Behavior of Geotextile Reinforced Soil under Cyclic Loading

The vast potential of geotextiles for separation (reinforcement in pavements and rail roads is yet to be fully exploited in India, despite the initial successful trials. This is partly due to the lack of sufficient test data on the behavior under repetitive loading of indigenous geotextiles. This paper reports typical triaxial test results on reinforced and unreinforced specimens before and after cyclic loading. The reinforcement used is a needle punched polypropylene geotextile manufactured in India. The results reported include strength before and after cyclic loading (cyclic loading under both drained and undrained conditions), modulus of resilience and plastic strain. Limited test results on simulated rail road (pavement) specimens clearly reveal the absence of intermixing and improvement in strength and hence possible rutting

Effects of hospital facilities on patient outcomes after cancer surgery: an international, prospective, observational study

Background Early death after cancer surgery is higher in low-income and middle-income countries (LMICs) compared with in high-income countries, yet the impact of facility characteristics on early postoperative outcomes is unknown. The aim of this study was to examine the association between hospital infrastructure, resource availability, and processes on early outcomes after cancer surgery worldwide.Methods A multimethods analysis was performed as part of the GlobalSurg 3 study-a multicentre, international, prospective cohort study of patients who had surgery for breast, colorectal, or gastric cancer. The primary outcomes were 30-day mortality and 30-day major complication rates. Potentially beneficial hospital facilities were identified by variable selection to select those associated with 30-day mortality. Adjusted outcomes were determined using generalised estimating equations to account for patient characteristics and country-income group, with population stratification by hospital.Findings Between April 1, 2018, and April 23, 2019, facility-level data were collected for 9685 patients across 238 hospitals in 66 countries (91 hospitals in 20 high-income countries; 57 hospitals in 19 upper-middle-income countries; and 90 hospitals in 27 low-income to lower-middle-income countries). The availability of five hospital facilities was inversely associated with mortality: ultrasound, CT scanner, critical care unit, opioid analgesia, and oncologist. After adjustment for case-mix and country income group, hospitals with three or fewer of these facilities (62 hospitals, 1294 patients) had higher mortality compared with those with four or five (adjusted odds ratio [OR] 3.85 [95% CI 2.58-5.75]; p<0.0001), with excess mortality predominantly explained by a limited capacity to rescue following the development of major complications (63.0% vs 82.7%; OR 0.35 [0.23-0.53]; p<0.0001). Across LMICs, improvements in hospital facilities would prevent one to three deaths for every 100 patients undergoing surgery for cancer.Interpretation Hospitals with higher levels of infrastructure and resources have better outcomes after cancer surgery, independent of country income. Without urgent strengthening of hospital infrastructure and resources, the reductions in cancer-associated mortality associated with improved access will not be realised

Strategies for faster infrastructure development with Geosynthetics

Geosynthetics are planar, polymeric (synthetic or natural) materials used in contact with soil/rock and/or any other geotechnical material, for serving functions of Filtration, Drainage, Separation, Reinforcement, Protection, and Sealing, in civil engineering applications. There is a wide variety of products such as Woven geotextiles, non-woven geotextiles, uni-and bi-iaxial geogrids, geomembranes, various types of geocomposites, Prefabricated vertical drains, Rolled Erosion Control Products, geobags, geotubes etc., having potential applications in road structures-such as reinforced soil walls in bridge approaches, pavements; railway structures-bridge abutments, reinforced soil slopes; dams, canals and different ground improvement situations in soft soils. It is thus imperative that the performance of geosynthetic included structures depends on the nature of geotechnical materials, the loading conditions and the expected function the geosynthetic is expected to perform and is a complex geotechnical design issue. Though the application potential of the wide variety of geosynthetics is extremely high, the potential is yet to be tapped in our country, despite the fact that the major types are being indigenously manufactured, some to the International standards. The following briefly highlights the relevant issues. Lack of user Department Manuals and Specifications as well as construction guidelines. There are many grey areas, particularly in the railway and water resources sectors. In countries where high use is there, the manufacturers manufacture the product, as per clear Specifications which includes Manufacturing MARV values (MCA) and the user agency deals with Construction quality control (CQA). Importance of this is only now being realized in India. The existing Nodal agencies, primarily deal with Geotextiles (woven-non-woven) and woven geogrids and are not structured to deal with the entire spectrum of products or applications. Thereby, they serve primarily as Test Houses and rarely in a position to advise geotechnical performance. For a coordinated approach there is a need to establish a multi-disciplinary, Civil Engineering based National Geosynthetic Institute which does the job of not merely testing Geotextiles, but the entire range of geosynthetic products (because more than one product will need to be used in geosynthetic solution to a problem like landslides and pavements), but also involve in developing Design and Construction manuals in consonance with the user Departments/Ministries, Product certification and system certification (say of a new kind of geosynthetic reinforced soil wall, geotube solution for a coastal and river erosion control and natural fibre product range for embankment, river and hill slope erosion control problem). Over the years they may initiate relevant R&D. Similar mechanisms exist in USA, UK, Germany, France and Japan. If this is supported with Education and focused training programmes, it will go a long way in realizing the full potential of geosynthetics in faster and economic Infra projects as well as aid the manufacturing industry in value addition to their product range.by Rao G. Venkatapp

