Abstract

Based on the principle of the Panda® penetrometer, a third-generation of variable-energy dynamic cone penetrometer has been developed in France: the Panda 3(1). This is an instrumented dynamic penetrometer which, by measuring strain, acceleration, and displacement on the rods, close to the anvil, and then decoupling the deformation waves created by the impact and propagating within the rods during penetration, makes it possible to obtain for each blow, at the soil/cone interface, a dynamic load penetration curve, called DCLT curve. Several experimental and numerical studies have been carried out to develop different techniques for processing DCLT curves and dynamic signals to assess input energy, dynamic and pseudo static cone resistance, dynamic stiffness, elastic modulus, and compressional wave velocities of soil. This technique has been adapted to the DPSH cone penetrometer (ISO 22476-2), for which it was necessary to servoassisted the impact force as a function of the soil penetration obtained after each blow to improve then the quality of the signals and DCLT curves obtained. Recently, in France, a vast experimental program involving two universities and two geotechnical companies was carried out to develop this new technique. A large laboratory and in-situ test data base was performed. After a brief presentation of the theoretical and technological development of this new technique is presented.

Abstract

We consider a space-time variational formulation of the second-order wave equation, where integration by parts is also applied with respect to the time variable. Conforming tensor-product finite element discretisations with piecewise polynomials of this space-time variational formulation require a CFL condition to ensure stability. To overcome this restriction in the case of piecewise multilinear, continuous ansatz and test functions, a stabilisation is well-known, which leads to an unconditionally stable space-time finite element method. In this work, we generalise this stabilisation idea from the lowestorder case to the higher-order case, i.e. to an arbitrary polynomial degree. We give numerical examples for a one-dimensional spatial domain, where the unconditional stability and optimal convergence rates in space-time norms are illustrated.