Proceedings of 29th Research World International Conference, Las Vegas, USA, 16th-17th March 2017, ISBN: 978-93-86291-88-2

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INFLUENCE OF PILE INCLINATION ON BATTER PILE GROUPS SUBJECTED TO LATERAL LOADING IN SAND

1TANVI SINGH, 2V.K.ARORA

1,2Dept. of civil engineering, NIT Kurukshetra, Haryana 136119 E-mail: 1tanvisinghnitkkr@gmail.com, 2aroravk1@gmail.com

Abstract- When a structure is subjected to large amount of lateral load, batter piles are used in combination to vertical piles. Batter piles convert overturning moment into compression and tension forces. Little literature is available about the behavior of batter piles in group. In present study 66 tests were conducted on batter pile groups under lateral load with batter pile inclined at 20º, 25º, 30ºand 35º. Results indicate that negative batter pile individually as well as in a pile group show less amount of deflection and group efficiency is greater than sum of individual piles efficiency. Further as batter angle increases from 20 º to 25 º pile capacity increases and decreases beyond 25 º Key words- Batter piles, Batter pile groups, Lateral loading, Batter angle, sand I. INTRODUCTION Pile foundations are used to carry and transfer structural load to bearing strata at greater depth below ground surface. Foundations of offshore structure and high rise building are subjected to lateral load of high magnitude due to water wave ,wind load and ice forces, to resist these lateral forces batter piles are used. Batter piles are more capable of resisting lateral forces because of its ability to resist large lateral forces along its length and to convert overturning movement into compression and tension forces. In past various theoretical studies and laboratory tests have been carried out to study the behavior of batter piles and concluded that negative batter pile offer more resistance to lateral load. Murthy [1] and Prakash and Subramanyam [2] conducted laboratory tests in sand using model batter piles and confirmed that negative batter piles offer more resistance to lateral loading. Matlock [3], Brown [4],Rollins[5] and McVay [6] conduced full scale lateral load test on vertical pile group and indicated that deflection of per pile in a group shows more deflection than single pile when subjected to same amount of lateral load. So, use of batter pile was likely toenhance the resistance to lateral load capacity of soil. Various studies have been done to study the effect of batter angle, using model testing Meyerhof of [7], Hanna and Nguyen [8] concluded that increasing the inclination angle will increase pullout capacity where as Awad and Ayoub[9] concluded from there experimental analysis that pullout capacity decreases with increasing inclination angle. On the other hand Hanna and Afram [10] showed no significant change in pullout capacity due to change in inclination. Theoretical analysis carried out by Chatopadhyay and Pise [11] concluded, for same length of piles uplift capacity increases with increase in inclination up to inclination angle 20degree and then decreases. Due to various contradictory result present in literature an attempt

have been done to study the effect of pile inclination on load bearing capacity of batter pile group under cyclic lateral load test. Present study have been carried out on different pile groups rather than single pile because of fact that group behavior of pile was different than single pile and piles generally used in groups in field and little literature is available on behavior of batter pile group. 2.1 Model testing tank: Experimental program have been carried out on rectangle steel tank of size 1m ×2m and depth 1m, wall thickness was 5mm with front wall made of glass. The testing tank was kept large enough to avoid the boundary effect It was provided with pulley arrangement for providing lateral load and was fixed to ground in soil mechanics lab of NIT Kurukshetra to avoid any external disturbance .The tank was filled using rainfall method of sand filling. In present test the density achieved was 1.66g/cc .Figure 1 shows the experimental setup.

2.2 Soil used: The soil used in the model test was sand taken from the banks of river Yamuna from a village near Radaur in Yamunanagar district of Haryana. It is poorly

Influence of Pile Inclination on Batter Pile Groups Subjected to Lateral Loading In Sand

Proceedings of 29th Research World International Conference, Las Vegas, USA, 16th-17th March 2017, ISBN: 978-93-86291-88-2

14

graded sand and properties of sand are tabulated in table I 2.3 Model piles: Piles used were aluminum pipes with outer diameter 20mm and wall thickness of 1mm.Total length of pile was kept 0.90m with embedded length of 0.80m

load could uniformly distributed among all pile uniformly. Mild steel plate of thickness 2mm was used for pile caps. Vertical and inclined holes (at 20º, 25º, 30ºand 35º) with 20mm diameter were drilled. The 20mm extra dimension was provided for attaching hooks to both sides of plates so that wire can be fixed to hooks to both sides and load can be applied through wires. Total 34 number of pile caps were fabricated, 8set of pile cap on each batter angle and 2 pile cap having vertical hole. III. TEST PROGRAM Tank was filled using rainfall method of sand filling up to a height of 90cm from bottom of tank. Pile caps were placed at the center of tank to guide vertical and batter pile. Load hanger was attached to the hooks attached with in pile caps to apply lateral load. Dial gauge was kept in contact with pile cap to measure the deflection. Load increment of 2kg was maintained each time till the dial gauge showed no deflection. Load increment was done till deflection reaches its limiting value similarly unloading and reloading of load had been done to test these pile for cyclic loading. Total numbers of 66 tests were performed on piles in sand 16 set on each on batter angle (20º, 25º, 30ºand 35º) and 2 on vertical pile group, to study the effect of pile inclination on load carrying capacity of batter pile group. In present study variable were batter angle and number of piles and rest of other experimental condition were kept constant. Each reading was carefully observed and recorded load deflection

curve have been plotted to study the deflection behavior of each pile group. Table II shows summary of test performed.

