The dynamic characterization of concrete is fundamental to understand the material behavior in case of heavy earthquakes and dynamic events. The implementation of material constitutive law is of capital importance for the numerical simulation of the dynamic processes as those caused by earthquakes. Splitting tensile concrete specimens were tested at strain rates of 10⁻⁷ s⁻¹to 10⁻⁴ s⁻¹in an MTS material test machine. Results of tensile strength versus strain rate are presented and compared with compressive strength and existing models at similar strain rates. Dynamic increase factor versus strain rate curves for tensile strength were also evaluated and discussed. The same tensile data are compared with strength data using a thermodynamic model. Results of the tests show a significant strain rate sensitive behavior, exhibiting dynamic tensile strength increasing with strain rate. In the quasistatic strain rate regime, the existing models often underestimate the experimental results. The thermodynamic theory for the splitting tensile strength of concrete satisfactorily describes the experimental findings of strength as effect of strain rates.

In the process of large‐scale urban construction, large amounts of waste slurry are produced. The slurry has a high water content and is difficult to precipitate naturally, resulting in low treatment efficiency. To improve the treatment efficiency of slurry, a variety of inorganic and organic polymer flocculants were used to carry out flocculation settlement tests on the slurry. The changes in the slurry properties and the filtration dewatering effect after flocculation were tested. The results show that the addition of flocculant makes the slurry particles form aggregates, which leads to rapid precipitation of the slurry. The use of an inorganic flocculant significantly reduced the zeta potential of the slurry. Organic polymer flocculant, however, had little effect on the slurry potential, but did cause the slurry to produce larger size aggregates, resulting in a better flocculation effect than inorganic flocculant. Inorganic flocculants and organic flocculants can improve the pressure filtration dewatering performance of slurry. CPAM12 (cationic polyacrylamide, with a relative molecular weight of 12 million Daltons) had the best overall effect. The formation of aggregates after flocculation and the change in the nonuniformity coefficient (C_u) were the main cause of improvement of pressure filtration dewatering performance of the slurry. When C_u decreases from 11.85 to 8.75, the time required for pressure filtration stabilization is shortened by 70%. The nonuniformity coefficient of flocculated slurry can be used to evaluate flocculants, determine the optimal dosage, and predict the dewatering effect.

Yangtze River tunnel in Nanjing, China, was constructed by slurry shield tunnelling method. Along the 3020m tunnel, one of the construction difficulties is to pass through a gravelly sand stratum. As this stratum is highly permeable subjected to an elevated water pressure, one of the key issues is the formation of filter cake for a stable cutting face during tunnel excavation. To solve this specific engineering problem, a series of permeability tests were carried out on samples taken from the gravelly sand stratum and slurry materials used in the Yangtze River tunnel project. A new apparatus was developed to simulate the filter cake formation on the surface of the gravelly sand under elevated pressure, through which the quantities of the discharged water were measured. The effects of clay content of the slurry on the thickness and permeability of filter cake were studied. The test results indicated that the clay content of the slurry played an important role in the filter cake formation. The amount of seepage through the gravelly sand and the thickness of the filter cake decreased with the increasing of the clay content in slurry.