A Comparative Study of Concrete Expanded Plates Pile and Common Pile Uplift. Bearing Capacity

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1 WEI TIAN et al: A COMPARATIVE STUD OF CONCRETE EXPANDED PLATES PILE AND COMMON PILE A Comparative Study of Concrete Expanded Plates Pile and Common Pile Uplift Bearing Capacity Wei Tian, ongmei Qian, 2*, Ruozhu Wang. Civil Engineering Institute, Jilin Jianzhu University, Changchun, Jilin, 308, P.R.China 2. The Structure and Earthquake Science and Technology Innovation Center of Jilin Province, Changchun, Jilin, 308, P.R.China Abstract By applying the finite element method with the help of the ANSS program, the effect of the soil around the concrete expandedplates pile and the common pile under vertical forces is analyzed. According to the distribution of the pile soil stress, the concrete expandedplates pile under vertical forces, the impact of bearing expandedplates on bearing capacity can be calculated, which can provide a reliable theoretical analysis for further improving the pile bearing capacity calculation formula. Keywordsconcrete expandedplates pile; pile soil effect; uplift bearing capacity; simulation analysis I. INTRODUCTION Concrete expandedplates pile is a new and reliable technology. Because of its structure and forming mechanism, it can improve the compressing and uplifting capacity through more bearing expandedplates. The advantages of it are such as higher compression bearing capacity of one single pile, less consumption materials, simpler construction operation, shorter construction period and wider application area []. However, there is very little studies about the further research on the comparison between uplifting capacity of the concrete expandedplates pile and the common pile. This paper is to study the stress and strain state of the concrete expandedplates pile and the common pile in the same load through the computer simulation and comparison analysis. II. MODEL FORMULATION AND BASIC PARAMETERS OF THE CONCRETE EXPANDEDPLATES PILE AND THE COMMON PILE A. Assumptions In order to make the model closer to the actual situation, according to the characteristics of the pile body and the surrounding soil, the following assumptions are made in the establishment of the analysis model[2]: ) The soil layer is a homogeneous silty clay; 2) It is assumed that the common work of the pile and soil is the axial symmetry; 3) The reinforced concrete pile is linear elastic body; 4) The soil mass is a homogeneous continuous elastic plastic body, while the influence of geometrical nonlinearity is considered; 5) It is assumed that the top of the pile lie in the same plane as the top of the soil, and the center of the pile is the same as the center of the soil. B. Modeling, Design Parameters and Loading Conditions ) Calculation model diagram The affected zone of the soil around the pile is about 0 times of the pile diameter, and the soil is considered to have little effect on the soil while the distance is beyond the 0 times. Therefore, the boundary of the soil can be treated by threeconstraint. It is assumed that the pile length is 5000mm, the diameter is 500mm, the pile diameter is 500mm, the slope angle is 30 degrees, the position from the top of the pile is 3000mm, the area of the soil radius is 7000mm, and the range of 8000mm is DOI 0.503/IJSSST.a ISSN: x online, print

2 WEI TIAN et al: A COMPARATIVE STUD OF CONCRETE EXPANDED PLATES PILE AND COMMON PILE from the top to the bottom of the pile. /4 of structure was analyzed and the model of pile and soil was used to build the models separately [3]. Common concrete pile model is SZ, and the concrete expandedplates pile model is PZ. The calculation model diagram is shown in Fig (). 2) Parameter setting All the parameters of the pile and soil are in the table. The pile and soil friction coefficient is ) Loading process Since the assumption of the both piles is in the case of the axial symmetry, the threedimensional problem is converted to the axisymmetric problem. /4 symmetric structure is selected, setting the common direction constraint on the two section. The Xcomponent, component and Zcomponent of the lateral and lower surface of the soil are restrained, and the soil model is applied to the gravity stress. The gravity stress in ANSS is achieved by setting the density of the material and the acceleration of gravity. VOLUMES VOLUMES TPE NUM AUG :4:49 TPE NUM AUG :49:28 Z X 500,700 Z X SZ PZ Figure. The Model of Pile of Two Kinds of Form TABLE Ⅰ. CALCULATION OF PILE AND SOIL Parameter Model Elastic modulus (KPa) Poisson ratio (υ) Gravity stress (kn/m3) Cohesive force (C,KPa) Friction angel (φ) Expansion angel (β) Soil 2.5e Concrete 2.5e Analysis of computing result of the concrete expandedplates pile and the common pile Through the simulation analysis, it is concluded that the common uniformsection pile (SZ) and the concrete expandedplates pile (PZ) displacement, vertical tensile force under the action of stress and strain nephogram. Comparison of both piles nephogram changes, the corresponding conclusion is made. The change rule of the both piles displacement, stress and strain can be found by the change of the pile and the surrounding soil. Both kinds of piles displacement nephogram are shown in Fig.(2). It can be seen from the figure that the displacement of the soil around PZ is larger than that of SZ due to the existence of the bearing expandedplates. In contrast, the maximum displacement of PZ is far less than that of SZ under the same load. It shows that the load bearing capacity of SZ is smaller than that of PZ. DOI 0.503/IJSSST.a ISSN: x online, print

