ABSTRACT. Oenanthe L. is a taxonomically complex genus, several species of which have long been used as vegetables and traditional medicines in East Asia. In order to clarify the taxonomic status of Oenanthe accessions and provide baseline data for the sustainable use of its genetic resources, we examined sequence variations in the internal transcribed spacer (ITS) region of Oenanthe accessions collected from a wide geographical area in China and its neighboring countries. For comparison, ITS sequences in GenBank for almost all currently reported species of Oenanthe were also included in our analyses. Both phylogenetic tree construction methods (Bayesian inference and maximum likelihood) revealed that the accessions tended to cluster into two groups, which were closely related to O. mildbraedii and O. sarmentosa. However, these two species have never been recorded in China or its neighboring countries. Therefore, it seems probable that in our sampled locations, Oenanthe accessions have been given an incorrect name, such as O. javanica. Future studies should carefully check the morphological characteristics of other Oenanthe species and sequence their ITS regions in order to clarify the taxonomic status of the genus.

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The behaviour of pile-groups subjected to lateral soil pressure is a key consideration in establishing the design parameters of pile-groups. In this paper, one representative section of the Chongqing Jiangdong slope is taken as an example. The existence of an arching zone around pile groups for granular and fine-grained soils is first examined using the finite element computer code CORE-3D. Pile load-displacement curves and the arching effect are considered together to explain how the stresses are transferred from the soil to the piles. The key parameters controlling the soil arching effect are centre-to-centre pile spacing (S), thickness of stable soil mass (H), depth (L) of pile embedment, pile diameter (D) and these were studied extensively. An empirical equation summarising the results is presented and the results have been adopted by the designer in practice.

The factors resulted in the cracking of Xiao-wan arch dam are extremely complicated. A numerical analysis based on elastic-viscoplastic mechanics theory has been developed to study the cracks in the middle diversion pier of Xiaowan Arch Dam. This analysis aims to investigate the cause of cracks and the reliability and accuracy of the analysis model have been examined. By using this analysis and the obtained results, the following conclusions are drawn: 1) cracks were not induced by a single cause, but a multitude of various effect such as stresses induced by thermal movements, the bond between the anchor cables and the surrounding concrete and the pressure due to the impounded water, amongst which the thermal stress is the most significant reason; and 2) with the presence of water in cracks, if the drainage hole continues to run overflowing water, the stress intensity factor of a crack tip will exceed the fracture toughness of the concrete. With the hydraulic fracture effect, the crack will grow continuously. The findings derived from this study will provide useful information for future projects of the similar nature.

With the implementation of Western Development, West-to-East Electricity Transmission Project and South-to-North Water Diversion Project, a large number of hydro-power stations have been built in the west middleland regions of China. Because of the complexity of terrain, geological and physical-mechanical conditions, the stability of large underground structures becomes one of the most important problems during the engineering design, construction and operation. This paper will take Tianchi hydro-power station as an example, according to the measured stresses at several points, the in-situ stress field is feedback analyzed by using the combination of the genetic algorithm and 3D finite element method. Then, the rheological model of bolted joint rock and nonlinear finite element method are adopted to calculate the displacement field, stress field and D-P point safety factor of the underground structure. The stability of the underground structure is discussed, the excavating and supporting scheme are also presented, and the supporting effect is evaluated. The achievements in this paper can not only be taken as the reference to the design, but also provide some design experiences for other underground structures.