Caractérisation améliorée des sols par l'essai de chargement de pointe au piézocone. Application au calcul des fondations profondes

Hassan Ali 1
1 Laboratoire de Mécanique et Ingéniéries
LAMI - Laboratoire de Mécanique et Ingénieries
Abstract : The Cone Loading Test (CLT) is a new in situ test, which constitutes a major improvement to the piezocone penetration test (CPTu). The cone loading test consists in stopping the penetration (EN ISO 22476-1) at a desired depth, and carrying out a loading of the cone by successive load steps until the ground failure.The obtained loading curve, which relates the pressure applied on the cone in each step, to the cone settlement, is rich in information regarding soil deformability. Therefore, the test allows improved soil characterization by providing deformability parameters as well as the strength parameters obtained during a CPT test.The validation of the cone loading test method was conducted by three complementary approaches: experimental, numerical and physical.Several test campaigns were conducted on different sites such as the Merville site (Flanders clay), and two sandy sites in Utrecht (The Netherlands), and Limelette (Belgium). The results of these campaigns have shown that loading curves can be obtained for a modulus calculation, which is comparable to the other investigation tests moduli. The test is suitable for varied soil types. It is more representative of the initial soil state than other test types. Furthermore the boundary conditions are well controlled.In the numerical approach performed with Plaxis finite element modelling software, an important parametric study was done, in order to test the influence of cone geometry, loading type, behaviour model, soil parameters, initial conditions and boundary problem. CLT tests were also performed on reduced scale models in a geotechnical centrifuge. The objective was to test the influence of some parameters such as the loading rate, the cone geometry, the soil density and the level of g. These tests were associated with instrumented pile loading tests as well as shallow and deep foundation tests in order to link the mechanical parameters of the CLT test to the structures' behaviour. By considering that the cone penetrometer is a reduced pile model, a very practical and interesting outcome is the potential of the cone loading test to be a foundations dimensioning tool. For this purpose, a direct method using the cone resistance and limit side friction of the CLT was proposed to calculate the bearing capacity, and predict the pile settlement. Thismethod is a new approach transforming the loading curves and those of friction mobilization of a CLT, point by point to a load-settlement curve of a pile (t-z curves).
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Engineering Sciences. Université Blaise Pascal - Clermont-Ferrand II, 2010. French. <NNT : 2010CLF22059>


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Hassan Ali. Caractérisation améliorée des sols par l'essai de chargement de pointe au piézocone. Application au calcul des fondations profondes. Engineering Sciences. Université Blaise Pascal - Clermont-Ferrand II, 2010. French. <NNT : 2010CLF22059>. <tel-00629642>

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