GEOSYNTHETICS ENGINEERING: IN THEORY AND PRACTICE

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2 GEOSYNTHETICS ENGINEERING: IN THEORY AND PRACTICE Prof. J. N. Mandal Department of civil engineering, IIT Bombay, Powai, Mumbai , India. Tel

3 Module-5 LECTURE- 25 GEOSYNTHETICS IN PAVEMENTS

4 RECAP of previous lecture.. Excel program Design methods for geosynthetic reinforced flexible airfield pavements Barenberg design method Federal Aviation Administration (FAA) design method and its modification Combinations of Barenberg and modified FAA method Pavement overlay Modes of crack propagation Geosynthetics for pavement overlay Tack coat Construction of overlay

5 Open Graded Asphalt Concrete for Mitigation of Reflection Cracking Because of reflection cracking, old distressed plain cement concrete as well as flexible pavement is rehabilitated year after year conventionally by laying asphalt concrete overlay. Reflection cracking is defined as the fractures in a newly laid overlay that reflects the crack or joint pattern in the underlying layer of old road bases. Reflection cracking in asphalt concrete overlay

6 Photograph of the Asphalt Concrete Slab Fatigue Testing Equipment (Bhosale and Mandal, 2006)

7 Designed aggregate gradations for open graded asphalt concrete

8 Geosynthetic reinforcing materials e.g. PET Fibers, Polyester Woven Geotextile, Glass Grid and Polyester Geogrid were used in the experimental work. Tensile strength: PET fiber 509 kpa to 755 kpa Polyester woven geotextile kn/m Glass grid 50 kn/m Polyester geogrid 70 kn/m Elongation at break for polyester woven geotextile, glass grid and polyester geogrid were 33%, 5% and 19% respectively. Though tensile strength of glass grid is less, its stiffness is three times more than the polyester geogrid.

9 For geosynthetic reinforced open graded asphalt concrete (OGAC) overlay, the base course of OGAC is reinforced by, - mixing 0.5% PET Fibers, or mm x 400 mm reinforcement interlayer of polyester woven geotextile or glass-grid or polyester geogrid is placed between the base course of OGAC and surface course of bituminous concrete (BC).

10 Designation and details of test slabs Test Slab Testing Type of Asphalt Concrete Base Course Designation Mode DBM-O O Unreinforced Dense Bituminous Macadam (DBM). DBM-M M Unreinforced Dense Bituminous Macadam (DBM). OG-O O Unreinforced Open Graded (OG) Asphalt Concrete. OG-M M Unreinforced Open Graded (OG) Asphalt Concrete. PetF-O O PET Fiber (PetF) reinforced OGAC. PetF-M M PET Fiber (PetF) reinforced OGAC. Gtx-O O Polyester Woven geotextile (Gtx) reinforced OGAC. Gtx-M M Polyester Woven geotextile (Gtx) reinforced OGAC. GlGrid-O O Glass Grid (GlGrid) reinforced OGAC. GlGrid-M M Glass Grid (GlGrid) reinforced OGAC. Geogrid-O O Polyester Geogrid (Geogrid) reinforced OGAC. Geogrid-M M Polyester Geogrid (Geogrid) reinforced OGAC. Note: O = Opening Mode, M = Mixed Mode, OGAC = Open Graded Asphalt Concrete.

11 Unreinforced dense bituminous macadam or open graded asphalt concrete overlay test slab Reinforced open graded asphalt concrete overlay test slab

12 Loading waveform in purely opening mode of displacement; and the modes of displacements

13 Percentage variation in base isolation effectiveness factor of some critical parameters due to differential deflection Overlay Test Slab Designation Base Isolation Effectiveness Factor (BIEF) Percentage Variation in BIEF O M DBM OG PetF Gtx GlGrid Geogrid Note: O = Opening Mode, M = Mixed Mode, + increase in BIEF, - decrease in BIEF

