Experimental Investigation on Bamboo as Structural Pile

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Experimental Investigation on Bamboo as Structural Pile

Chapter · March 2021

DOI: 10.1007/978-981-15-9554-7_56

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as Structural Pile

Madhubala Mayilswamy, Anil Kumar Sharma, Surya Muthukumar, Jayakrishnan, Yamini Jayaprakash, Sakthipriya, and Amritha Velayudham

1 Introduction

Soil reinforcement techniques is used in the field of construction due to its versatile and flexible nature. Reinforced soil is used as a construction material by incorporating small percentage of material in the form of fibers, plates, solid rods, etc., to improve the tensile strength. The usage of natural inexpensive material as a reinforcement improves the sustainability in construction. This simple technique can cause a huge difference in the performance, cost, and sustainable nature of the project [1–3].

Bamboo is a perennial grass available in plenty in tropical, sub-tropical, and temperate zones [4]. It is a non-timber forest resource from large grass family [5].

There are around 1500 identified bamboo species in the world [6]. Bamboo is an easily available natural material used as a renewable resource in construction. It is a promising engineering composite material with fibers in one direction that gives high flexural strength to it [7–9]. Bamboo has wider application in the field of construction, as a building material for roofs, walls, also used for shoring and scaffolding [20]. It is used in stability of foundation pit excavation [10]. Studies show that it possesses high

M. Mayilswamy·S. Muthukumar (

B

⁾^·Jayakrishnan·Y. Jayaprakash·Sakthipriya· A. Velayudham

Department of Civil Engineering, Amrita School of Engineering, Amrita Vishwa Vidyapeetham, Coimbatore, India

e-mail:[email protected] M. Mayilswamy

e-mail:[email protected] A. K. Sharma

Department of Civil Engineering, National Institute of Technology Patna, Patna, India e-mail:[email protected]

Innovations, Lecture Notes in Civil Engineering 113, https://doi.org/10.1007/978-981-15-9554-7_56

631

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632 M. Mayilswamy et al.

compressive and tensile strength and also been used as a reinforcement in concrete [11].

Bamboo is also used as a foundation member in soft soil. Instability and large settlement of peats and soft soil under the construction of embankment is improved by bamboo piles which also increases the bearing capacity of soil [1]. Having high compression and tensile strength [3], bamboo’s strength can differ for different species based on the parts and moisture content.

Freshly cut bamboo possess high tensile strength, and it reduces gradually with its age. Selection of bamboo to be used in constructed is based on the seasoning and age. A well-seasoned bamboo should be around 3–6 years. The bottom portion of the seasoned bamboo possess high strength [12]. Slope reinforced with bamboo pile improves the stability by increasing the safety factor. The bearing capacity of a shallow footing placed on a sloped surface can be significantly increased by providing reinforcement through bamboo pile. The installation can improve the resistance to the lateral forces [13]. Bamboo piles can be widely used as a vertical reinforcement to improve the bearing capacity of sand in square footing.

Bamboo with branches is used as soil nails for hard soil and soft clay [14], which shows highest tensile capacity about 2.5–2.8 times than that of steel-pipe nails [15].

Bamboo pile performs better than geotextiles as a reinforcement in soil [16]. It is used as reinforcement in peat soil which has reduced settlement to a great extent [17]. Bamboo is used for stabilization and reinforcement to directly support the structure. From various studies, it is found that bamboo reinforcement can perform better than conventional steel piles, this is mainly due to the improved frictional resistance between the soil and the reinforcement and the inherent fibrous nature of the grass. The length and diameter should be decided based on the requirement [7].

The main problem with a natural reinforcement material is its durability. Bamboo is durable for 2 years without any treatment, and with preservatives, the durability can be improved to 4–7 years. But from the various techniques adopted over years, it is found that soaking bamboo in flowing water can improve the durability more than 10 years. Cutting and slicing of the natural bamboo trunk can reduce the strength, so it will be used in the original condition to retain the properties [7].

In the present study, it is aimed to understand load-settlement behavior of bamboo piles, to find the ultimate load-carrying capacity of bamboo piles and to compare the results of various dimensions bamboo piles.