Geosynthetic reinforced soil Structures-A critical appraisal of design and construction

The awareness of geosynthetics in the country has begun around the year 1985. Soon after, the first Geosynthetic Reinforced Soil Retaining Wall has been built. Since then many hundreds of such structures have been constructed in the country in a variety of ground situations. After reviewing the basic design mechanism of reinforcing with geosynthetics, a critical appraisal of the prevailing design and construction practices in the country through the use of British, FHWA, NMCA Codes of Practice has been attempted. The importance of adequate geotechnical investigation and various aspects of construction, such as the type of reinforced fill soil to be used, and connection strength have been highlighted. Typical case histories have been presented.Rao G. Venkatapp

Behaviour of a Strip Footing on Compacted Pond Ash Reinforced with Coir Geotextiles

Pond ash, produced in huge quantities by thermal power plants, require large land area for disposal and causes environmental hazards. The pond ash can be effectively used as a fill material for low lying areas as site reclamations and in embankments. The low bearing capacity of pond ash fills can be improved by using coir geotextiles, as reinforcement which will be an eco-friendly approach. The effectiveness of horizontally placed coir geotextiles, as reinforcement in single and multiple layers, on the bearing capacity of compacted pond ash is investigated. In the present study, the bearing capacity behaviour of a strip footing on two pond ash samples reinforced with two types of woven coir geotextiles has been studied by load bearing tests in model tanks in the laboratory. The parameters varied during the tests were width of reinforcement, depth of the top reinforcement layer below the base of the footing and the number of geotextile layer. The improvement of ultimate bearing capacity was studied. The ultimate bearing capacity ratios were evaluated. A mathematical model based on the geometric parameters of the reinforcement, tensile properties of reinforcement and shear parameter of pond ash has been developed

Reinforced soil retaining structures for ravines

by Prajakta Jadhav and G. Venkatappa Ra

Geosynthetics: Recent developments

318-336A wide variety of geotextiles and related products available to civil engineers to solve a wide range of problems are briefly presented along with their functions and possible applications. The extensive work being carried out at the Indian Institute of Technology, Delhi, is highlighted. The testing required for hydraulic applications is presented in detail. The work carried out on design of needle-punched fabrics for hydraulic applications is described. A case study on use of edge drains for rural roads is presented. The work in progress on natural fibre geotextiles with jute and coir is included

Shear strength characteristics of saturated montmorillonite and kaolinite clays

This paper deals with the shear strength characteristics of saturated, remoulded, montmorillonite and Kaolinite clays as affected by changes in soil structure. The changes in soil structure were made by changes in initial moulding water content, stress history and type of cation and its concentration in the electrolyte system. Throughout the investigation, isotropically consolidated undrained tests with pore water pressure measurements were conducted. The experimental results show a definite cohesion intercept even for saturated normally consolidated clays, under certain conditions. The modified effective stress concept, which takes into consideration the electrical attractive and repulsive forces appears to explain satisfactorily the strength mechanism. The qualitative analysis of the test data brings out the dire need for quantitative evaluation of electrical attractive and repulsive forces in order that a realistic determination of strength parameters could be made. The manifestation of components of shear resistance has also been discussed briefly

Production method and characteristics of braided PVD

182-194The evolution of a new class of PVD having sheath of braided yarns encasing a large number of core yarns is described. The flexibility and simplicity of the production process leading to the possibility of controlled variation in dimensional, mechanical and hydraulic properties of the product have been highlighted. A limited comparative evaluation of some typical variants of this drain made of jute sheath and coir yarns as core with three other commercial PVDs has been reported. The hygroscopic nature of jute and coir plays a significant role in altering the thickness, pore size, permeability and discharge capacity of the drain in the wet state under confining pressure