14 Percentage variation in fabric effectiveness factors of some critical parameters due to differential deflection Overlay Test Slab Designation Fabric Effectiveness Factor (FEF) O M Percentage Variation in FEF OG PetF Gtx GlGrid Geogrid Note: O = Opening Mode, M = Mixed Mode, + increase in FEF, - decrease in FEF

15 Discussion (1) Differential deflection of 5 mm with zero load efficiency factors in mixed mode of displacement is found to cause large cumulative decay of engineering parameters viz. tensile force, stiffness modulus and shear modulus. (2) The conventional overlay with a base course of dense bituminous macadam and surface course of bituminous concrete does not arrest the crack propagation. (3) Since unreinforced OGAC overlay shows BIEF of in mixed mode of displacement, it is confirmed that it works as the crack relief layer.

16 (4) PET Fiber reinforcement shows base isolation effectiveness factor of which is less than that of unreinforced open graded asphalt concrete overlay and hence, does not improve base isolation function of open graded asphalt concrete. Also the fabric effectiveness factor for PET Fiber is which is less than 1 and therefore, does not provide reinforcement benefit. Hence, 0.5% PET Fibers is not a suitable quantity for 50 mm thick open graded asphalt concrete base course.

17 (5) The polyester woven geotextile reinforced open graded asphalt concrete overlay shows the largest fabric effectiveness factor of and the largest base isolation effectiveness factor of in opening mode of displacement. Hence it is the best choice in purely opening mode of displacement. However, under mix mode of displacement having 5 mm differential deflection with zero load efficiency factors, it shows the least base isolation effectiveness factor of and the least fabric effectiveness factor of confirming that it is not suitable under mixed mode.

18 (6) The glass grid reinforced open graded asphalt concrete overlay shows the highest base isolation effectiveness factor of and also the highest fabric effectiveness factor of under mixed mode of displacement. Thus it is the best choice in mixed mode of displacement. (7) The polyester geogrid reinforced open graded asphalt concrete overlay shows the base isolation effectiveness factor of and fabric effectiveness factor of under mixed mode of displacement. It is the second best choice in mixed mode of displacement. Though polyester geogrid has 1.4 times higher tensile strength than that of glass grid, its stiffness is 1/3 rd of that of glass grid. This particular aspect confirms that stiffness of fabric played a vital role in reinforcing the overlay during differential deflection in mixed mode of displacement.

19 GEOSYNTHETICS IN RAILROADS

20 Geosynthetics can be used beneath or within the stone ballast and/ or sub ballast layers for the construction of new railway track or rehabilitation. Geotextiles, geogrids, geocells and geocomposites are commonly used. Geosynthetic materials can be used for multifunction: Separation, Filtration, Drainage, Reinforcement The primary function of geosynthetic is to separate the stone ballasts and subgrade soil.

21 Due to dynamic wheel load of railways, pore water pressure develops in the subgrade soil. It is required to dissipate the pore water pressure rapidly. Geosynthetics laid over the subgrade soil can fulfill the required drainage and filtration function. It is required to check adequate permeability, soil retention, resistant to clogging and long term flow criterion of the geosynthetic before its practical application.

22 Geocomposite material can act for both separation and filtration. Upper side of the geotextile in geocomposite reinforcement requires high abrasion resistance because it interacts with the ballast stone. Similarly, lower side of the geotextile in geocomposite reinforcement requires adequate filtration because it interacts with the very fine subgrade soil.

23 Geocomposite in railway track for filtration

24 Typical drainage system for railway track (Jay, 2002)

25 Geosynthetic reinforcement also provides lateral confinement. It is very flexible and deforms due to the dynamic load over stone ballast through railroad tie. Therefore, it does not easily fail or form the slip surface. Friction also mobilizes between stone ballasts and geosynthetic. It can keep the ballast stones in proper place. As reinforcement, geosynthetic can increase the load bearing capacity by better stress distribution as well as reduce the settlement. The issue is about the depth of placement of geosynthetic below the railroad tie. High dynamic load imparts acceleration on the stone ballast and diminishes with depth of the ballast.