2 Materials 2.1 Sand

River sand collected from Kaveri river basin near Kulithalai, Tamilnadu, is used for the test. The physical properties of sand are tested as per IS specifications and

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Table 1 Properties of soil

Properties Value

Coarse sand 2.9%

Medium sand 34%

Fine sand 61.3%

Silt and clay 1.8%

D10 0.20 mm

D30 0.32 mm

D60 0.56 mm

Coefficient of uniformity, Cu 2.8 Coefficient of curvature, Cc 0.91

IS classification SP

according to UCS the soil is classified as poorly graded sand (SP). The properties of sand are listed in Table1.

2.2 Bamboo

Bamboo has a unique structure which is fiber reinforced in unidirectional with multiple nodes along its length [2,18]. It is mostly used construction material because of its good mechanical properties compared with other materials. The density of bamboo is about 700–800 kg/m³, and the fiber weight is around 60–70% of the total weight. It possess high tensile strength along the fiber direction [7]. Both treated and untreated bamboos possess good physical and mechanical properties [19]. The properties vary with respect to age and various parts of bamboo. Naturally available bamboo was collected from, bamboo market, Gandhi park in Coimbatore, Tamilnadu, for the model test.

Laboratory model tests were carried out to study the load-settlement behavior of individual bamboo piles which is hollow inside with a knot at the base of pile under vertical loading condition on medium dense sand. Tests were performed by varying the dimensions of bamboo piles, three different inner and outer diameters and three different lengths are shown in Fig.1. The dimensions of the bamboo pile are selected based on the natural availability and to satisfy the model test condition.

Bamboo pile dimensions along with specifications are given in Table2.

2.3 Pile Cap

Mild steel plate of circular in cross section with 150 mm diameter and 8 mm thickness is used as a pile cap kept at the top of all bamboo pile tested.

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Fig. 1 Bamboo piles

Table 2 Bamboo pile

dimensions Bamboo piles Inner diameter

(ID) (mm)

Outer diameter (OD) (mm)

Length (mm)

C1-P1 60 70 300

C1-P2 50 65 300

C1-P3 24 34 300

C2-P1 60 70 200

C2-P2 50 65 200

C2-P3 24 34 200

C3-P1 60 70 100

C3-P2 50 65 100

C3-P3 24 34 100

3 Experimental Test Setup

The load-carrying capacity of bamboo pile was analyzed using a series of tests conducted on bamboos with varying inner and outer diameters and lengths. The vertical load tests were carried in a model tank setup of size 550 mm ×550 mm

×550 mm using a loading frame of capacity 50 kN. The dimensions of the tank were chosen, so that there will not be interference between the walls of the tank and the failure zone around the piles. It is also maintained to satisfy the condition to test end bearing pile. The tests were conducted for a single pile with a cap to analyze the improvement in bearing capacity. The foundation medium was prepared using river sand. The sand was filled in the tank setup by sand raining technique.

The height of fall required for achieving a relative density of 50% was found by pouring sand from varying heights. This height of fall was found to be 280 mm to achieve 50% relative density [20], and to maintain uniformity in the series of tests performed, it was ensured that throughout the filling process this height was

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Fig. 2 Vertical loading setup

constantly maintained. After filling up to the top of the pile, the bamboo was inserted to the soil to simulate the actual field placement condition. Pile was kept at the center of the tank. Experimental test setup for vertical loading is shown in Fig.2.

4 Test Procedure

The pile cap was kept at the top and vertical compressive load was applied to bamboo pile through a hydraulic jack, which was supported centrally at the bottom flange of the steel girder made of channel sections. The vertical load tests were conducted on piles as per procedure recommended by IS 2911 (Part 4)-[21]. The proving ring and two LVDTs were placed in position over the pile cap. Axial load was applied in increments, and it was observed through 50 kN proving ring placed over the pile cap. Each increment of loading was maintained until the pile settlement become less than 0.02 mm/min. The vertical deflection of the pile was measured by LVDT corresponding to the load, and when the deflection of the pile ceases, the next load increment is applied. The test was proceeded until the pile achieves its ultimate axial capacity for the corresponding failure load. The load-settlement curve was plotted for vertical loading case, and safe load is calculated by minimum of two conditions for individual pile. Bamboo piles of the various inner and outer diameter and length were used as given in Table2.

