Highway Research Record

VI. RESEARCH WORK DONE IN ACADEMIC INSTITUTIONS RELATED TO THESIS WORK
B. PAVEMENT ENGINEERING AND PAVING MATERIALS
Geotextiles in Temporary Roads Over Sandy Soils

Date of Start:August 2004
Indian Institute of Technology, Madras (R, C)

Scope and Objective
(i) To study the impact on the load bearing capacity of the soil by using nylon and coir as a Geotextile material on / below the     top surface of sandy soil.
(ii) To check the settlement and recovery of the soil at the varying depth by providing Geotextile layer.
(iii) To arrive at the desired depth, suitable for laying and recovery.
(iv) To compare the results with earlier studies on Geosynthetics.

Methodology
(i) Making laboratory arrangement for experimentation.
(ii) Preparing the desired samples of coir and nylon as Geotextile material for the experimentation.
(iii) To check the tensile properties of the material selected.
(iv) To perform standard ‘Plate Load Test’ for chosen material on the test bed of sand.
(v) To study the Load-settlement-recovery behaviour of all the selected reinforcing material(s) and analyze the results.
(vi) To identify suitable material(s) and check behaviour under repetitive loading.
(vii) Carry out further research work based on the laboratory work and field studies.

Findings and Conclusions

The experimental data obtained for the settlement and recovery from the plate load test has been amply analysed to infer the following findings:
(i) The use of nylon and coir as geo-reinforcement for soft sandy soil proved to be effective in the laboratory and can be     suitably used in lieu of Geosynthetic such as geonet/conveyer belts.
(ii) The settlement and recovery has reduced as the depth of embedment and the percentage of geo-reinforcement      increased.
(iii) The combination of geogrid at surface and nylon at 50 mm embedment undergoes minimum settlement even after higher      number of repetitions and hence is strongly recommended for the field trials for analyzing the effect of dynamic loading due      to the vehicular movement. During the field trials, the other combinations suggested above can also be tried out.
(iv) Use of geogrid at surface will help to avoid slip, which is likely to occur due to vehicular movement directly over nylon.
(v) The coir is found to give satisfactory settlement/recovery results and can be used effectively as geo-reinforcement.       However, keeping the resilience property of coir fiber in mind, it is expected to stabilize after slightly higher number of       repetitions.

Conclusions
(i) The use of nylon and coir as geo-reinforcement for sandy soil proved to be effective.
(ii) The settlement and recovery has reduced with the depth of embedment as the percentage of geo-reinforcement is       increased.
(iii) The combination of geogrid as surface and nylon at 50 mm embedment undergoes minimum settlement even after higher      number of repetitions and hence is strongly recommended for further field trials.
(iv) Use of geogrid at surface will help to avoid slip, which is likely to occur due to vehicular movement directly over sand.
(v) The coir is found to give satisfactory settlement/recovery results and can be used effectively as reinforcement. However,      keeping the resilience property of coir fibre in mind, it is expected to stabilize after higher number of repetions.
(vi) The cost of material under study is found to be cheaper as compared to other geosynthetic material.
(vii) Materials selected are economical, available in plenty and suit criteria for temporary tracks.