The characterization and analysis of the cementation properties of novel biopolymer binders in soils are essential for their potential application in geotechnical engineering. This study investigates the cementation effect of a novel zein biopolymer binder on sandy soils. Soil specimens are mixed with various contents of zein biopolymer ranging from 0 to 5%. The mechanical and microscopic characteristics of the treated specimens are evaluated using unconfined compression tests and scanning electron microscopy, respectively, after curing for 3, 7, and 28 days. The results show a consistent increase in compressive strength and elastic modulus of treated soils with increasing curing periods and biopolymer contents. A small amount (1%) of zein biopolymer increases soil strength and elasticity regardless of gradation. Additionally, the bonding force between the soil–zein biopolymer increases linearly with soil uniformity. Therefore, the application of zein biopolymer can be potentially used as a binder for fine- and coarse-grained soils in geotechnical engineering considering its stabilization and sustainability properties.

For the site investigation of stiff soils, dynamic penetration testing, such as standard penetration testing (SPT) and dynamic cone penetration testing (DCP), has been performed. The dynamic cone tip responses, however, have not yet been evaluated. The objective of this study is the development and application of an instrumented dynamic cone penetrometer (IDCP) to evaluate the dynamic cone tip responses by considering the energy transferred into the cone tip. As the preliminary study on the development of the IDCP, the energy losses caused by the rod connection are experimentally estimated and numerically analyzed by considering the transmission and reflection coefficients. Strain gauges and accelerometers are installed in the cone tip and rod head of the IDCP to detect dynamic responses during penetration. Design concerns include the shape of the IDCP, the installation of strain gauges and accelerometers, and the mechanical resistance calibration. The developed IDCP was driven into compacted weathered soils in the chamber to measure the dynamic responses at the rod head and cone tip. From the measured responses, the energy transferred into the rod head and the cone tip was calculated. The experimental and numerical energy loss studies show that the energy loss increases with an increase in the number of rod connections. The penetration-test results show that the energy transferred into the cone tip is significantly smaller than that transferred into the rod head. Furthermore, the energy corrected dynamic responses at the cone tip clearly detected soil layers. This study suggests that energy losses caused by rod connections should be considered and that the IDCP may be a useful tool for the characterization of stiff soils.

Resistance to permanent deformation is the primary performance indicator of unbound aggregate pavement layers. In relation to the applied wheel-load deviator stress, the shear strength property of a confined base/subbase controls the rate of permanent strain accumulation in that aggregate layer. The objective of this study was to quantify the impact of aggregate properties on the shear strength and permanent deformation characteristics of unbound aggregates. Sixteen different aggregates were studied in the laboratory for two different gradations: original quarry source and engineered midrange gradations. Aggregate specimens were prepared at these gradations to determine moisture-density relationships, and conduct monotonic and repeated load triaxial tests at the target maximum dry densities and optimal moisture contents. In addition, imaging-based aggregate particle shapes or morphological indices were obtained. The laboratory findings indicated that the particle size corresponded to 60% passing, and imaging-based angularity index contributed significantly to the increases in the shear strength properties of aggregates, which were also affected by density and moisture content. Permanent strain accumulations were primarily influenced by applied shear stress in relation to the shear strength of aggregates, and rutting model parameters obtained through regression analyses were influenced by applied stress, strength, and material properties. Further, an aggregate with plastic fines showed the highest permanent strain accumulation, hence clearly indicating the significant influence of plasticity of fines on the permanent strain accumulation.

The cementation factor is necessary to determine porosity via the Archie equation, and its range of values has been suggested in many previous studies. However, the cementation factors in the literature are limited to fully saturated conditions, and it may thus be inaccurate to use the same value in other saturation conditions. The objective of this study is to characterize how the cementation factor varies depending on the saturation percentage. In this study, glass beads and soil are selected as the specimens, and two relative density values, 40% and 80%, are selected. Time domain reflectometry (TDR) is used to obtain both the saturation and electrical resistivity of the specimens. TDR is installed in the cell, and fluid is continuously circulated from the bottom to the top of the porous material for 30 min. The estimated saturation increases with time and the electrical resistivity is reduced during the circulation. Finally, the cementation factor at every saturated stage is determined, and the error ratio based on the porosity is calculated to show the importance of the cementation factor. The results show that there is a high error ratio when an unsuitable cementation factor that does not consider the saturation condition is used. This study demonstrates that the method for determining the actual cementation factor using TDR and the Archie equation can be applied in various saturation conditions.

Dynamic resistance, which can be used to express strength in the unit of stress and improve the reliability of the dynamic cone penetration test (DCPT), has been estimated by numerous methods. This study aims to compare different dynamic resistance estimation methods by using an instrumented dynamic cone penetrometer (IDCP). DCPTs are conducted using a standard dynamic cone penetrometer (DCP) and IDCP in the laboratory and field. Dynamic responses are obtained from the strain gauges and an accelerometer installed at the cone tip of the IDCP. The test results show that dynamic resistance is more efficient in distinguishing profiles than the dynamic cone penetration index. Among the methods to estimate the dynamic resistance at the cone tip, the force-velocity integration method and force integration method are more related to the conventional dynamic resistance considering the potential energy of the hammer than the force squared integration method. Additionally, the dynamic resistance estimated for a longer time period is more reliable, particularly for small driving rod lengths. Regarding the limitation of the dynamic response from an accelerometer in a previous study, the force-based dynamic resistance estimated for a longer time period can be used as the most reliable approach for further soil strength characterization.

Fly ash, the main component for controlled low-strength material (CLSM), has physical and chemical characteristics according to the resources used in the thermal power plant, and thus fly ash type can influence the physical and strength properties of CLSM. This study investigates the effect of fly ash type on the engineering properties of CLSM and establishes relationships between mechanical properties of CLSM and shear wave velocity (SWV) for long curing times. Six fly ashes with different physical properties and chemical components are used for preparing the CLSM mixtures. The air content, unit weight, flowability, and setting time of CLSM are measured. Unconfined compressive strength (UCS) and elastic modulus (E) are obtained from unconfined compressive tests, and SWV (V_s) is determined using a bender element-based wave measurement system. Experimental results show that the stiffness and strength characteristics of CLSM are relevant to the contents of two oxides (SiO₂ and Al₂O₃) and the fineness of fly ash. Because the evolution of SWV is influenced by the fly ash type, the relationships UCS-V_s and E-V_s are well established. Thus, considering the fly ash type, shear wave monitoring may be effectively used for estimating strength and stiffness characteristics of CLSM.