L'article suivant donne une description de la methode theorique pour le calcul du danger d'un soulevement du fond d'une fouille cadragee dans l'argile. Terzaghi et Tschebotarioff ont deja donne des formules pour un pareil calcul, mais ces formules ne sont valables que pour des fouilles de petite profondeur. Basee sur les formules de la capacite portante des fondations dans l'argile, une nouvelle solution du probleme de soulevement du fond a ete developpee. La profondeur critique d'une fouille est donnee par : D c = N c . S/γ ou s et γ sont respectivement la resistance au cisaillement et le poids d'unite de l'argile, N c etant un coefficient sans dimension et dependant de la forme de la fouille, c'est-a-dire de la proportion largeur-longueur et de la proportion profondeur-largeur. Les valeurs de N c , identiques aux valeurs donnees par Skempton (1951) pour la capacite portante, sont montrees graphiquement dans la Figure 2. La validite de ces formules a ete examinee par comparaison de quatorze fouilles. Dans sept de ces fouilles, un soulevement total du fond a eu lieu, les coefficients theoriques de securite donnant comme valeur moyenne de 0,96. Quatre fouilles, ou on constatait un soulevement partiel du fond, ont fourni une valeur moyenne des coefficients theoriques de securite de 1,11. Les trois dernieres fouilles ont ete accomplies sans evenement speciaux, mais des observations sur place indiquaient que, avec une profondeur agrandissante, on aurait du craindre un soulevement du fond, la valeur moyenne des coefficients theoriques de securite etant de 1,08. Les resultats obtenus ci-dessus montrent, ainsi, que la methode decrite nous permet d'estimer avec une precision suffisante le danger d'un soulevement du fond d'une fouille dans l'argile, et que la methode suffit pour la plupart des usages pratiques.

Stability of strutted excavations in clay

Statistical analysis of fire accidents in Chinese highway tunnels 2000–2016

Effect of particle shape on the progressive failure of shield tunnel face in granular soils by coupled FDM-DEM method

Postconstruction settlement that occurs before a tunnel is in operation may significantly influence the tunnel’s long-term stability. The current study investigates such a tunnel, a three-l...

Investigating the Long-Term Settlement of a Tunnel Built over Improved Loessial Foundation Soil Using Jet Grouting Technique

The Qingling–Bashan (QB) mountain region in southern Shaanxi mainly consists of strongly compressive zones from east to west, with tight folds and compressive fractures. There is a wide distribution of soft rocks of various types, such as phyllite and slate, accompanied by complex geological structures. Ironically, tunnel construction in these difficult grounds with complicated geological conditions embraces a high risk of extreme deformation due to various unpredictable reasons, which can frequently cause collapse and result in budget overruns during the construction period. Therefore, it is crucial to conduct effective countermeasures to eliminate or avoid such adverse impacts. This paper provides a case study on the “Yingfeng tunnel” (a tunnel constructed in soft rock consisting of a slate ground) based on a geological survey, indoor experiments and in situ monitoring. A successive rock mass deformation resulted in the tunnel lining seriously intruding into construction clearance and some other sections, even collapsing during the construction. The maximum displacement amount was 62.5 cm, while the maximum deformation speed reached as high as 34.18 mm/day. Additionally, to evaluate the construction impacts of tunnelling-induced geo-hazards, an investigation on extreme deformation was conducted. Considering the time-dependent features of the rock mass deformation, the constraint-convergence method was used to put forward applicable countermeasures in this paper. Finally, from the feedbacks of monitoring results, extreme deformation of the Yingfeng tunnel was effectively controlled.

Pengfei Li

Papers

Displacement characteristics of high-speed railway tunnel construction in loess ground by using multi-step excavation method

An upper-bound analytical model of blow-out for a shallow tunnel in sand considering the partial failure within the face

Displacement characteristics of high-speed railway tunnel construction

Experimental investigation of mechanical characteristics for linings of twins tunnels with asymmetric cross-section

Stability analysis of the middle soil pillar for asymmetric parallel tunnels by using model testing and numerical simulations