The shear strength (S u) of soils is one of the most widely used parameters for designing structures safely, where Su is found with the unconfined compression test (UCS). Although UCS can be acquired by performing uniaxial compression test it would be extremely helpful to predict the UCS without performing any compression test, namely, using computational methods considering different parameters of soils such as consistency limits, fine grain ratio, liquidity index, and void ratio. The goal of present work is predicting UCS taking into account these soil parameters with the aid of developed Adaptive Neuro-Fuzzy Inference System (ANFIS) model and the Multiple Linear Regression (MLR) analyses. On the other hand, the effect of the size of the training set of designed models on the results is examined, also. For this aim, four different models composed of different training and test set ratios have been constructed and analyzed using ANFIS and MLR. It is concluded that UCS can be predicted using MLR analysis and ANFIS model with best 0.76 and 0.91 values of determination coefficient (R 2) around the x = y line respectively, and the effect of the size of the training set of models on ANFIS is more pronounced than MLR models.
The primary consolidation may take long time due to the low permeability of clay soils in such cases soil improvement may be required to shorten the consolidation time, increase shear strength, and therefore bearing capacity. Preloading is one of the commonly used methods to consolidate soils before actual load and to strengthen weak compressible soils. In cases with time problems, the use of prefabricated vertical drains (PVD) with pre-loading shortens the drainage path and reduces the consolidation time by taking advantage of the horizontal permeability of the soils is generally higher. In this study, an embankment constructed at different load rates with constant accelerates and analyzes were performed for the non-drained and drained conditions of clay soils with PVDs are in 2m, 1m, and 0.5m intervals. In this way, the effect of load rate and PVD usage on consolidation settlement and excess pore pressures in underlying low permeable clayey soil was investigated.
Shortening of the consolidation time of road fills built on soft soils is an important problem and design factor. In this study, the consolidation time and dissipation of excess pore pressures were examined for both natural and vertical prefabricated drains improved soft soil by finite element analyses. Analyses were done with Plaxis 2D software which is used for two dimensional analyses of deformation and stability problems in geotechnical engineering.
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