Abstract
Soil dilatancy and partial drainage have great influence on the consolidation coefficient assessment of silty soils with clay content of less than 30% in the Yellow River Delta using the CPTu. This paper discussed the effect of soil dilatancy and partial drainage on the pore pressure response and dissipation of piezocone test in shallow silty soil of the Yellow River Delta through variable penetration rate tests in a pressure chamber and a series of supplementary soil element tests. The results show that the pore pressure dissipation curve is affected by soil type and degree of consolidation. The soil dilatancy is the key factor affecting consolidation coefficient inversion of shallow silt and silty clays. The initial pore pressure is negative and the pore pressure increases to umax first, but the umax value is very small in the Yellow River Delta silt. The inversion method used for shear contractile soil cannot be used to invert the mechanical properties of shallow silty soil directly, and a new consolidation curve normalization method is proposed. This paper provides a reference for the consolidation coefficient inversion of CPTu data in the Yellow River Delta area.
Highlights
As there are a lot of oil and gas transmission pipelines in the Yellow River Delta [1,2,3], the evaluation of soil consolidation parameters is of great significance to the evaluation of settlement caused by human activities
DeJong and Randolph [15] discussed the influence of partial drainage on soil classification results; Randolph and Hope [16] discussed the influence of penetration rate on test results by centrifuge; Silva et al [17], Yi et al [18], and Mahmoodzadeh et al [19] discussed the influence of partial drainage on test results by numerical method
The influence of partial drainage is eliminated, The steps of this method can be summarized as follows: (1) obtain Δumax; (2) treat the dissipation curve as a U(which is Δut/Δumax)-t curve, mainly for the convenience of obtaining the position of T50; (3) in the U(which is Δut/Δumax)-t curve, obtain the value of Δuextrap/Δumax by the tangent line; and (4) using Δuextrap to obtain the U(which is Δut/Δuextrap)-t of 14 curve, obtain t corresponding to 40% dissipation, and T40 = 0.38 in silty clay with12clay content of 30% and T40 = 1.3 in silty clay with clay content of 20%, using Formula (3) to obtain the horizontal consolidation coefficient ch
Summary
As there are a lot of oil and gas transmission pipelines in the Yellow River Delta [1,2,3], the evaluation of soil consolidation parameters is of great significance to the evaluation of settlement caused by human activities. The cone penetration test (CPTu) is one of the most widely used geotechnical in situ testing methods. It is a fast, reliable, and economical means for obtaining soil properties [4,5]. As the consolidation coefficient cv of silts is larger than that of clay, partial drainage would usually affect CPTu test data at the standard penetration rate in silts, and the interaction between the structure and soil is affected by partial drainage [12,13,14].
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