[雙語翻譯]擋土墻外文翻譯--干砌石擋土墻具有抗拉強度的延性工程結構（英文）

1、Drystone retaining walls: Ductile engineering structures with tensile strengthPaul F. McCombie a,?, Chris Mundell b, Andrew Heath a, Peter Walker aa BRE Centre for Innovative Construction Materials, Department of Archite

2、cture and Civil Engineering, University of Bath, Bath BA2 7AY, UK b Atkins, The Hub, 500 Park Avenue, Aztec West, Bristol BS32 4RZ, UKa r t i c l e i n f oArticle history:Received 20 March 2012Revised 12 June 2012Accepte

3、d 27 June 2012Available online 2 August 2012Keywords:Retaining wallsDrystoneDuctilityAssessmenta b s t r a c tDrystone retaining walls are sustainable engineering structures constructed with locally obtained naturalstone

4、. They were commonly built with very slender profiles compared with modern mass-masonry struc-tures, leading to a common belief among engineers that they have very low margins of safety. Thesestructures remain critical t

5、o the transport infrastructure in many parts of the world, and have provento be very durable, yet very few new drystone retaining walls are built, and walls which do fail are usuallyreplaced with concrete constructions.

6、We show that these walls are ductile even though their compo-nents are brittle, and have tensile strength through the interlocking of their stones, even though theyare assembled without any cohesive material such as mort

7、ar. These properties are critical to a properunderstanding of their behaviour and durability. Full-scale testing of five drystone retaining walls hasshown that bulging, most commonly regarded as a sign of incipient failu

8、re, begins as a ductile adaptationof the geometry to the loads imposed on it. Localised bulging can be a consequence of small defects inconstruction or foundation conditions, or concentrated loading, and may be sustained

9、 indefinitely in awall which is in general well-constructed. These insights into the behaviour of walls allow the designof new walls which use materials efficiently, and enable existing walls to be kept in service, and m

10、ayinspire new ways of achieving ductility in engineering materials.? 2012 Elsevier Ltd. All rights reserved.1. IntroductionDrystone walling is an ancient technique in which locally sourced stones are carefully assembled

11、by hand following tradi- tional practices to construct field walls, buildings, and earth- retaining structures. Until recently the behaviour of these struc- tures was not well understood. Typical retaining walls were bui

12、lt with a much more slender profile than modern mass-masonry structures, and it is a common belief among engineers that they have very low margins of safety [1], so structures with a distorted profile are presumed to be

13、‘distressed’ even though it is known that they can remain stable for decades. Drystone retaining walls re- main critical to the transport infrastructure in many parts of the world, as well as shaping the ground to form t

14、erraces for housing and agriculture. Even though they are sustainable, using locally sourced unmanufactured materials and skilled labour, and are aes- thetically pleasing, when a drystone wall reaches the end of its life

15、 it is usually replaced with concrete, and very few new drystone retaining walls are built. Despite the importance of drystone retaining walls to transport infrastructure, very little research has been undertaken. Four w

16、allswere built and tested to destruction in Ireland in 1834 [2], while a further four walls retaining water-filled bags were loaded to initial yield in France [3]. Extensive numerical analysis has been done on the Irish

17、walls using the Finite Element Method [4] and the Dis- crete Element Method [5,6], even though relatively little informa- tion on their properties is known and the walls were not instrumented during testing. This previou

18、s work demonstrated the impracticality of using such methods other than as experimen- tal tools, owing to the difficulty and complexity of making a realis- tic model. Nevertheless, it is useful to have such experimental

19、tools, and some of the equilibrium analyses carried out for compar- ison with the numerical modelling results gave useful insights into wall behaviour. In particular, the significance of rotation of individ- ual blocks h

20、as been highlighted, which does not occur in conven- tional mass retaining walls [6].2. Full-scale testing2.1. Test configurationTo address a pressing need for detailed observations of the behaviour of real walls, five t

21、est walls were built as summarised in Table 1, each 2.5 m high and over 12 m long, with a central test section built on a steel platform which could be raised, lowered and tilted under fine control using motorised screw

22、jacks. Hinged0141-0296/$ - see front matter ? 2012 Elsevier Ltd. All rights reserved.http://dx.doi.org/10.1016/j.engstruct.2012.06.046? Corresponding author. Tel.: +44 1225 826629; fax: +44 1225 386691.E-mail addresses:

23、P.F.McCombie@bath.ac.uk (P.F. McCombie), Chris.Mundell@atkinsglobal.com (C. Mundell), A.Heath@bath.ac.uk (A. Heath), P.Walker@bath.ac.uk(P. Walker).Engineering Structures 45 (2012) 238–243Contents lists available at SciV

