Akademik Veri Yönetim Sistemi
Transportation Geotechnics, cilt.62, 2026 (SCI-Expanded, Scopus)
This study investigates the quality and performance variability of thirty two Deep Soil Mixing (DSM) columns constructed at two transportation infrastructure sites characterized by problematic soils: one dominated by peat and the other by high plasticity clay. Field applications were carried out using different cement dosages and construction parameters, including varying Blade Rotation Number (BRN). Quality control was performed through a comprehensive program comprising wet grab sampling, full length coring, laboratory index and strength testing, and pressuremeter measurements. The field results showed that achieving uniform improvement in these soils is inherently challenging. In peat deposits, extremely high void ratios likely prevented the formation of a continuous soil cement matrix, while in high plasticity clays, adhesion of cohesive soil masses to the mixing blades reduced mixing efficiency and resulted in localized zones of incomplete improvement along the column depth. Wet grab samples were found to systematically overestimate compressive strength due to sampling bias toward grout rich material. Detailed depth resolved core observations and pressuremeter measurements revealed pronounced vertical heterogeneity and structural discontinuities, even in columns constructed using identical parameters. Improvement levels were classified into six categories, demonstrating the coexistence of weak and grout dominated zones within the same column. Based on these observations, this study proposes a detailed depth resolved quality assessment methodology, termed the Discontinuity Informed Assessment Framework (DIAF), in which strength, material distribution, and vertical continuity are evaluated together. A continuity based indicator, Column Mixing Index (CMI), is introduced to quantify the degree of vertical continuity within DSM columns and to distinguish between marginally acceptable and well performing columns in the field. Within this framework, a three zone strength acceptance logic is also introduced that distinguishes between understrength, acceptable, and “questioned/overstrength” DSM materials, recognizing that both insufficiently mixed zones and excessively grout dominated zones may indicate construction related deficiencies and may influence field performance. A decision criteria table for DSM column acceptance based on CMI and strength distribution in DIAF was also proposed. The proposed approach includes continuity and material distribution into DSM quality evaluation in a quantitative manner, providing a more realistic and performance based basis for the assessment of DSM columns constructed in problematic soils.