## 1 Introduction  
Earthquakes frequently cause disasters worldwide. Located at the boundary between the Philippine Sea Plate and the Eurasian Plate, Taiwan experiences earthquakes frequently. Disasters such as building tilting and soil subsidence are therefore common. A primary cause of these disasters is soil liquefaction. Although many studies have explored liquefaction, few have accounted for water pressure generation characteristics, which serve as key indicators of liquefaction, plastic index (PI) values, and mathematical models. Studies have obtained inconsistent results regarding the effect of fines content (FC) on liquefaction. Because the properties of fines in silt and clay soils differ drastically, the present study added fines with different PI values to soils to understand their effect on the liquefaction resistance and pore water pressure (PWP) excitation of soils under cyclic loading. [PERSON] et al. [1, 2] demonstrated that, in soil structure (fabric), fines may significantly influence relevant dynamic and static properties. [PERSON] et al. and [PERSON] and [PERSON] [3, 4] reported that, among field soils with the same N values obtained from the standard penetration test, those containing a higher FC exhibit greater resistance to liquefaction. [PERSON] et al. [5] used a centrifuge to measure the liquefaction, subsidence, and PWP of saturated clean Ottawa sand, focusing on partially drained conditions rather than undrained conditions and pore pressure dissipation. Some researchers have reported that when the FC of soil increases, the liquefaction resistance decreases. According to [PERSON] et al. [6; 7], the liquefaction resistance of a mixture can increase or decrease as the FC of the mixture increases in the laboratory. Fines in soils can be divided into three categories: non-plastic fines, low-plasticity fines, and high-plasticity fines. Non-plastic and low-plasticity fines have been widely studied [8; 9; 10; 11]. [PERSON] et al. [12] studied the effect of the grading characteristics of the liquefaction resistance of sand-silt mixtures in laboratory conditions. Regarding laboratory research, some papers [13; 14; 15; 16; 17] have investigated PWP in the liquefaction process by using different models and equipment. [PERSON] et al. [18] conducted a series of monotonic and cyclic triaxial tests and resonant column tests to assess the packing configuration of coarse and fine particles in terms of the equivalent intergranular void ratio. [PERSON] et al. and [PERSON] and [PERSON] [6; 7; 19] performed extensive experiments to study the behavior of sand-silt mixtures under cyclic loading. [PERSON] et al. [20] performed cyclic ring-shear tests on samples and reported that, when excess PWP (Ru) comprised 0.6-0.7 and the shear strain (\(\gamma\)) was 4-7%, Ru quickly reached 0.8 as \(\gamma\) continued to increase. [PERSON] and [PERSON] [21] investigated the dynamic properties of clay soil and gravelly soil in an earthfill dam. [PERSON] et al. [22] analyzed the effect of preloading on liquefaction resistance by analyzing variables such as FCs, prestress ratios, densities, and vertical stresses. [PERSON] et al. [23] estimated shear resistance during the liquefaction of a mixture of clay soil and sandy soil and discovered that the addition of bentonite decreased the resistance the most. This finding may explain the occurrence of natural landslides. [PERSON] et al. [24] and [PERSON] et al. [25] inspected the behavior and strength of clay soils both under cyclic loading and during earthquakes. [PERSON] et al. [26] examined riverside soils, and their results indicated that the liquefaction resistance of the soil specimens with a PI of 34% and non-plastic specimens were the highest and lowest, respectively, and that the liquefaction resistances of the undisturbed specimens were stronger than that of the reconstituted specimens. [PERSON] et al. [27] collected samples of sandy soil near the Pivain River in Bangladesh and subjected mixtures with different contents of non-plastic silt to cyclic triaxial tests.