| In conjunction with the Olmsted Locks and Dam project, one of the largest civil engineering projects currently under construction in the United States, a comprehensive pile testing program was performed. From these pile tests, a soil stratum known as the McNairy formation was discovered to have high in-situ horizontal stress. The study area is located in the geologically and seismotectonically complex area of the upper Mississippi Embayment. The backcalculation of K0, the ratio of horizontal effective stress to vertical effective stress (σ′h/σ′ v), from static pile load tests defined the magnitude of horizontal effective stress in the range from 2 to greater than 10. The K0 profile was then verified by measurements with a self-boring pressuremeter. This study presents a new method for the estimation of K0 that utilizes shear wave velocity measurements made in the field by cross-hole testing and laboratory measurements using bender elements. The method was successful, showing good agreement with K0 profiles determined from the pile load tests and self-boring pressuremeter. The source of the high in-situ stress is thought to be of tectonic origin and significant evidence to support this theory is presented. |
