Forensic Study on Federal Road Pavement Failures at Rengit and Semerah, Batu Pahat

Forensic investigations in engineering term may be conducted to identify the causes of failure to facilitate the design of proper repairs, or to improve the performance or lifespan of a component, assembly, or structure. This paper presents the combination of geotechnical investigation and geophysical survey method as a forensic tool to predict the causes of pavement failure occurred along the coastal area of federal road FT005. The number and type of field testing are varying on each selected study area at Rengit and Semerah, Batu Pahat as this location constructed on soft soil area. Non-destructive testing (NDT) method using electrical resistivity tomography (ERT) were chosen to be applied at the worst severity of the road failure. Three number of resistivity lines of 100m and 200m were laid out using ABEM Terrameter LS2 with gradient method of electrode arrays covering up to 40-meters depth. Then, further testing of destructive testing (DT) method using borehole drilling conducted near the ERT lines to obtain soil profile with SPT N-value measurement. The disturbed and undisturbed samples were obtained to carried out laboratory test for soil classification. After that, inspection of road pavement layers were implemented at five number of trial pit tests which excavated up to subgrade layer to determine the thickness of the materials used in road construction. Three number of mackintosh probe test were also conducted on top of the subgrade layer after the trenching to obtain the strength of the subgrade layer. The results presented showed that severe longitudinal cracking were the predominant premature failures on the roads studied due to settlement effect of soft soil. The analysis obtained from RES2DINV program stated that the subsurface profiling was dominantly in saturated condition which the resistivity value was less than 100 ohm.m. From the SPT N-value it is observed that, the very soft soil layer is up to 8 m followed by the soft to stiff clays soil. Another cause of failure was resulted from the differential settlement due to the effect of different design of road construction with varies material used. The reliability and efficiency of the instruments used were also discussed in this study.

Estimation of Pressuremeter Modulus and Limit Pressure in Weathered Granite Based on the SPT-N Value and Chemical Weathering Index: A Case Study in South Korea

A pressuremeter test (PMT) is a representative and highly reliable in situ test for assessing the stress–strain behavior of weathered granite. Its application, however, is restricted by its cost and time requirements. Many researchers have also investigated the correlations between the SPT-N value and the pressuremeter modulus (Em) and limit pressure (PL) of soils, but they have mostly focused on sand, silt, and clay and have employed simple regression analysis. In this study, equations for Em and PL were derived for weathered granite through multiple nonlinear regression analyses using a chemical weathering index that quantitatively represents the degree of weathering. Nonlinear multiple regression analyses were conducted by combining the allometric models that produced the optimal correlations between Em, PL, energy corrected SPT-N (SPT-N60), and normalized VR (Vogt’ ratio) with vertical effective stress. The obtained equations for Em and PL had higher R2 values (0.76 and 0.46, respectively) compared with the simple regression equations reported in previous studies. Because local characteristics are important determinants of the engineering properties of geo-materials, the Em and PL equations proposed in this paper are intended for use in geotechnical surveys of weathered granite in South Korea.

Correlation of Electrical Resistivity and SPT-N Value from Standard Penetration Test (SPT) of Sandy Soil

In general practice, soil investigation (SI) incorporating bore hole sampling produced the most reliable value of the relevant soil parameters for the purpose of actual calculation on factor of safety (FOS) in slopes even tough time consuming and very expensive. Assessments of slope stability using electrical parameters have least been research by many scholars due to non-destructive and very sensitive and it is attractive tool for describing the subsurface properties of the slope without disturbing the physical characteristic of the soil. The method has been applied in various contexts like groundwater exploration, agronomical management by identifying areas of excessive or soil horizon thickness and bedrock depth. This paper investigates the relationship between electrical resistivity and SPT-N values of sandy soils. The research work consists of field resistivity surveys, soil boring and soil characterization tests. Field survey included 1D vertical electrical sounding (VES) and SPT method in obtaining SPT-N value. The test being conducted on 3 different areas and 11 sandy soil sample with electrical, physical soil characterization data which being used for least-squares regression method. In this part of the study, correlations of electrical resistivity with SPT values of soil were assessed. The findings showed good correlation between the resistivity and soil properties. The obtained results demonstrate the possibility usage of electrical resistivity survey as an alternative to standard penetration test SPT is possible.