Table II summary of test performed

IV. RESULTS AND DISCUSSION From the plot of loadvs settlement for each test various comparisons have been made. Note: - B= batterpile, V=vertical pile 4.1 Effect of direction of pile inclination To study the effect of direction of pile inclination comparison of deflection behavior of single vertical, positive and negative batter piles have been done. A graph between load verses deflection has been plotted and it was found that initially under the same amount of lateral load the deflection was almost same but as load increases, deflection of negative batter pile less than vertical batter pile and deflection of positive batter pile was more than vertical pile as shown in Figure 3 and also when pile group contains negative batter pile it showed less deflection in comparison to pile group which containing positive batter piles. Result obtained was in accordance Murthy [1] and Prakash and Subramanyam [2], they performed lateral tests on model batter piles in sandy soil and reported that negative batter pile offer more resistance to deformation than positive batter pile.

Figure2 comparison of single vertical, positive and negative

batter pile

Influence of Pile Inclination on Batter Pile Groups Subjected to Lateral Loading In Sand

Proceedings of 29th Research World International Conference, Las Vegas, USA, 16th-17th March 2017, ISBN: 978-93-86291-88-2

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4.2 Effect of batter angle A.Nazir [13] studied the influence of pile inclination using single batter pile inclined at 0º, 10º, 20ºand 30º at variable pile length in loose, medium and dense sand and found in medium and dense sand pullout capacity increases with increase of batter angle attains maximum value at approximately20º and then decreases. To study the effect of pile inclination (batter angle) on load bearing capacity of batter pile group we plot maximum load resisted by each pile cap at each batter angle (Figure 3). The plot shows that when batter angle increases from 20-25 load resisting capacity increases and when batter angle increases from 20º to 35º load resisting capacities decreases. The Peak value was obtained in graph was at 25ºand hence was most efficient batter angle in resisting lateral load .From the graph it was also observed that load resisting capacity varies prominently in pile group containing negative batter piles. Result obtained were close to the finding of A.Nazir

Fig 3 comparison curves for maximum load resisted by each

pile cap at batter angle 20, 25,30and 35 degree CONCLUSIONS Negative batter piles offer more resistance to deformation as compared to positive batter piles Also pile group containing negative batter piles offer more resistance to deformation as compared to pile group containing positive batter piles. Effect of batter angle

is parabolic, that is as batter angle increases from 20º to 25º pile capacity increases and beyond 25 º batters angle the load carrying capacity decreases. Effect of change in batter angle was prominent in negative batter pile and also groups containing negative batter piles REFERENCES [1] Murthy, V. N. S. (1964). Behaviour of battered piles

embedded in sand and subjected to lateral loads. In Proc. Of Symp. on Bearing Capacity of piles, Roorkee, India (pp. 142-153) 2. Prakash, S., & Subramanyam, G. (1965). Behaviour of battered piles under lateral loads. Indian J. of Soil Mech. and Found. Eng, 4(2), 177-196.

[2] Matlock, H., Ingram, W. B., Kelley, A. E., &Bogard, D. (1980, January). Field tests of the lateral-load behavior of pile groups in soft clay. In Offshore Technology Conference. Offshore Technology Conference.

[3] Brown, D. A., Reese, L. C., & O'Neill, M. W. (1987). Cyclic lateral loading of a large-scale pile group. Journal of Geotechnical Engineering, 113(11), 1326- 1343.

[4] Rollins, K. M., Lane, J. D., & Gerber, T. M. (2005). Measured and computed lateral response of a pile group in sand. Journal of Geotechnical and Geoenvironmental Engineering, 131(1), 103-114.

[5] McVay, M. C., Wasman, S. J., Consolazio, G. R., Bullock, P. J., Cowan, D. G., &Bollmann, H. T. (2009). Dynamic soil–structure interaction of bridge substructure subject to vessel impact. Journal of Bridge Engineering, 14(1), 7-16.

[6] Meyerhof, G. G. (1975, July). Uplift resistance of inclined anchors and piles: Conference. Session three. 9F, 22R. PROC. EIGHTH INT. CONF. ON SOIL MECH. FOUND. ENGNG, MOSCOW, 1973, V2. 1, 1973, P167–172. InInternational Journal of Rock Mechanics and Mining Sciences &Geomechanics Abstracts (Vol. 12, No. 7, p. 97). Pergamon.

[7] Hanna, A. M., & Nguyen, T. Q. (1986). Ultimate skin friction of single batter piles in sand. In Proceeding of the international conference on deep foundations. Beijing (pp. 100-8).

[8] Awad, A., &Ayoub, A. (1976). Ultimate uplift capacity of vertical and inclined piles in cohesionless soil. In Proceedings of the 5th international conference on soil mechanics and foundation engineering, Budapest (Vol. 1, pp. 221-227).

[9] Afram, A. (1984). Uplift capacity of battered piles in sand (Doctoral dissertation, Concordia University).

[10] Chattopadhyay, B. C., &Pise, P. J. (1986). Uplift capacity of piles in sand.Journal of Geotechnical Engineering, 112(9), 888- 904.

[11] Prakash, S., & Subramanyam, G. (1965). Behaviour of battered piles under lateral loads. Indian J. of Soil Mech. and Found. Eng, 4(2), 177-196.

[12] Nazir, A., & Nasr, A. (2013). Pullout capacity of batter pile in sand. Journal of advanced research, 4(2), 147-154.