Soda residue (SR), a waste by-product of sodium carbonate production, occupies land resources and pollutes the environment seriously. To promote the resource reusing of waste SR, this paper studies the feasibility of utilizing SR for the preparation of soda residue soil (SRS) through laboratory and field tests. The SR and fly ash (FA) were mixed with six different proportions (SR:FA is 1:0, 10:1, 8:1, 6:1, 3:1, 1:1) to prepare SRS, and the optimum water content, maximum dry density, shear strength, and unconfined compression strength of the SRS were measured. The representative SRS (SR:FA is 10:1) was selected to investigate the compression performance and collapsibility. The preparation and filling method of SRS in the field was proposed, and the effects of gravel, sand, and lime on the mechanical properties of SRS were studied through field tests. The results show that the addition of FA contributed to the strength development of SR, and the addition of lime, sand and rubble have a significant effect on the subgrade bearing capacity of SRS. The subgrade bearing capacity and deformation modulus of SRS in field tests is more than 210 kPa and 34.48 MPa, respectively. The results provide experimental basis and reference for the preparation of SRS, the scientific application of SRS in geotechnical engineering to promote sustainable development.

A series of direct shear tests using a large-scale constant-normal-stiffness direct-shear testing system was conducted to study the factors that influence the mechanical characteristics of a pile–soil interface (PSI) in clay soil. Interfaces of different roughness (R = 0, 2, 4, and 6 mm) were tested in clay soil with four different water contents with four normal stresses under different shear rates during shearing. Results for the interfacial shear behavior are presented as shear-stress–shear-strain curves, shear strength, and parameters. The results show that (i) the higher the roughness, the higher the shear strength of the PSI. The larger the normal stress, the smaller the roughness effect on the shear strength and parameters of the PSI; and (ii) the higher the water content of the clay soil, the lower the shear strength of the PSI, with maximum cohesion at a water content of 25%. The main influence that increasing the water content has on the shear strength of the PSI is changing the coherence, while the shear rate in this test range has less effect on the shear strength of the PSI. Overall, the mechanical characteristics of the PSI are influenced by roughness, water content, and shear rate, and close attention should be paid to those three factors when analyzing test results.

Prestressed high-strength concrete (PHC) pipe pile with the static press-in method has been widely used in recent years. The generation and dissipation of excess pore water pressure at the pile–soil interface during pile jacking have an important influence on the pile’s mechanical characteristics and bearing capacity. In addition, this can cause uncontrolled concrete damage. Monitoring the change in excess pore water pressure at the pile–soil interface during pile jacking is a plan that many researchers hope to implement. In this paper, field tests of two full-footjacked piles were carried out in a viscous soil foundation, the laws of generation and dissipation of excess pore water pressure at the pile–soil interface during pile jacking were monitored in real time, and the laws of variation in excess pore water pressure at the pile–soil interface with the burial depth and time were analyzed. As can be seen from the test results, the excess pore water pressure at the pile–soil interface increased to the peak and then began to decline, but the excess pore water pressure after the decline was still relatively large. Test pile S1 decreased from 201.4 to 86.3 kPa, while test pile S2 decreased from 374.1 to 114.3 kPa after pile jacking. The excess pore water pressure at the pile–soil interface rose first at the initial stage of consolidation and dissipated only after the hydraulic gradient between the pile–soil interface and the soil surrounding the pile disappeared. The dissipation degree of excess pore water pressure reached about 75–85%. The excess pore water pressure at the pile–soil interface increased with the increase in buried depth and finally tended to stabilize.