A Novel Excavation and Construction Method for an Extra-Long Underwater Tunnel in Soft Soils

The cut-and-cover technique is widely used in the field of tunnel engineering owing to its simple construction technology, high working efficiency, and low cost. However, the safety of the foundation pit and the environmental impact during excavation are of great concern, especially for tunnels that pass through lakes and/or rivers. In this paper, a novel excavation and construction method is presented for the Taihu tunnel, which is the longest lake-crossing tunnel in China. In this method, a cofferdam of double-row steel sheet piles (DSSPs) was designed in order to divide the overlying excavation into several closed zones. During the construction, four zones were regarded as a unit, and different construction steps were carried out simultaneously in each zone. Therefore, an assembly line for the tunnel excavation was established to accelerate the construction speed. The most distinctive advantage of this method is that the excavation did not cut off the normal flow of the lake water and the shipping routes, with low environmental impact. To investigate the tunnel deformation during excavation, a finite element analysis combined with field monitoring data was adopted, indicating that the magnitude of the tunnel deformation was notably less than those reported from other excavation projects. Moreover, the effect of groundwater on the piles and the safety of the foundation pit was revealed using numerical modelling. This study provides a new idea for the design and construction of tunnel engineering, especially for extra-long underwater tunnels in soft deposits.

Unges dialektbrug i bygden Sandur på Færøerne

In this article, dialect changes and variation among young schoolchildren in the island of Sandoy in the Faroe Islands are discussed. The fieldwork was made by a group of students at the University of the Faroe Islands in November 2019 under the guidance of this article’s author. The informants are two groups of 10 and 15 year old schoolchildren. By examining the young generation, we can get information about the ‘state of health’ of the dialect. Here three dialectal variables are examined: (i) The variation of definite and indefinite form of words for family members, for instance the dialectal form mamman ‘the mother’ and the Central Faroese form mamma ‘mother’; (ii) Personal and possessive pronouns in 1st and 2nd person plural in oblique case, for instance the dialect form [o:gʊn] ‘us’ and the Central Faroese form [ɔʰk:ʊn] ‘us’; (iii) The pronunciation of short ó with the dialectal variant [ɔ] and the Central Faroese form [œ], for instance [fɔlk] resp. [fœlk] ‘people’. The first variable shows clearly a tendency towards dialect change in the young generation: the indefinite forms are much more frequent than the dialect counterpart. The use of the pronouns shows a relatively high degree of variation: the dialect forms are more frequently used by the 10 than the 15 year old pupils. The pronunciation of short ó shows variation to a large extent. Here we see the same pattern as we saw for variable 2: the youngest pupils are more likely to use the dialect¬al form [ɔ] than the older ones. On the other hand, variation is much more common in the group of 15 year old pupils. This study shows both stability and change in the dialect of children in Sandoy: Stability in use of the dialectal forms of the personal and possessive pro¬nouns, and variation and change in the two other variables. In a couple of years an underwater tunnel will connect the island of Sandoy with the central part of the islands. In a future scenario this dialect study opens the possibility for comparative studies of the dialect of Sandoy before and after the opening of the tunnel.

A measure of control of submerging and surfacing of an Autonomous underwater vehicle for exploring underwater of rivers

Autonomous underwater vehicle (AUV) known, as a special purpose underwater research vehicle (SPURV) is really a pocket submarine that could be used in multipurpose such as meteorology, probing the pollution of stream, military spying, exploring an underwater tunnel or wrecked ships and other purposes. With the reason of the power of battery inside of AUV is limited, the aim of this paper is to represent an effect way of control the submerging and surfacing of an AUV in order to save energy for a longer time service or a deeper and further expedition under water. In fact, there are so many ways for saving energy of the battery of AUV and in this paper, the selection of keeping permanently the horizontal direction of the AUV in any operation as the situation of a real submarine is applied. The diving and surfacing of AUV are consigned to the motor of the pump that consumes a little of energy to keep the proportion of the weight and the Archimedes force by pumping water inside or outside of the AUV. The selection of volume of pumped water is considered as a dynamic ballast mass for maintaining the horizontal equilibrium of the AUV at the time of submerging and surfacing. In the other hand, the controlling of the gravity point of AUV for maintaining a fixed position of gravity of the AUV when submerging and surfacing are the main factors of the paper that is also investigated in this paper. Finally, the motor of the propeller or thruster that always spends a great energy has committed only for forward or backward motion of the AUV. In this measure, the motor of thruster does not confronted with a great consummation of energy when submerging and surfacing in an oblique direction as almost all popular measures of control of AUV.