A Portable Bender Element-Double Cone Penetration Testing Equipment for Measuring Stiffness and Shear Strength of In-Situ Soft Soil Deposits

• Published in: KSCE journal of civil engineering 2020, 24(12), , pp.3546-3560
• Main Authors: Kang, Xin, Sun, He-Mei, Luo, Hong, Dai, Tian, Chen, Ren-Peng
• Format: Article
• Language: English
• Subjects: Bend tests; Bender elements; Bending machines; Beryllium; Civil Engineering; Cone penetration tests; Dolomite; Dolostone; Engineering; Geotechnical Engineering; Geotechnical Engineering & Applied Earth Sciences; Industrial Pollution Prevention; Kaolinite; Laboratory experimentation; Measuring instruments; Penetration depth; Portable equipment; Prototypes; Sand; Shear strength; Shear wave velocities; Soft clay; Soil; Soil strength; Soils; Stiffness; Test equipment; Transducers; Velocity; Wave velocity; 토목공학
• ISSN: 1226-7988; 1976-3808
• DOI: 10.1007/s12205-020-1696-4

A portable bender element-double cone penetration (BE-DCP) testing equipment, which is invented as a prototype model for measuring the small-strain stiffness (shear wave velocity, V s ) and shear strength of in-situ soft soil deposits (loose sand and soft clay) is developed in this study. The shear wave velocity in two orthogonal directions ( V s-hv and V s-hh ) of the in-situ soils is measured from paired bender elements (BE) installed on the side of the cone shaft. The bender elements are housed in a mechanically controlled sliding block in the shaft which not only protects bender elements while the BE-DCP apparatus is being pushed into the ground, but also ensures a good contact between adjacent soil particles and benders when the target depth is reached. The real-time relationship of the pushing force and penetration depth is recorded by force transducer and laser displacement sensor and graphed in LabVIEW. Based on the cone penetration testing (CPT) theory, two formulas are derived to calculate the shear strength parameters of the in-situ soils. Test results obtained from both the portable bender element-double cone penetration (BE-DCP) testing apparatus and conventional laboratory experiments on Ottawa sand 20/30, four different sizes of Dolomite sands in various packing densities and Kaolinite under different water contents and densities as well as a field testing were compared and validated, indicating that the novel designed portable bender elementdouble cone penetration (BE-DCP) apparatus is robust, fast, and cost-efficient for measurement of small-strain stiffness and shear strength of in-situ soils.