Pore Water Pressure

Previous case histories have shown that soil liquefaction severely damaged many structures supported on pile foundations during earthquakes. As a result, evaluating the potential for instability is an important consideration for the safe and resistant design of deep foundation against earthquakes. In this study, the liquefaction susceptibility of saturated sand interacting by single concrete pile was simulated by means of finite difference method. A nonlinear effective stress analysis was used to evaluate soil liquefaction, and the soil-pile interaction was considered using interface elements. The parameter Ru was defined as the pore water pressure ratio to investigate liquefaction in the soil mass during time. A set of numerical models were carried out by three types of soil mass with various condensation (loose, semi-dense and dense) under three ground motion with different predominant frequencies and peak accelerations. The effect of these parameters was studied using excess pore...

This paper presents the observations of cone penetration testing (CPT), in situ vane shear testing and undrained triaxial testing of underconsolidated marine clay in the Craney Island Dredged Material Management Area (CIDMMA), Norfolk, VA. Comparison of vane shear measurements, taken during 1981–1983, to CPT measurements, taken during 1993, indicates a change in undrained shear strength. Both the vane shear and cone penetration resistances are lowest at the mid-heights of the clay layers and the excess pore water pressures are highest at the mid-height of the clay layers, indicating that the clay layer is underconsolidated.

Edge-of-field buffers are a core agricultural conservation practice, and installed along the stream are a proven technology to reduce sediment loadings from both hillslope and channel bank. This paper presents ongoing research to integrate the computer models CONCEPTS and REMM, which were developed to simulate stream channel morphology and riparian ecosystem function. The integrated model has been used to study the effectiveness of hypothetical woody and herbaceous riparian buffers in controlling streambank stability of an incised stream in Mississippi. Riparian vegetation controls streambank stability through pore-water pressure (i.e., soil water content) and root-reinforcement of the soil. The capability of the model to predict spatial and temporal variations of pore-water pressure in a streambank was tested against field data collected at Goodwin Creek, Mississippi. Model results showed that pore-water pressures are accurately predicted in the upper part of the streambank, away f...

Previous case histories have shown that soil liquefaction severely damaged many structures supported on pile foundations during earthquakes. As a result, evaluating the potential for instability is an important consideration for the safe and resistant design of deep foundation against earthquakes. In this study, the liquefaction susceptibility of saturated sand interacting by single concrete pile was simulated by means of finite difference method. A nonlinear effective stress analysis was used to evaluate soil liquefaction, and the soil-pile interaction was considered using interface elements. The parameter Ru was defined as the pore water pressure ratio to investigate liquefaction in the soil mass during time. A set of numerical models were carried out by three types of soil mass with various condensation (loose, semi-dense and dense) under three ground motion with different predominant frequencies and peak accelerations. The effect of these parameters was studied using excess pore pressure, lateral movement and settlement time histories. It was found that the pile can affect the liquefaction susceptibility of soil by comparing the near pile and free field responses. However, for various soil and earthquake characteristics, it was found that the depth of soil liquefaction and triggering, varies.

The behavior of piles in seismic areas is significantly affected if the soil liquefies. The strength of the soil and its stiffness decrease due to the increase in pore water pressure. The observed pile damage during earthquakes has provided an insight into the mechanism of soil-pile interaction in liquefying soils. The piles in liquefied soil may undergo large lateral displacements and my fail due to bending or buckling. The paper discusses the observed performance of piles in liquefying soils and the suggested methods for their design.