. The variation of shear modulus and damping ratio with the percentage of sawdust and confining pressures are presented.