24、erse ScienceDirectEngineering Structuresjournal homepage: www.elsevier.com/locate/engstructstress concentrations in the wall and backfill behind the wall, information from the pressure cells which were installed was of l

25、imited use. Deformations observed during backfilling were small in relation to the height of the walls.2.2. Testing to destructionFollowing the raising of the platform, a load was applied to the surface of the gravel beh

26、ind the top of each wall via a 600 mm square plate, as seen in Fig. 1. The walls began to yield when loads of between 6 and 11 tonne (60 and 110 kN) were applied to this plate, with final collapse occurring only after co

27、nsiderable defor- mation, as indicated in Table 1. Prior to the final collapse, the load could be removed and all movement of the structures would cease. The walls are shown at their maximum deformations prior to col- la

28、pse in Fig. 2. The targets attached to the wall face were horizontal prior to the application of load to the top of the backfill, and hence indicate the rotation of stones at the face. The horizontal sliding of the slate

29、 in Wall 5 is conspicuous, as is the extreme inclination of Wall 1, which was supported by tension along the face of the wall, which resulted in a catenary in plan extending from the lightly loaded section to one side wh

30、ich carried only pressure due to the self-weight of the backfill, through the central test section, to the lightly loaded section on the other side. This is discussed further below. Careful observations were made during

31、the loading of the walls, in addition to the measurements, by multiple still cameras, a continuously recording high definition video camera, and the team of investigators. The observed deformations were seen to arise pri

32、marily from the accumulated effects of small rotations of individual stones, but as displacements increased sliding of stone on stone became important. The section of wall carrying the ap- plied load bulged out relative

33、to the adjacent sections, stretching as it did so.2.3. ObservationsThe first test wall was constructed following best drystone wall- ing practice, with good bonding – that is, the stones on successive courses overlapped

34、each other throughout, so that if a stone was pushed forwards, it pulled the stones above and below it through a frictional interaction; these stones in turn pulled the stones on either side of the first stone in the sam

35、e way. Thus a tensile con- nection was established between the first stone and the stones on either side purely as a consequence of the frictional connection with the stones above and below. This tensile strength is simi

36、lar to that which develops in a natural fibre rope, which is made up of short strands which transfer load via friction, which is maintained by the lateral compression generated by the twist of the strands. Laboratory tes

37、ts confirmed that the coefficient of friction for the limestone used is high, which with the weight of wall above anygiven course produces a strong frictional resistance. Normally in engineering construction a tensile co

38、nnection is a weak link: if the material is brittle then once the tensile strength is exceeded a failure is inevitable. Ductile behaviour is much preferred, so that rather than simply breaking once a yield load is achiev

39、ed, the material stretches significantly. This can allow load to be trans- ferred to adjacent elements with spare capacity, or at least give warning that a failure is approaching. The tensile strength arising from fricti

40、onal interaction is ductile in nature, in that until dis- placements are so great that stones lose contact with each other completely, the frictional interaction will persist with approxi- mately the same strength. This

41、tensile strength along the line of the wall provides a mech- anism for transferring load from one section of wall to another, so that local overloading does not result in immediate failure. It is not, however, the only m

42、eans by which the structures behave in a duc- tile manner and maintain their stability. Walls 1 and 2 were both built with the stones very tightly packed together (the voidage, or percentage of volume not occu- pied by s

43、tone, is given in Table 1). Wall 2 was built to a higher overall density because of its reduced width, making it very slen- der, and was deliberately constructed with vertical running joints. That is, some of the gaps be

44、tween the stones were aligned up the height of the wall, disrupting the tensile strength along the length of the wall and allowing the test section to move more freely. The tightly packed stones left little room for inte

45、rnal deformation as the load increased, and the failure mode was principally a forwards rotation of the entire wall over its toe (that is, the front of its base), reflecting conventional assumptions about the behaviour o

46、f gravity walls. The wall was unusually slender for a gravity wall, with a base width only 25% of the retained height. This was only possible because of the stabilising effect of the downdrag force on the back of the wal

47、l, resisting the overturning moment from the horizontal component of earth pressure. Whilst this force had been induced in a controlled manner by the raising of the wall against the backfill, simulating backfill settleme

48、nt, it would also have been generated as the wall began to rotate forwards, so lifting up at the back. Wall 3 was deliberately built much more quickly with a lower density, and a quality of construction which better refl

49、ected com- mon historic practice in the field. Modern professional drystone wallers work to very high standards, producing densely built walls with very few running joints and sufficient through-stones, which span from t

50、he front to the back of the wall and hold it together. The packing of the stone in Walls 1 and 3 is compared in Fig. 3. Wall 3 included running joints, as in wall 2. The lower density permitted noticeable rotation of ind

51、ividual stones as load was applied. For the most part, such rotations were through relatively small anglesfrom a position which was stable during construction to a position which was stable under the applied loading. The