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Table 3 Safe load of bamboo piles for vertical loading Bamboo piles Inner diameter (ID)

(mm)

Outer diameter (OD) (mm)

Length (mm) Safe load (kN)

C1-P1 60 70 300 0.511

C1-P2 50 65 300 0.367

C1-P3 24 34 300 0.188

C2-P1 60 70 200 0.325

C2-P2 50 65 200 0.164

C2-P3 24 34 200 0.064

C3-P1 60 70 100 0.195

C3-P2 50 65 100 0.13

C3-P3 24 34 100 0.044

5 Results and Discussions 5.1 Bamboo Piles

From the vertical pile load tests, the load-carrying capacity of bamboo piles for various conditions were obtained [22]. The safe load-carrying capacity of bamboo piles for different inner and outer diameters and lengths are reported in Table3.

Bamboo pile of 300 mm length and ID60 mm-OD70 mm had larger load- carrying capacity than ID50 mm-OD65 mm, ID24 mm-OD34 mm diameters of length 300 mm. For length 200 mm, 100 mm with respect to same diameters, ID60 mm and OD70 mm had larger load-carrying capacity. Table3 clearly shows that larger diameter bamboo pile shows higher load-carrying capacity and increase in length bamboo pile shows an increase in load-carrying capacity.

Load-settlement curves for bamboo piles shows ID60 mm-OD70 mm diameter piles that have higher peak than ID50 mm-OD65 mm, ID24 mm-OD34 mm diameters for the pile length of 300 mm, 200 mm, 100 mm, which concludes that load-carrying capacity is high for larger diameter bamboo piles.

Figure3shows that, for 300 mm length bamboo pile with diameter ID60 mm- OD70 mm, ID50 mm-OD65 mm, ID24 mm-OD34 mm, maximum diameter pile C1-P1 performs better with a greater load-carrying capacity, whose safe load is 28%

greater than C1-P2 and 63% greater than C1-P3.

Figure4shows that, for 200 mm length bamboo pile with diameter ID60 mm- OD70 mm, ID50 mm-OD65 mm, ID24 mm-OD34 mm, maximum diameter pile C2-P1 performs better having greater load-carrying capacity, whose safe load is 50% greater than C2-P2 and 80% greater than C2-P3, here bamboo pile C2-P1 curve was high.

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Fig. 3 Load versus settlement for vertical loading of bamboo pile with 300 mm length

Figure5 shows that for 100 mm length bamboo pile with diameter ID60 mm- OD70 mm, ID50 mm-OD65 mm, ID24 mm-OD34 mm, maximum diameter pile C3-P1 performs better has greater load-carrying capacity, whose safe load is 33%

greater than C3-P2 and 77% greater than C3-P3. Here bamboo pile C3-P1 curve shows high load-carrying capacity.

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Bamboo piles of ID60 mm-OD70 mm, ID50 mm-OD65 mm, ID24 mm-OD34 mm diameters with respect to 200 mm length piles (C2-P1, C2-P2, C2-P3) show maximum percentage increase in safe loads than 300 mm length and 100 mm length piles, change in length of bamboo piles influence the load-carrying capacity of piles, in 200 mm length piles D/B ratio was maintained as 2–3.5.

The durability of the untreated bamboo pile is around 2 years without any strength reduction. To improve the performance and durability, treatments like bitumen coating, oil coating, borax with water preservative can be performed.

6 Conclusion

From the experimental investigation on bamboo piles, the following conclusions can be made

• It is observed that the installation of bamboo piles as a vertical reinforcement in loose sand has considerably increased the bearing capacity of the footing.

• The series of tests showed that the soil confinement due to the vertical reinforcement has improved the bearing capacity and controlled the settlement to a greater extent.

• The pile condition C1-P1 has shown an improvement of around 63% compared to the C1-P3, and C2-P1 has shown an improvement of around 80% compared to the C2-P3, and C3-P1 has shown an improvement of 77% compared with C3-P3.

• The overall tests can be concluded that the bearing capacity increases with increase in diameter and length of the pile.

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• Bamboo pile length influences the load-carrying capacity of piles, and percentage increase in safe load is maximum when D/B ratio is maintained between 2 and 3.5.

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