CONSOLIDATION STATE AND GEOLOGICAL ORIGIN ANALYSIS OF LIANYUNGANG MARINE SOFT SOIL

The consolidation state of soft soil is an important index to analyze its settlement and deformation. In order to study the consolidation state of Lianyungang marine soft soil, several sets of standard consolidation tests, field vane test(FVT) and settlement monitoring by metal-based cable-like cables were used. Due to the surface layer, the shallow and deep soft soils show different consolidation states, and there is a critical depth(5~6 m) in the consolidation state. The fitting curve of in-situ soil shear strength and buried depth shows that the apparent over-consolidation ratio(OCR₁) is greater than 1, but this includes the structural strength of the soil and cannot reflect the maximum effective stress, which the soil has experienced in the geological history. The average value of OCR₁ above the depth(5m) is 1.74, and the average value of OCR₁ below the critical depth is 1.01, both of which are slightly over-consolidated soils. Based on the standard consolidation test using the plastic sample test data, the OCR₂(over-consolidation ratio) of the soft soil calculated is less than 1 below the critical depth, which indicating that it is an under-consolidated soil, and the maximum effective stress suffered in the geological history is less than the current soil effective stress on the body. The OCR₁ value by the FVT test is greater than the OCR₁ by the standard consolidation test, which is related to the disturbance of the indoor test sample and the change of the soil stress state. The data by the indoor compression test will underestimate the OCR₁. Although OCR₁ is not a true over-consolidation ratio, this indicator is directly related to engineering construction, and it is necessary to make good use of the structural strength of the soil. Finally, the distribution law of soft soil settlement monitoring data by metal cable-like cable is consistent with the distribution law of soft soil OCR₁.