## 1 Introduction  
Natural particulate materials, such as sandy soil, are found everywhere and are essential to many engineering applications. Various fields, from civil engineering to materials science, require an understanding of the mechanical behaviour of particle-to-particle [1, 2] and their interactions with different surfaces [3, 4, 5, 6]. Understanding these materials is strongly reliant on particle morphology, which has a significant influence on the mechanical response of granular materials such as sand. The term 'particle morphology' is used to refer to particle shape, size, form, sphericity, or surface roughness. With regards to particle size, the soil size in descending order is boulder, cobles, pebbles, gravel, sand, silt, and clay. The scope of this paper will be limited to sand, which is a granular material composed of individual particles classified into three sizes: coarse, medium, and fine sand, as specified by the Australian standard [7]. While the particle shape has been a topic that has raised many questions in the literature, its implication on the behaviour of soil is a major area of study with constant research progression. The soil particle shape can be graded on three independent properties: form (sphericity: overall shape), roundness, and roughness, each of which has a different influence on the behaviour of the material [8]. With regards to the sphericity, the soil particles can be bulky, flaky, and needle shaped. Sand particles are considered bulky, and their shape is mostly set during formation. Researchers often use terms such as 'well-rounded', 'rounded','sub-rounded','subangular', 'angular', and'very angular' to describe the roundness of bulky particles. However, the sand's surface roughness can change significantly with mechanical and chemical weathering of rocks and minerals over geological time [9]. While sphericity and roundness are macro- and medium-scale particle measurements, particle surface texture is a microscale measurement [10]. With regards to granular sand, the particle shape, including sphericity, roundness, and roughness, affect the sand's stiffness, strength, minimum and maximum void ratio (e\({}_{\text{min}}\) and e\({}_{\text{max}}\)), critical state friction angle (\(\varphi\)\({}_{\text{c}}\)), dilatancy (\(\Downarrow\)), dilation, strain localisation, and the evolution of strength anisotropy [11]. Furthermore, particle shape can significantly influence the compressibility of granular structures. Experimental studies have found that particle roundness and sphericity (particle regularity) can affect both packing density and compressibility [2]. The shape of soil particles, including roundness, angularity, and surface roughness, plays a significant role in determining soil mechanical behaviour. Roundness impacts how particles interact, affecting soil mass packing and stiffness [12; 13; 14]. Angular particles, due to their enhanced interlocking, exhibit higher friction angles and shear strength [15]. [PERSON] [16] found that as sample convexity decreased, friction angle increased. This statement was supported by an experimental and numerical study by [PERSON] et al. [17], whose results showed that angular particles have more shear strength compared to rounded particles. Surface roughness influences soil stiffness [18] and wave propagation parameters [19]. Angularity affects the undrained response of fine sands, with more angular particles offering increased resistance to movement, thereby boosting soil strength [20; 21]. The work of researchers like [PERSON] et al. [22] in studying the impact of these properties on soil behaviour contributes to more accurate predictive models, directly informing engineering practices. Particle size has an important effect on the behaviour of individual particles and the packaging density. [PERSON] and [PERSON] [23] investigated the effect of particle size on shear strength characteristics.