Vol 53, No 6 (2017)

The methods of calculating the filtration coefficient k from data obtained in tests performed under the conditions of one-dimensional consolidation in terms of consolidation coefficient c_v, compressibility a_v and volume compressibility m_v, average particle size D₁₀, and void ratio e are investigated. The evaluated k used in the PLAXIS software system is taken for comparison. The filtration coefficients determined by different methods were used to study the scale effect in the Mohr-Coulomb model. The excess pore pressure for different diameter to height ratios of a sample was in better agreement with the values predicted by using k determined in PLAXIS. This is explained in part by the variability of the filtration coefficient during consolidation.

Sand lenses in clay layers may have various shapes and sizes. In many geotechnical studies, their effects are not considered carefully since detection of their positions and characteristics is difficult. In the simulation of the consolidation in clay layers with imbedded sand lenses, the problem can hardly be taken as a one-dimensional problem, and the phenomenon should be considered as a two- or three-dimensional problem. In the present study, the effect of the existence of sand lenses is investigated in terms of their positions and drainage characteristics in two-dimensional space. All drainage boundary conditions, including the boundary of lenses, are considered to be time dependent due to their variable thicknesses and permeability coefficients. A least squares based mesh free technique is used to solve the governing equations. In this method, radial basis functions are applied in function approximation. The results show the significant effect of the lenses and their characteristics in the process of dissipation of excess pore water pressure.

A new detection method using lateral excitation to test pile integrity is proposed. Concrete piles were subjected to lateral excitation, which produced transverse waves. These waves were processed with the Hilbert-Huang Transform (HHT), and the results were compared with those of a nondestructive testing method based on vertical excitation. The locations of the defects in the pile body detected by the lateral excitation method agree well with those derived by the vertical excitation method, which indicates that HHT analysis of the lateral acceleration wave signal obtained by HHT can detect defects in a pile body. Thus, lateral excitation technology can be applied in integrity assessments of pile foundations that have constraints or structural limits on their top.

Several types of deterioration have developed at earthen sites of the Ming Great Wall in Qinghai Province, including cracks, gullies, collapses, sapping, and scaling off, the first four of which could threaten the wall's stability. The correlations of these types of deterioration with each other and with other factors were explored. The authors selected 16 sampling points from nine typical earthen sites of the wall to investigate its deterioration. Linear fitting of the data on the types of deterioration was conducted to determine their correlations. Then, indoor tests of these samples were systematically performed to clarify the physical, water-related, and mechanical properties of the rammed earth, and meteorological data for each county were collected. Finally, the linear fitting was carried out among the deterioration indices, engineering-related parameters of the rammed earth, and meteorological data to determine the influence of these factors on the development of each type of deterioration. This research illustrates the mechanisms involved in such deterioration and its evolution from a macro perspective.