Planar Reinforcements for Flexible Pavements

ase and subbase layers, forming a major portion of a pavement, are constructed using crushe d aggregates. In order to reduce the consumption of h uge quantities of aggregates in large-size projects, it is essential to adapt and utilize alternate materials and design me thods in building sustainable road ways. Reinforcing flexibl e pavements is one of the ways to improve the performance or to reduce the pavement thickness. Many researchers conducted exp eriments to quantify the benefit of reinforcing flexible pav ements in terms of traffic benefit ratio (TBR). In this study , Large Scale Model Experiments (LSME) are conducted to investigate the settlement behaviour of unpaved pavement system aga inst static loading. The design of reinforced unpaved ro ads is carried out using Giroud and Han method with reinfo rcement in the form of geogrids having aperture stability m odulus of 0.32 N-m/ 0 and 0.65 N-m/ 0 . The design of reinforced paved roads is carried out using AASHTO guidelines with th e selected TBR values equal to 3 and 6. From the LSME conducted on the unreinforced and reinforced unpave d pavement system, it is observed that inclusion of p lanar reinforcement in the form of geogrid or steel-wire- mesh within the aggregate layer resulted in load improvement fa ctor ranging from 1.1 to 1.9. Based on the design carrie d out using the proposed methods on paved and unpaved reinforce d roads, it is possible to reduce the pavement thickness fro m 20% to 70% depending on the type of geogrid and subgrade s trength

Hox Genes Regulate Muscle Founder Cell Pattern Autonomously and Regulate Morphogenesis Through Motor Neurons

The differentiation of myoblasts to form functional muscle fibers is a consequence of interactions between the mesoderm and ectoderm. The authors examine the role of segment identity in directing these interactions by studying the role of Hox genes in patterning adult muscles in Drosophila. Using the `four-winged fly' to remove Ultrabithorax function in the developing adult, the authors alter the identity of the ectoderm of the third thoracic segment towards the second and show that this is sufficient to inductively alter most properties of the mesoderm—myoblast number, molecular diversity, and migration pattern—to that of the second thoracic segment. Not all aspects of myogenesis are determined by the segment identity of the ectoderm. The autonomous identity of the mesoderm is important for choosing muscle founder cells in the correct segmental pattern. The authors show this by removal of the function of Antennapedia, the Hox gene expressed in the mesoderm of the third thoracic segment. This results in the transformation of founder cells to a second-thoracic pattern. The authors also report a role for the nervous system in later aspects of muscle morphogenesis by specifically altering Ultrabithorax gene expression in motor neurons. Thus, ectoderm and mesoderm segment identities collaborate to direct muscle differentiation by affecting distinct aspects of the process

Load-Settlement Response of Square Footing on Geogrid Reinforced Layered Granular Beds

Experimental studies were carried out to obtain the load-settlement response of a model square footing resting on unreinforced and reinforced granular beds. The response was obtained for two cases: (a) geogrid-reinforced sand layer, and (b) geogrid-reinforced layered system consisting of aggregate layer overlying a sand layer. The parameters considered in the experimental study include the thickness of the aggregate layer, the depth of geogrid reinforcement placed in sand layer and in aggregate layer, width of the reinforcement, and relative density of bed. Plate vibrator was used to compact uniform sand beds to relative densities equal to 50 % and 70 % inside large-size test chamber of dimensions equal to 1 m × 1 m × 1 m (in length, in width, and in depth). Load was applied on square footing using a 100 kN capacity actuator in displacement-controlled mode, and the improvement in the load carrying capacity of the footing resting on reinforced sand layer and layered system was quantified in terms of load improvement factors. In addition, the optimum embedment depth and width of reinforcements were proposed for various cases considered in the study. The optimum depth of reinforcement for the case of aggregate layer overlying sand layer decreased to 0.30 times the width of the footing from 0.45 times the width of the footing for sand only case

Settlement Analysis of Circular Footings on Layered Soil Systems

Many studies are available on the settlement analysis of footings on a homogeneous soil deposit underlain by a rigid base. However, the soil profile is seldom homogenous and typically a layered soil system is encountered in practice. The present study deals with the settlement profiles of soil underneath a circular footing of radius equal to a, and resting on a finite two-layered soil system with thicknesses equal to H1 and H2. The deformation moduli and Poisson’s ratios of the two layers are E1, υ1, and E2, υ2. The settlement profiles are proposed for varying H1/a and H2/a ratios (H1/a= 0.2, 0.5, 1, 2, 4 and 6, and H2/a= 1, 2, 4 and 6). The moduli ratio E1/E2is varied as 0.01, 0.05, 0.1, 0.5, 1, 2, 5 and 20. The extent of settlement due to load is also proposed from the surface settlement profile which can help in determining the influence of a footing on the neighboring footing or structure. The analysis is carried out using PLAXIS 2D vAE. In addition, the settlement influence factors are proposed for the above mentioned ratios to estimate the maximum settlement of the footing on a layered system. The results are also compared with the settlement measured in a building on a layered system in Adelaide, Southern Australia, and the results are found to be comparable

Finite Element Modeling of Ground - Structure Interaction Considering Non-Linear Response of the Ground