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27 Raymond (1982) reported that damage takes place at a depth of 200 mm. The minimum depth for placement of geosynthetic is 350 mm plus 50 mm track settlement, i.e. at a depth of 400 mm. Check burst strength, abrasion resistance, grab tensile strength, drop cone test (impact) and puncture resistance of geosynthetic. Raymond (1982) recommended the resin-dipped nonwoven needle-punched very stiff geosynthetic (1000 g/m 2 ) for railroad project. It can perform both separation and drainage functions. The needle-punched geosynthetic was used for the rehabilitation of Canadian railway track.

28 The combination of geotextile and geogrid was successfully used for railroad track rehabilitation in USA. Geotextile acts for separation and filtration. It prevents contamination of the ballast and releases the quickly built up pore water pressure. Geogrid acts as very good reinforcement. There is a very good interlocking/ bonding/ confining effect between the ballasts and geogrid. As a result, it can resist lateral and vertical movement of the ballasts as well as increase the bearing capacity of subgrade soil. The geocomposite material reduces maintenance costs as well as enhances the life of railroad track.

29 Railway track with drainage system using geogrid and geotextile Railway track in hilly area with proper drainage system, erosion control and stabilized slope with cellular reinforcement

30 Railway track in hilly area with proper geosynthetic drainage system and stabilized slope with cellular reinforcement or wraparound geotextile

31 Railway track in hilly area with proper geosynthetic drainage system and erosion control in slopes with cellular reinforcement or geotextile mat

32 Combination of reinforced earth wall (REW) and reinforced soil slope (RSS) for railways and roads

33 Combination of pile foundation and geogrid reinforced embankment for railways

34 Land reclamation using PVD in railway or railway parking Construction of railway embankments using wraparound geogrid

35 GEOCOMPOSITE IN RAILWAY TRACK Puncture failure in geotextile due to installation of ballast Abrasion failure of geotextile due to dynamic loads Required a specific abrasion resistance geotextile on the top side tightly fixed with a non-woven geotextile Geocomposite to prevent abrasion and puncture failure

36 GEOCOMPOSITE IN RAILWAY TUNNEL The needle punched nonwoven geotextile acts for drainage to drain out the rain water. Geomembrane acts as an impermeable barrier to prevent the water from passing through it to the railway track. If there is any angular ballast stone, geotextile can act as a cushion.

37 GEOSYNTHETICS IN RAIL ROAD FOUNDATION Reinforced aggregate raft can be used as railroad foundation to reduce and redistribute the load on soft, low strength subgrade soil. It also minimizes the depth of excavation. Multilayer of geogrid with compacted aggregates to stabilize the railway foundation bed

38 Mud Pumping Under Railway Track Rail Ballast Sleeper s Pumping action Sub-base Void created as stones move apart under wheel load on sleeper Mud moves in to fill the void as wheel load passes

39 (a) At the time the rail wheel is over the sleeper, load acts downwards on the sub base. As a result, stones move apart both directions and create void. (b) When the wheel passes one sleeper to the other, later sleeper moves upward due to pumping action. As a result, the stones will try to close each-other and mud pumping occurs in upward direction to fill the voids.

40 Water stagnation in railway track due to mud pumping Control the mud pumping is difficult and prone to accident. Mud pumping can be prevented using geosynthetics.

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42 REINFORCED SLEEPER BED IN RAILWAYS Tubular woven polyester bags are filled with rounded gravel or locally available suitable materials at higher degree of compaction and tied with the railway sleepers by polyester straps. It can act as a reinforced sleeper bed. Polyester bag filled with rounded gravel in European railway (After Van Zanten, 1986, Van Santvoort and Troost,1986)

43 The sleeper may be made of concrete, wood and steel. The bag can be made little bit flatter and anchored firmly with the sleeper. The bag can withstand heavy load without breaking or splintering of the filling materials. Deformation of the bag is relatively less. Strength of geotextile for the bag is 100 kn/m and 120 kn/m for the strap at a peak strain of 12 %. The design strength is calculated at 5% strain considering factor of safety = 4. (Van Zanten, 1986) Vibration due to passing of trains can be reduced. The maintenance cost will be reduced.

