A numerical model for the tunnel boring machine interaction with soil
Mechanized shield tunnelling is a reliable way of constructing tunnels in soft soil, particularly in urban areas. However, a lack of understanding of the physical interaction between the TBM-shield, the soil, and the process fluids contributes to the long learning curves often experienced and hinders improvement of the machine’s driving rationality. A numerical shield-soil interaction model is proposed that bases the extent and spatial distribution of the displacements induced by the advancing shield on TBM monitoring data. The model includes the unloading-reloading condition of the surrounding soil and the possible infiltration of process fluids around the shield periphery. This infiltration influences the equilibrium of the TBM. A set of novel soil reaction curves is also introduced specifically to model a TBM interaction with the surrounding soil. The study offers an innovative outlook on the tunnelling related soil displacements. Results indicate that a more rational approach to mechanized shield tunnelling in soft soil is possible.
Theoretical Model of Shield Behavior During Excavation. I: Theory
Closed-type shield tunneling methods were developed together with computer-aided automatic control systems. However, automatic control systems are based on empirical relationships and do not have a precise theoretical background. In this paper, a model of the theoretical dynamic load acting on the shield during excavation is developed, taking into account shield tunnel engineering practices; i.e., the excavated area, the tail clearance, the rotation direction of the cutter face, sliding of the shield, ground loosening at the shield crown, and the dynamic equilibrium condition. To evaluate the validity of the model qualitatively, the simulation of shield behavior and the sensitivity analysis of the model parameters on the shield behavior are carried out in both straight and curve alignments for both sandy and clayey ground. The results for the shield behavior are examined, comparing them with the empirical and the theoretical one, and it is confirmed that the proposed model represents the shield behavior reasonably well.
The Impact of EU Unfair Contract Terms Law on U.S. Business-to-Consumer Internet Merchants
When the Court of Appeals for Versailles issued its decision in AOL France v. UFC Que Choisir2 in September 2005, it sent the message to U.S. Internet businesses that even contractual boilerplate localized for European markets may be invalid in European consumer transactions. In that case, a French consumer advocacy group challenged the terms AOL offered its French customers after AOL had made extensive revisions to its standard form contracts to respond to the concerns regarding those terms expressed in an advisory opinion by a French consumer protection agency. In 2004, a trial court invalidated nearly every term in the revised agreement; the appeals court affirmed on all counts. Subsequently, in July 2006 following concerns raised by the Office of Fair Trading (“OFT”), a United Kingdom government agency charged with “making sure markets work well for consumers,”3 Dell Corporation Limited changed its online terms and conditions to make them fairer to consumers.4 European consumer contract law had an impact in both cases. At issue for AOL France and Dell Corporation Limited was the application of France’s and the UK’s consumer contract law which is based on the Unfair Contract Terms Directive of 19945 and calls into question the validity of many of the terms that U.S. courts routinely enforce in transactions involving American consumers and merchants.