Response of the ground on which the structure rests will have a bearing on the distribution of forces in the structural members. Conventional method s of structural analysis and design a ssume often fixed bases for various loading conditions. A realistic analysis and design procedure should includ e actual support flexibility, no nlinear and heterogeneous nature of the soil together with nonlinear soil-structure in teraction effects. Such an analysis would resu lt in overall stiffne ss of the soil-foundation-structure system , realistic to the existing conditions. This work focuses on the computational modeling of ground-structure interaction usi ng finite element package ANSYS. To demonstrate the behavior of structure while considering actual nature of ground response , a simple portal frame is analyzed. Portal frame is modeled as linear elastic, whereas the ground is modeled as both linear elastic and non-linear elastic-plastic behavior. The study gives insight into variation of displacement of portal frame while considering linear and non-linear behavior of ground

Behavior of Granular Pile and Granular Piled Raft

Granular pile, also popularly known as stone column, is an economical and efficient ground improvement technique to treat variety of soils. Depending on loading, geometry and spacing pattern, granular pile may fail individually or as a group. Bulging failure of granular pile is the most common failure criterion among the possible failure mechanisms – punching failure, shear failure and bulging failure. In this study, Finite Element analyses have been performed using commercially available software PLAXIS 2D to understand the bulging and the load-settlement behavior of both single floating granular pile and granular piled raft embedded in a soft clay deposit. Elastic-perfectly plastic response (Mohr-Coulomb criterion) is used to model both the granular pile and the soft clay. Parametric study is carried out by varying the properties of clay and granular pile to understand and quantify (a) the bulging along the depth of the pile with and without raft, and (b) the load-carrying capacity of granular pile and piled raft. Critical length of granular pile is also proposed for the cases considered in the study

Effect of Dilatancy Angle on Bearing Capacity

In Mohr-Coulomb failure criterion, the angle of shearing resistance of soil is assumed to be constant along the slip plane. However, over the second half of the last century, it is well recognized that the dilatancy angle influences the shear strength of sand. Many researchers have proposed correlations between the angle of shearing resistance at peak state in terms of intrinsic soil variables and soil state variables. Studies on the effect of dilatancy angle of soil, ψ, on the load-settlement response of a strip footing are available in the literature. However, in most of these studies, ψ equal to zero or equal to angle of shearing resistance of soil, is assumed, and only limited studies are available to predict the load-settlement response of strip footing when the dilatancy angle of sand lies between zero and In the present study, the effect of dilatancy angle of sand on the loadsettlement response of a rigid strip footing resting on sand and on the formation of slip planes is studied by varying the dilatancy angle ranging from zero to the angle of shearing resistance of soil (i.e., ψ =0 to

Odontogenic Fibromyxoma of Maxilla: A Case Report

Odontogenic fibromyxoma (OM) is a rare locally invasive, non metastasizing benign neoplasm found exclusively in the jaws. It commonly occurs in the second and third decade,and the mandible is involved more commonly than the maxilla. The lesion often grows without symptoms and presents as a painless swelling. The radiographic features are variable so the diagnosis is not easy in many cases. It posesa diagnostic and therapeutic challenge due to its morphology and biological behaviour. A caseo f OM of the maxilla with unusual radiographic and histological features is described in a 27 year old female

Settlement Due to Circular Load on Finite Two- Layered Soil System

Structures are commonly founded on layered soil deposits. Many instances are there where the soil profile consisted of two-layer soil deposit, underlain by a rock stratum. So in this thesis, finite two-layered soil profile overlying a stiff soil deposit is considered. Top layer of the soil is loose sand and bottom layer of the soil is sandy gravel considered and vice versa. Elastic settlements due to a flexible and rigid circular load on a two-layer soil system without reinforcement and with incorporating reinforcement overlying a rock stratum or a stiff soil deposit are estimated by design charts and tables. As soil behavior is not elastic in nature, so approximating the soil behavior in general by elasto-plastic behavior, it is obtained by Mohr-Coulomb model in Plaxis 2D. Plastic settlements due to a flexible and rigid circular load on a two-layer soil system overlying a rock stratum or a stiff soil deposit are estimated by design charts and tables

Stress Distribution on Bridge Abutment due to Live Loads

Stress distribution on the bridge abutment plays a key role in the design of bridge abutments. Lateral stress on the abutment will be due to backfill and live loads (wheel loads). Lateral stress due to backfill can be determined by classical earth pressure theories that are well documented in the literature. However, the effect of lateral stress distribution due to live loads/wheel loads are typically assumed as an equivalent uniformly distributed load of additional height of surcharge of backfill over the surface of the backfill. IRC recommendation of 1.2m height of surcharge is based on engineering judgment and experience. This study aims to predict the lateral stress on bridge abutment more closely to the actual values. A model was developed using finite element package PLAXIS and the lateral stress distribution on abutment for various lanes are obtained. In the present study, abutment-soil system was modeled considering two cases- (a) two-layered system with a granular base layer/approach slab resting on the embankment fill material, and (b) three-layered system with an approach slab over the granular base layer resting on the embankment fill material. The equivalent height of surcharge is proposed for various moduli ratio of the pavement layers and for different lane widths (corresponding to one, two, three, four and five lanes). It is determined that the equivalent height of surcharge for case(a) two-layered system is in the range of 0.7m-1.3m and for case(b) three-layered system with an approach slab is in the range of 0.5m-0.9m