This paper presents a model-based approach to determine dielectric constants from time domain reflectometry TDR measurement in highly conductive soils. It makes use of information contained in the TDR signal from the reflection at the surface of the soil rather than the reflection from the end of the probe. The TDR method is widely used to determine the volumetric water content of soils. Commonly used information from the TDR signals includes the apparent dielectric constant and the electrical conductivity. The apparent dielectric constant is generally measured by analyzing the travel time of electromagnetic waves reflected from the end of the soil probe. In soils with high electrical conductivities, the attenuation of the signal can eliminate the reflection from the end of the probe, which limits the application of TDR to these materials. A simplified frequency-independent dielectric model is utilized to invert the dielectric constant from the reflected signals at the soil surface. Results indicate that the dielectric constant can be determined with reasonable accuracy by the proposed approach for soils with high electrical conductivity, where the conventional travel time analysis fails due to significant signal attenuation.

According to the results of cyclic triaxial tests on Hangzhou sands, a correlation is presented between liquefaction resistance and elastic shear modulus. Material-dependent but independent of confining stress, shows the linear relation of (sd/2)1/2 with Gmax. For its application to different soils, a method proposed by Tokimatsu [Tokimatsu K, Uchida A. Correlation between liquefaction resistance and shear wave velocity. Soils Found 1990: 30 (2):33-42] is utilized to normalize the shear modulus with respect to minimum void ratio. A simplified equation is established to evaluate the liquefaction potential by shear-wave velocity. The critical shear-wave velocity of liquefaction is in linear relation with 1/4 power of depth and the peak horizontal ground surface acceleration during earthquakes. The equation proposed in this paper is compared with previous methods especially the procedure proposed by Andrus [RD Andrus, KH Stokoe. Liquefaction resistance of soils from shear-wave velocity. J Geotech Geoenviron Eng 2000: 126 (11): 1015-25]. The results show its simplicity and effectiveness when applied to sands, but more validation or modification is needed for its application to sand with higher fines content.

微型桩（Micropile）和常规钻孔灌注桩相比，具有单位体积混凝土承载力高、施工场地小、适用各种类型的土、布置形式灵活等特点，可以用做输电线路杆塔基础。本文通过软土地基上微型桩的单桩、群桩抗压和抗拔现场试验，研究其荷载-沉降特性、群桩效应、施工工艺等，以期为微型桩的设计和施工提供依据。试验结果认为：单桩荷载-沉降曲线是缓变型，属摩擦桩，可以以20mm沉降量对应的荷载作为桩的极限承载力；可以以20mm～30mm上拔量对应的上拔荷载作为单桩极限上拔荷载；斜桩可以更好地承担上拔荷载。

Based on the Winkler hypothesis, a model for analysis of the flexural response of an ocean trestle embedded in layered soil to horizontal impact of a moving mass is developed. By use of the transfer matrix in time domain, one can calculate the flexural dynamic response of a single pile. Then, by use of the boundary conditions of piles at the pile top, the dynamic re-sponse of the structure is analyzed. By use of the model proposed in this paper, the interactive force between the moving mass and the structure can be computed based on Work's kinetic energy theorem and Newton iterative method. Thus the ap-proach does not have to assume the interactive force, while the traditional method have to. The approach more accords with the engineering practice than the traditional method and it is convenient for engineering design.

Moving ships and other objects drifting on water often impact a bridge’s pile foundations. The mechanical model of the piles-bridge structure under horizontal forcing was established, and a time-domain ap-proach based on Finite-difference Method was developed for analyzing the dynamic response of the piles-bridge structure. For a single pile, good agreement between two computed results validated the present approach. The slenderness ratio of the pile, the pile2soil stiffness ratio and the type of the structure influence the dynamic response of the piles2bridge structure. The computed results showed that the stiffness of the structure deter-mines the dynamic response of the piles2bridge structure under horizontal forcing.