STUDI PENGARUH NILAI CBR DAN KEMIRINGAN TOPOGRAFI TERHADAP KETEBALAN LAPISAN JALAN Studi Kasus : Proyek jalan Tol IKN Seksi 5B STA 0+000 – STA 13+276

This study analyzes the influence of California Bearing Ratio (CBR) values and topographic slope on pavement thickness in the IKN Toll Road Project Section 5B, Penajam District, North Penajam Paser Regency, East Kalimantan. Laboratory tests showed CBR values ranging from 2.27% to 22.97%, with an average of 3.2%. Soils with low CBR (<6%) require subgrade improvement to increase bearing capacity, which affects pavement thickness. The study area’s topography is divided into five slope categories, from flat to very steep. Steep slopes (>25%) dominate, covering 59.14% of the total area. These conditions demand thicker pavement layers to maintain road stability. Data were collected using CBR testing equipment, slope measurement tools, and analyzed with GIS (ArcGIS) and Microsoft Excel to evaluate CBR and slope distribution. Results indicate that the combination of CBR and slope significantly affects pavement design. Structural planning must consider soil properties and topography to withstand traffic loads. Based on cumulative traffic load calculations (ESA5), flexible pavement with hot rolled sheet (HRS) and thick foundation layers is recommended, especially for steep areas. The proposed structure consists of a 30 mm HRS wearing course, 35 mm HRS base course, 250 mm upper foundation layer (LFA Class A), and 125 mm lower foundation layer (LFA Class B).This study contributes to durable and adaptive road design capable of handling increasing traffic demands.
Keywords: CBR, topographic slope, pavement thickness, IKN, road design