Power Line Foundation Design Using the Pressuremeter

During the design phase of a 2000-towers electric power transmission line, a load test program was undertaken to evaluate the accuracy of new design methods for uplift and lateral capacity of drilled shafts. Seven uplift tests and six lateral load tests were performed in three different soil deposits: a medium clay, a very hard clay and a sand. The shafts were 2 ft in diameter and either 10 or 15 ft long. The pressuremeter test results are used together with existing methods to predict the behavior of the shafts

The borehole erosion test

Soil erosion is a major problem in civil engineering. It is involved in bridge scour, meander migration, levee and dam overtopping, internal erosion of earth dams, surface erosion of embankments, and cliff erosion. The best way to predict the erodibility of a soil is to measure it directly on a site specific basis by testing samples in the laboratory or by in-situ testing in the field. The borehole erosion test or BET is a new in-situ soil erosion test proposed to measure the erosion of the walls of a borehole while wet rotary drilling takes place. The increase in diameter of the borehole as a function of time and for a given flow velocity in the borehole is measured with borehole calipers. The result is a profile of soil erodibility as a function of depth. Tests in clay and in sand conducted at the National Geotechnical Experimentation Sites at Texas A&M University are presented

Relationship between soil erodibility and engineering properties

Different soils exhibit different erodibility (sand, clay) therefore erodibility is tied to soil properties. On the other hand, many researchers have attempted to develop such equations without much success. One problem is that erodibility is not a single number but a relationship between the erosion rate and the water velocity or the hydraulic shear stress. This erosion function is a curve and it is difficult to correlate a curve to soil properties. The main purpose of this study is to develop correlations between the elements of the erosion function (critical velocity, critical shear stress, slope of the erosion function) with elementary soil properties (plasticity index, mean grain size, unit weight, shear strength, and others). There are many tests to evaluate the erodibility of the soil in laboratory and in situ and to identify the erosion function (i.e. Jet Erosion Test, Erosion Function Apparatus, Hole Erosion Tests, etc.). This study deals with developing correlating equations between erodibility parameters obtained from many years of testing experience with Erosion Function Apparatus (EFA) and geotechnical properties of the soil

Load-settlement modelling of axially loaded drilled shafts using CPT-based recurrent neural networks

The design of pile foundations requires good estimation of the pile load-carrying capacity and settlement. Design for bearing capacity and design for settlement have been traditionally carried out separately. However, soil resistance and settlement are influenced by each other, and the design of pile foundations should thus consider the bearing capacity and settlement inseparably. This requires the full load–settlement response of piles to be well predicted. However, it is well known that the actual load–settlement response of pile foundations can be obtained only by load tests carried out in situ, which are expensive and time-consuming. In this paper, recurrent neural networks (RNNs) were used to develop a prediction model that can resemble the full load–settlement response of drilled shafts (bored piles) subjected to axial loading. The developed RNN model was calibrated and validated using several in situ full-scale pile load tests, as well as cone penetration test (CPT) data. The results indicate that the developed RNN model has the ability to reliably predict the load–settlement response of axially loaded drilled shafts and can thus be used by geotechnical engineers for routine design practice

Behavior of Piles and Pile Groups in Cohesionless Soils

DTFH61-82-C-0038In order to gain a better understanding of the behavior of piles in snad, an extensive search of the literature has been performed to collect data on instrumental piles driven in sand and tested under vertical loads. The load transfer characteristics of the piles were then analyzed without considering residual stresses. Wherever the data allowed it, the load transfer analysis was repeated after considering residual driving stresses. The results of this method as well as conventional and new in situ tests methods were then compared to actual load test results. Areas of critical need for further research are pointed out and recommendations are made for their implementation

Simultaneous determination of thermal conductivity, thermal diffusivity and specific heat in sI methane hydrate

This paper is not subject to U.S. copyright. The definitive version was published in Geophysical Journal International 169 (2007), 767–774, doi:10.1111/j.1365-246X.2007.03382.x.Thermal conductivity, thermal diffusivity and specific heat of sI methane hydrate were measured as functions of temperature and pressure using a needle probe technique. The temperature dependence was measured between −20°C and 17°C at 31.5 MPa. The pressure dependence was measured between 31.5 and 102 MPa at 14.4°C. Only weak temperature and pressure dependencies were observed. Methane hydrate thermal conductivity differs from that of water by less than 10 per cent, too little to provide a sensitive measure of hydrate content in water-saturated systems. Thermal diffusivity of methane hydrate is more than twice that of water, however, and its specific heat is about half that of water. Thus, when drilling into or through hydrate-rich sediment, heat from the borehole can raise the formation temperature more than 20 per cent faster than if the formation's pore space contains only water. Thermal properties of methane hydrate should be considered in safety and economic assessments of hydrate-bearing sediment.Gas Hydrate Project of the U.S. Geological Survey’s Coastal and Marine Geology Program, in addition to Department of Energy contract DE-AI21–92MC2921