Development of a hybrid soil pressure sensor and its application to soil compaction

A new soil pressure sensor based on a combination of the deflecting membrane and fluid-filled approaches has been developed. The advantages of this combined approach are that issues of sensor compliance are eliminated without reducing the effectiveness of the sensor to be used for dynamic measurements. Calibration and verification testing performed under controlled laboratory conditions illustrate these benefits. The new system was implemented in a full-scale field trial that involved the construction of a compacted engineered fill 1.8 m in height. As each layer of fill was placed and compacted, vertical in-soil pressure and vertical in-soil strain were continuously measured. During the vibratory compaction process both vertical soil pressure and vertical soil strain histories were captured in each layer. The data collected allowed for the determination of fill stiffness for both static and dynamic conditions. The results illustrate the effect of both confining pressure and strain level on fill stiffness. The relationship between compaction pressure and depth is clearly defined. Key words: soil pressure measurement, soil stiffness, dynamic measurements, compacted fill. Un nouveau capteur de pression du sol base sur une combinaison de la membrane deflectrice et des approches de remplissage de fluide a ete developpe. Les avantages de cette approche combinee sont que les problemes de conformite des capteurs sont elimines sans reduire l'efficacite du capteur a utiliser pour les mesures dynamiques. Les tests d'etalonnage et de verification effectues dans des conditions de laboratoire controlees illustrent ces avantages. Le nouveau systeme a ete mis en oeuvre dans le cadre d'un essai sur le terrain en grandeur reelle qui a implique la construction d'un remblai technique compacte de 1,8 m de hauteur. A mesure que chaque couche de remblai etait placee et compactee, la pression verticale dans le sol et la contrainte verticale dans le sol etaient mesurees en continu. Pendant le processus de compactage vibratoire, les historiques de la pression verticale du sol et de la deformation verticale du sol ont ete saisis dans chaque couche. Les donnees recueillies ont permis de determiner la rigidite du remplissage pour les conditions statiques et dynamiques. Les resultats illustrent l'effet de la pression de confinement et du niveau de contrainte sur la rigidite du remplissage. La relation entre la pression de compactage et la profondeur est clairement definie. [Traduit par la Redaction] Mots-cles : mesure de la pression du sol, de la rigidite du sol, mesures dynamiques, remblai compacte.
Introduction The measurement of soil pressure is generally considered very difficult to perform in a reliable fashion. This reality is a result of two intersecting issues: (i) measurement of pressure [...]