44 GEOSYNTHETICS FOR ROADWAY REPAIRING Distressed pavement

45 Repair using geotextile and geogrid

46 Repair using geogrid geocell and geotextile

47 Repair using geofoam and geogrid

48 GEOSYNTHETICS FOR ROADWAY EXTENSION Geofoam geocells for roadway widening at both sides of the existing roadway

49 Geofoam geocells for roadway widening at one side of the existing roadway

50 Geofoam blocks for roadway widening at both sides of the existing roadway

51 Geofoam blocks for roadway widening at one side of the existing roadway

52 Correct choice, specifications and installation of geosynthetics Improvement in the performance of roadways, runways and railways Cost-effective solution SUMMARY Increase life span of structures Reduce the maintenance costs

53 STABILIZATION OF PAVEMENT USING NANO MATERIAL Compaction Test Different percentages of cement and Nano zinc oxide were mixed with Powai soil and compaction tests have been carried out. Test results indicated reduction in maximum dry density with increased optimum moisture content while compared to the only soil.

54 Case-1= Soil + 2% cement + 0.1% Nano zinc oxide Case-2= Soil + 4% cement + 0.2% Nano zinc oxide Case-3= Soil + 6% cement + 0.3% Nano zinc oxide Compaction curves for Powai soil and Soil mix with different percentages of cement and Nano zinc oxide

55 California Bearing Ratio (CBR) Test California bearing ratio (CBR) tests were carried out as per IS 2720 (Part 16) 1987 on only Powai soil and soil mixed with cement and Nano zinc oxide at different proportions. California Bearing Ratio (CBR) values Test Details Soil Soil+ 2%cement+ 0.1% Nano zinc oxide Soil+ 4%cement + 0.1% Nano zinc oxide Soil+ 6%cement+ 0.1% Nano zinc oxide Penetration (mm) CBR

56 Unconfined Compressive Strength Test Test conditi ons 7 days Curing 14 days Curing Soil (kg/cm 2 ) Soil+ 2%Cem.+ 0.3% Nano zinc oxide (kg/cm 2 ) Soil+ 4%Cem.+ 0.3% Nano zinc oxide (kg/cm 2 ) Soil+ 6%Cem.+ 0.3% Nano zinc oxide (kg/cm 2 ) days Curing

57 Pavement construction with alternative materials As the quality of aggregates is now becoming scarce due to legal restrictions and environmental problems, alternative large scale locally available material can be used for the construction of flexible pavements. Recycling of reclaimed asphalt pavement (RAP ) can be used as an alternative material for pavement design. The gradation of RAP can be mixed with new suitable materials and adhesive to produce an alternative new materials which can be used for the base/sub-base and /or as a new binder materials. The cost of bitumen is also increasing enormously. The use of RAP can reduce the cost of highway construction.

58 Major quantity of aggregate is required for the construction of granular base and subbase of flexible pavement. As per Indian Road Congress (IRC) guidelines, thickness of the base course is about 250 mm and thickness of the sub base is about 200 mm-300 mm based on traffic requirement and subgrade strength. Using appropriate geosynthetics, it is possible to reduce the thickness of granular base and sub base for similar or even better performances. In addition, reclaimed asphalt pavement (RAP) and reclaimed concrete pavement can be recycled as base and sub base material, thereby, reducing the requirement of virgin aggregate for the same. It would lead to innovation in design and construction of roads in a sustainable and environment friendly way at a lesser cost with better performance.

59 It is appreciated that provision of rain water harvesting is made compulsory in road projects specially on BOT (Build, operate and transfer). The use of appropriate geosynthetics in this process would yield better result. Appropriate design, selection of material and execution are essential to achieve the desired result.

60 Please let us hear from you Any question?

61 Prof. J. N. Mandal Department of civil engineering, IIT Bombay, Powai, Mumbai , India. Tel