**2. Fracture mechanics**

Fracture mechanics is a new field that integrates fracture mechanics with the study of mechanical characteristics [7]. Mechanical properties study and fracture mechanics have recently been combined to form the emerging topic of fracture mechanics. Quantifying the connection between material qualities, stress, crack length, and crack propagation mechanisms is the goal of fracture mechanics [8]. The study of fractures and other phenomena associated with breaking is the focus of fracture mechanics. The advancement of fracture mechanics is inextricably tied to certain recent, high-profile disasters. It all started during World War II, when hundreds of ships bringing citizens to safety on the high seas were heavily damaged, the reason for the same being unknown at that time. During World War II, the construction of Liberty ships transitioned from riveted to welded construction. However, this change resulted in numerous failures caused by subpar weld quality, stress concentrations, and the use of brittle materials. As a result, approximately 400 of the 2700 Liberty ships constructed during the war were severely damaged due to these factors. The investigation of these failures kickstarted a new area of study called "fracture mechanics", which aimed to understand the behavior of materials under stress and the mechanisms that lead to failure. The study of fracture mechanics has since become an important tool for identifying weaknesses and predicting the failure of materials in various applications, including soil strength identification. The Comet occurrences in 1954 led a thorough investigation into the causes, which greatly improved our understanding of fracture and fatigue. In July of 1962, the Kings Bridge in Melbourne suddenly collapsed after a car weighing 45 tons crossed one of the spans. Four girders failed because a crack extended from the bottom to the top of the girder, through the web and in some places the upper flange as well. Although no one was injured, the incident sparked a thorough investigation into the cause of the failure, which ultimately led to significant improvements in bridge safety and engineering practices. This kind of events become prelude for the initiation of Fracture mechanics study which progressed well and helped to avoid many disasters.

There are mainly two primary kinds of fracture mechanics approach: linear elastic fracture mechanics (LEFM) and elasto-plastic fracture mechanics (EPFM) (EPFM). LEFM excels at handling brittle-elastic materials such as high-strength steel, glass, ice, concrete, etc. In contrast, ductile materials, such as low-carbon steel, stainless steel, some aluminum alloys, and polymers, always exhibit plasticity before fracture. Linear fracture mechanics is still a good approximation to reality, but only for loads below a certain threshold. Hence it is evident that understanding the fracture properties of a material is necessary to produce a good quality product. In recent years, fracture mechanics has increasingly been applied in civil engineering to understand the properties and behavior of different materials. For example, stabilized soil and engineered soil are materials that have been extensively studied using fracture mechanics to analyze their cracking patterns and failure modes, among other factors.

#### **2.1 Fracture mechanics approach towards soil strength**

Soil always has some kind of defect, such as an inclusion, a vacuum, or a crack in any form. Environmental stress or mechanical strain could cause cracks to spread from these defects. Multi-layer pavement systems, buried pipes, and embankment dams use soil for sub-grade layers. Failure and fracture of this material can deform buildings and affect their long-term performance. Tensile type fracture (mode I fracture) of soil materials has been tested using several ways. Real-world loads can cause mixed mode tensile-shear deformations in clay materials. Among the failure pattern in soil, desiccation cracking [9–11] in cohesive soil, where cracks form due to volume changes with removal of water, has received a lot of attention from the scientific community. However, crack formation in the core of dams, the wall of tailings, and the liners of landfills, where the soil is saturated above the shrinkage limit, has received much less attention. Significant economic, environmental, and human losses have resulted from the collapse of these structures [12]. Over the course of the past three decades, linear elastic fracture mechanics (LEFM) has solidified its place as a key discipline within geotechnical engineering [13] Numerous geotechnical engineering literatures document the use of LEFM with great success in actual engineering projects. Because it is not possible to verify that failure criteria based on yield dominating failure of material, such as Tresca, Mises, or Coulomb, can be used to analyze the failure of brittle materials induced by fracture [14, 15] established that LEFM is a useful method for studying the fracture dominated failure or rupture of a wide variety of geomaterials, including stiff and over-consolidated soils, in particular those having cracks [16].

Correct knowledge of shear strength of the soil is necessary for the design of traditional geotechnical constructions including foundations, slopes, and retaining walls. But the void ratio, composition, friction angle, cohesion, stress history, temperature, strain, strain rate, and structure all have an impact on the shear strength of soil. When the tension exceeds the soil's bearing capacity, failure is expected [17, 18]. Owing to these factors influence, analyzing soil failure become cumbersome. When there are no fractures present, a brittle failure that happens quickly and is guided by linear elastic fracture mechanics (LEFM) [19, 20]. When it comes to design, traditional soil mechanics criteria like cohesive strength (c) and angle of internal shearing resistance (phi) fall short. If one want to prevent failure in brittle and quasi-brittle materials by employing LEFM, you need to pay attention to the parameters, especially the critical stress intensity factor KIC [18, 21–24]. At low saturation, cohesive soil starts to operate like a quasi-brittle material, failing mostly in ways described by linear elastic fracture mechanics. In the field of fracture mechanics, the KIC is a crucial mechanical characteristic that indicates a material's resistance to fracture failure under mode I stress circumstances. Numerous studies have focused on the best way to calculate KIC and how it relates to other mechanical parameters like tensile strength t in geomaterials. Soil fracture toughness, defined as its resistance to crack initiation and propagation, is an important quality for determining the safe design limits of critical infrastructure including pipelines, bridges, and dams [25, 26]. Hence, it is found that fracture mechanics-based study on soil will help designers and engineers to develop better engineering soil [27]. In this work, we have tried to understand the real research works being undertaken in this domain.

Thus, research progress analysis is necessary to comprehend the research being done by different researchers and guide future research directions. This paper proposes quantitative visual representation and systematic analysis of existing studies

#### *Fracture Mechanics Application in Soil Strength Identification: A Scientometric Analysis DOI: http://dx.doi.org/10.5772/intechopen.112451*

to meet the requirements and provides a comprehensive and up-to-date review of fracture mechanics approach to engineered soil design. The scientometric analysis used here provides (a) a better understanding of the domain of knowledge encircling fracture mechanics approach towards engineered soil design, (b) more objectivity than prior reviews, and (c) a quantitative representation of the domain.

This study focuses on answering the following RQs:


This paper took a scientometric approach to answer the above-mentioned questions using most widely used bilbiometrics software for analysis. Scientometrics is widely used by many researchers to understand the research landscape and it can provide information related to important keywords, authors, affiliations, countries involved in research, organizations funding the research and other important information that can serve as a guideline for new researchers.
