Original Research Article: full paper (2023), «EUREKA: Physics and Engineering» Number 2 174 Engineering CRITICAL STRESS EVALUATION OF RIGID PAVEMENT DUE TO THE PRESENCE OF WATER IN EXPANSIVE SOIL SUBGRADE Wibowo Wibowo* Department of Civil Engineering 1 wibowo68@staff.uns.ac.id Ary Setyawan Department of Civil Engineering 1 Yusep Muslih Purwana Department of Civil Engineering 1 Bambang Setiawan Department of Civil Engineering 1 1 University of Sebelas Maret 36a Jl. Ir. Sutami, Surakarta, Indonesia, 575125 *Corresponding author Abstract The use of various types of rigid pavement is widespread because of its superiority in resisting heavy load vehicles. However, traffic loading complexity and subgrade response cause uncertainty during the design process. The presence of water in expansive soil issue swelling affected the flexural behavior of a rigid pavement slab. Rigid pavement relies heavily on the support and stability of the subgrade. Plain concrete is very weak in resisting tensile stresses so that the failure of rigid pavement slab structures often occurs in the expansive subgrade zone. Therefore, this study aims to numerically analyze the relationship between variations in the thickness of rigid pavement slabs on the flexural behavior parameters, such as critical and tensile stresses that affected water in expansive soil. The concrete’s performance limit was determined, using its material’s constitutive equation curve, and the data were analyzed using the finite element method. The results showed that the presence of water in expansive soil caused a change in soil volume (swelling), a reduction in soil bearing capacity (shrinking), and consequently, a rigid pavement cracked due to water variations in the subgrade. Generally, increasing the thickness of rigid pavement is a common method for mitigating the detrimental effects of expansive soil swelling. It is possible to provide reinforcement in other forms, which provide an opportunity to improve the performance of the con- crete slab as a rigid pavement. For example, stabilization of expansive soil with materials capable of reducing its expansive power can be done but it requires large resources to realize it. Another method is to provide reinforcement to the rigid pavement slab structure, so that the rigid pavement slab is able to withstand traffic loads and also the expansion and shrinkage behavior of the expansive soil. Keywords: critical stresses, expansive soil, finite element, pavement, plain concrete, shrinking, slab, subgrade, swelling, tensile stress. DOI: 10.21303/2461-4262.2023.002810 1. Introduction Jointed plain concrete pavement (JPCP) is a widely used rigid design application. Further- more, it is a very practical construction system and has become the preferred method in cases where technical needs are not considered, such as subgrade, loading characteristics, and special performance capacity [1−4]. This type of pavement relies on concrete strength to withstand compressive stresses. Therefore, when planning the construction of the pavement, force distribution should be con- sidered, whereas the tensile stress should be minimized. The configuration of the pavement slab does not permit excessive variation in its geometry and cross-section; nonetheless, the thickness and horizontal plane dimensions are frequently altered. Several tests have been conducted using the scalar model to determine the bending behavior of a rigid pavement slab, which demonstrates