Response of buried flexible pipe-soil system is studied, through numerical analysis, with respect to deflection and buckling in a spatially varying soil media. In numerical modeling procedure, soil parameters are modeled as two-dimensional non-Gaussian homogeneous random field using Cholesky decomposition technique. Numerical analysis is performed using random field theory combined with finite
difference numerical code FLAC 5.0 (2D). Monte Carlo simulations are performed to obtain the statistics,
i.e., mean and variance of deflection and circumferential (buckling) stresses of buried flexible pipe-soil
system in a spatially varying soil media. Results are compared and discussed in the light of available
analytical solutions as well as conventional numerical procedures in which soil parameters are considered
as uniformly constant. The statistical information obtained from Monte Carlo simulations is further utilized for the reliability analysis of buried flexible pipe-soil system with respect to deflection and buckling. The results of the reliability analysis clearly demonstrate the influence of extent of variation and spatial correlation structure of soil parameters on the performance assessment of buried flexible pipe-soil systems, which is not well captured in conventional procedures.
buried pipes; flexible; deflection; Monte Carlo; numerical; random; spatial.
Amit Srivastava and G.L. Sivakumar Babu: Department of Civil Engineering, Jaypee University of Engineering & Technology Guna, Madhya Pradesh, India - 473226
Amplification based on empirical relations is widely used for seismic microzonation of urban centers. Amplifications are used to represent the site effects of a particular soil column. Many empirical correlations are available to estimate the amplification of seismic waves. These correlations are based on the ratio of shear wave velocity of foundation/rock to soil velocity or 30 m equivalent shear wave velocity (Vs30) and are developed considering deep soil data. The aim of this work is to examine the
applicability of available amplification relations in the literature for shallow engineering bedrock sites by
carrying out site response studies. Shear wave velocity of thirteen sites having shallow engineering bedrock have been selected for the study. In these locations, the depth of engineering bedrock (> 760
amplification; site response; Vs30; earthquake; engineering bedrock.
P. Anbazhagan, Parihar Aditya and H.N. Rashmi: Department of Civil Engineering, Indian Institute of Science, Bangalore, India 5600012
This article describes laboratory research done on strength evaluations for stabilized samples made of tropical fibrous peat. The stabilizing agents used were ordinary Portland cement (OPC) as binding agent and blast furnace slag (BFS) as additive. Stabilized samples were tested for their strength through unconfined compressive strength (UCS) and California bearing ratio (CBR). Different dosage rates of OPC and BFS were used in trial and error experiments for the most effective combination for stabilized peat samples that were at their natural moisture content. Stabilized trial samples were air cured for 90 days. After detecting the most effective dosage rate in the trial samples, their values were used to prepare CBR samples at their optimum moisture content (OMC). CBR samples were then air cured from
1 to 90 days and tested under un-soaked and soaked conditions. The most effective dosage rate for the
stabilized peat samples was found to be close to when 75% for OPC and 25% of BFS per total weight of OPC, and BFS. As an example, if 11.25% OPC, and 3.75% BFS are mixed with peat and compacted at their OMC and air cured for 90 days, stabilized peat will have an increase in CBR of 0.8% to 45 % for un-soaked and 20% for soaked conditions.
fibrous peat; unconfined compressive strength; California bearing ratio; air curing; ordinary Portland cement; blast furnace slag.
Behzad Kalantari: Department of Civil Engineering, University of Hormozgan, Bandar Abbas, Iran
Waste fills resulting from coal mining should consist of large, free-draining sedimentary rocks fragments. The successful performance of these fills is related to the strength and durability of the individual rock fragments. When fills are made of shale fragments, some fragments will be durable and some will degrade into soil particles resulting from slaking and inter-particle point loads. The degraded material fills the voids between the intact fragments, and results in settlement. A laboratory program with point load and slake durability tests as well as thin section examination of sixty-eight shale samples from
the Appalachian region of the United States revealed that pore micro-geometry has a major influence on degradation. Under saturated and unsaturated conditions, the shales absorb water, and the air in their pores is compressed, breaking the shales. This breakage was more pronounced in shales with smooth pore boundaries and having a diameter equal to or smaller than 0.060 mm. If the pore walls were rough, the air-pressure breaking mechanism was not effective. However, pore roughness (measured by the fractal
dimension) had a detrimental effect on point load resistance. This study indicated that the optimum shales
to resist both slaking as well as point loads are those that have pores with a fractal dimension equal to
1.425 and a diameter equal to or smaller than 0.06 mm.
rock fills; shales; slaking; pores; capillarity; point load test; fractal; analysis.
Luis E. Vallejo: Department of Civil and Environmental Engineering, 949 Benedum Hall, University of Pittsburgh, Pittsburgh, PA 15261, USA
The consolidation behavior of Sri Lankan peaty clay is analyzed using an elasto-viscoplastic model. The model can describe the secondary compression behavior as a continuous process and it can also account for the effect of structural degradation on the consolidation analysis. The analysis takes into account all the main features involved in the process of peat consolidation, namely, finite strain, variable permeability, and the secondary compression. The material parameters required for the analysis and the procedures to evaluate them, using both standard laboratory and field tests, are explained. Initially, the model performance is assessed by comparing the predicted and the observed peat consolidation behavior
under laboratory conditions. The results indicate that the model is capable of predicting the observed creep settlements and the effect of layer thickness on the settlement analysis of peaty clay. Then, the model is applied to predict the consolidation behavior of peaty clay under different field conditions. In this context, firstly, the one-dimensional field consolidation of peaty clay, brought about by the construction of compacted earth fill, is predicted. Then, the two-dimensional peat foundation response upon embankment loading is simulated. A good agreement is seen in the comparison of the predicted results
with the field observations.
amorphous type peat; finite strain; structural degradation; elasto-viscoplastic consolidation
Asiri Karunawardena: National Building Research Organization, 99/1, Jawatte Road, Colombo 5, Sri Lanka
Fusao Oka and Sayuri Kimoto: Department of Civil and Earth Resources Engineering, Kyoto University, Kyotodaigaku-katsura 4, Nishikyo-ku, Kyoto 615-8540, Japan