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Prediction Equations to Determine Induced Force on Reinforcing Elements Due to Laterally Loaded Piles Behind MSE Wall and Lateral Load Test on Dense SandGarcia Montesinos, Pedro David 17 December 2021 (has links)
Researchers performed 35 full-scale lateral load tests on piles driven within the reinforcement zone of a mechanically stabilized earth wall (MSE wall). Data defining the induced tensile force on the reinforcements during lateral pile loading was used to develop multi-linear regression equations to predict the induced tensile force. Equations were developed by previous researchers that did not consider the diameter of the pile, the fixed head condition, relative compaction, or cyclic loading. The purpose of this research was to include this tensile force data and develop prediction equations that considered these variables. Additionally, a full-scale lateral load test was performed for a 24-inch diameter pipe pile loaded against a 20-inch width square pile. The test piles were instrumented using load cells, string potentiometers, LVDTs, strain gauges and hybrid pressure sensors. The lateral load tests were used to evaluate the ability of finite difference (LPILE) and finite element (PLAXIS3D) models to compute results comparable to the measured results. The results of this analysis showed that the diameter of the pile is a statistically significant variable for the prediction of induced tensile force, and the induced tensile force is lower for piles with larger diameter. Fixed head conditions have no effect on the prediction of induced tensile force. Cyclic loading had minimal impact on the prediction of induced tensile force, but relative compaction did have an important statistical significance. Therefore, prediction equations for induced tensile force in welded wire were developed for relative compaction less than 95 percent and relative compaction greater or equal than 95 percent. A general prediction equation (Eq. 3-4) was developed for ribbed-strip reinforcements that included the effect of pile diameter and larger head loads. With 1058 data points, this equation has an R2 value of 0.72. A general prediction equation (Eq. 3-9) was also developed for welded-wire reinforcements that included data from cyclic and static loading, fixed and free head conditions, and relative compaction for 12-inch wide piles with a higher range of pile head loads. This equation based on 2070 data points has an R2 value of 0.72. The prediction equations developed based on all the available data are superior to equations developed based on the original set of field tests. The finite element models produced results with good agreement with pipe pile measurements while the finite difference model showed better agreement with the square pile measurements. However, for the denser backfills involved, back-calculated soil properties were much higher than would be predicted based on API correlations. The API equations are not well-calibrated for dense granular backfills.
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Effects of Environmental Factors on Construction of Soil-Cement Pavement LayersMichener, John E. 24 September 2008 (has links)
The specific objectives of this research were to quantify the effects of certain environmental factors on the relative strength loss of soil-cement subjected to compaction delay and to develop a numerical tool that can be easily used by engineers and contractors for determining a maximum compaction delay time for a given project. These objectives were addressed through extensive laboratory work and statistical analyses. The laboratory work involved testing an aggregate base material and a subgrade soil, each treated with two levels of cement. Environmental factors included in the experimentation were wind speed, temperature, and relative humidity, and three levels of each were evaluated in combination with varying compaction delay times. The primary response variables in this research were relative compaction and relative strength. The findings indicate that relative strength is sensitive to variability among the selected independent variables within the ranges investigated in this research, while relative compaction is not. Inferring relative strength from relative compaction is therefore not a reliable approach on soil-cement projects. Consistent with theory, higher wind speed, higher air temperature, lower relative humidity, and higher compaction delay time generally result in lower relative strength. With the nomographs developed in this research, the maximum delay time permitted for compaction of either a base or subgrade material similar to those tested in this research can be determined. Knowing in advance how much time is available for working the soil-cement will help contractors schedule their activities more appropriately and ultimately produce higher quality roads. When acceptable compaction delays are not obtainable due to adverse environmental conditions, a contractor may consider using set retarder, mixing at water contents above OMC, or constructing at night as possible solutions for achieving target relative strength values.
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