ICSV 14 Cairns • Australia 9-12 July , 2007 THE PiP MODEL , A SOFTWARE APPLICATION FOR CALCULATING VIBRATION FROM UNDERGROND RAILWAYS
Significant vibration in buildings near underground tunnels is attributed to moving trains. Vibration is generated due to irregularities of wheels and tracks and propagates to nearby buildings causing annoyance to people and malfunctioning of sensitive equipment. Modelling of vibration from underground railways is gaining more interest on account of the need for quick tools to design vibration countermeasures for both existing and newly constructed tunnels. This paper describes a software application for calculating vibration from underground railways, called the Pipe-in-Pipe (PiP) model. The software has a user-friendly interface and is available on the internet as a freeware for engineers in charge of designing of vibration countermeasures in railway tunnels. The PiP model accounts for a train running on a floatingslab track in a tunnel embedded in the ground. The software calculates the Power Spectral Density (PSD) of the vertical displacement at any selected point in the soil for a roughness excitation of a unit value (i.e. white noise). It also calculates the Insertion Gain (IG) which is the difference in decibel between the displacement PSD after and before changing parameters of the track, tunnel or soil. The latest version of the software plots the displacement contours around the tunnel and accounts for a bedrock layer below the tunnel using the mirror-image method. The software is computationally efficient as it calculates results accurately and quickly on a personal computer unlike other available models of vibration from underground railways which take much longer time and require huge computational resources. A full description of the current version of the software is given in this paper along with ongoing developments that will appear in future versions.
A model for calculating vibration from a railway tunnel buried in a full-space including rigid bedrock
Subway induced vibration has become an important environmental problem. Ground borne noise and vibration have a signi cant impact on the comfort of inhabitants of buildings near railway tunnels. Therefore, legislation has become strict and the design of vibration countermeasures is of increasing importance. Engineers need accurate and fast running models. Over the last 10 years a computationally ef cient model, known as the Pipe-in-Pipe (PiP) model, has been developed. In its basic formulation, the PiP model accounts for a tunnel in a full space. Two methods are presented in this paper to account for a rigid bedrock underneath the tunnel. The rst is the mirror-image method and takes the bedrock into account by mirroring the tunnel and the applied load around the soil-bedrock interface. Vibration generated by the mirrored load represents the re ected wave eld. The mirror image method is very ef cient but it is only an approximation of the real boundary condition at the soil-bedrock interface. The second method is a new development of the PiP model and is based on the assumption that the near eld displacements are not in uenced by the existence of the rigid bedrock. Green's functions for a full space are used to calculate the internal source in a full space that would produce the same displacements at the tunnel-soil interface as calculated by the original PiP model (e.g. a tunnel in a full-space). This internal source is then used to calculate the far eld displacement by using Green's functions for a half-space with a xed surface. The two different methods are compared with an alternative Finite Element-Boundary Element (FE-BE) model, from which it is concluded that the modi ed PiP model produces more accurate results then the mirror-image method. ICSV14  912 July 2007  Cairns  Australia
Vertebral Fusion in Two Early Jurassic Sauropodomorph Dinosaurs from the Lufeng Formation of Yunnan, China
Here we describe two instances of pathological vertebral fusion in two genera of sauropodomorph dinosaurs from the Early Jurassic Lufeng Formation in Yunnan, China. The first is a specimen, of Lufengosaurus huenei with two fused cervical vertebrae, and the other is a specimen of the Lufeng basal sauropod, with two fused caudal vertebrae. Both pathologies are consistent with spondyloarthropathy and represent the earliest known occurrence of that disease in dinosaurs. The two specimens affirm that early dinosaurs suffered from the same bone diseases as living vertebrates. Spondyloarthropathy in these dinosaurs may have been induced by long-term mechanical stress, such as weight bearing, and/or limited motion at the joint that would otherwise have inhibited such remodeling. In both cases, surface remodeling suggests that the animals survived well beyond the initiation of spondyloarthropathy.