3 WEI TIAN et al: A COMPARATIVE STUD OF CONCRETE EXPANDED PLATES PILE AND COMMON PILE SUB =0 U (AVG) RSS=0 D =4.72 S =4.72 AUG :39:57 SUB =0 S (AVG) RSS=0 D =3.072 AUG :47:35 S =68.05 S = SZ component displacement fringe , SUB =0 AUG :47:25 PZ component stress fringe Figure 3. Component of Stress Fringe U (AVG) RSS=0 D =3.072 S =3.072 SUB =0 SZ (AVG) RSS=0 D =4.72 S =2.94 S =5.226 AUG :40: , PZ component displacement fringe Figure 2. Component Displacement The normal stress, shear stress and the first principal stress nephogram of both kinds of piles are shown in Fig.(3), Fig.(4) and Fig.(5) SZ Zcomponent shear stress fringe SUB =0 AUG :40:06 S (AVG) RSS=0 D =4.72 S =32.72 S = AUG SUB =0 3:47:45 SZ (AVG) RSS=0 D =3.072 S = S = ,700 PZ Zcomponent shear stress fringe Figure 4. Zcomponent Shear Stress Fringe SZ component stress fringe It can be observed that the whole pile force is roughly the same, stress from the top to end of the pile normal DOI 0.503/IJSSST.a ISSN: x online, print

4 WEI TIAN et al: A COMPARATIVE STUD OF CONCRETE EXPANDED PLATES PILE AND COMMON PILE decreases gradually. component stress of PZ is greater than that of SZ, and component stress of pile top range increases in figure 3. In Figure 4, Zcomponent soil shear stress of PZ is more than that of SZ, and Zcomponent shear stress is greater. In Figure 5, soil first principal stress of PZ is more than that of SZ, and the maximum of first principal stress is on the top of the pile, the minimum of first principal stress is in the bottom of the pile. Under the same load, fist principal stress of PZ is more than that of SZ. The results show that up to the damage, bearing capacity of PZcan bear much more load up to the damage than SZ,and PZ can make full use of its body. It can be observed that, ZComponent shear total strain of PZ is less than SZ, and the maximum of total strain is at the bottom of both piles in figure 6. In Figure 7, elastic strain of PZ is less than that of SZ. The maximum of elastic strain is at the top of both piles soil and the minimum of elastic strain is at the bottom of both piles soil. In figure 8, soil plastic strain of PZ is less than that of SZ, and the maximum of plastic strain is at the bottom of the both piles. The results show that PZ has small strain than SZ under the same load. The existent of bearing expandedplates has changed the soil damage state, so it can improve the bearing capacity of PZ much more. SUB =0 S (AVG) D =4.72 S =4.2 S =786 AUG :40:43 SUB =0 EPTOZ (AVG) RSS=0 D =4.72 S = S = AUG :4: SZ first principal stress fringe SZ ZComponent shear total strain fringe SUB =0 S (AVG) D =3.072 S = S =90 AUG :47:53 SUB =0 EPTOZ (AVG) RSS=0 D =3.072 S = S = AUG :48: , ,700 PZ first principal stress fringe PZ ZComponent shear total strain fringe Figure 5 First Frincipal Stress Fringe Figure 6 ZComponent Shear Total Strain Fringe The total strain, elastic strain and plastic strain fringe of both kinds of piles are shown in Fig.(6), Fig.(7)and Fig.(8). DOI 0.503/IJSSST.a ISSN: x online, print

5 WEI TIAN et al: A COMPARATIVE STUD OF CONCRETE EXPANDED PLATES PILE AND COMMON PILE SUB =0 EPEL (AVG) RSS=0 D =4.72 S =.545E03 S =.876E03 AUG :4:3 SUB =0 EPPL (AVG) RSS=0 D =4.72 S =.28E03 AUG :4:23 S = E03.387E03.229E03.72E04.866E04.244E03.402E03.560E03.78E03.876E03 SZ Component of elastic strain fringe.28e SUB =0 AUG :48:38 SZ Component of plastic strain fringe EPEL (AVG) RSS=0 D =3.072 S = S =.826E03 SUB =0 EPPL (AVG) RSS=0 AUG :48:49 D =3.072 S =.249E03 S = E03.574E03.294E03.43E04.266E03.546E03.826E03 500,700 PZ Component of elastic strain fringe Figure 7 Component of Elastic Strain Fringe III. CONCLUSION.249E ,700 PZ Component of plastic strain fringe Figure 8 Component of Plastic Strain Fringe Through the above analysis, it can be concluded that the damage state of concrete expandedplates pile is obviously different from that of concrete common pile under the vertical tension. Due to the existence of the bearing expandedplates, the damage state of the top and down around the soil has been changed. Compared to the common pile, concrete expandedplates pile has a different friction calculation range in the side of the pile, much more uplifting capacity and obviously less displacement under the same load. Meanwhile, soil damage state has been changed on the top of plate which has the punching or slip damage. It needs to be further studied in order to provide reliable basis for the calculation of the concrete expandedplates pile uplifting capacity. ACKNOWLEDGMENTS This work is financially supported by National Natural Science Foundation of China ( ). REFERENCES [] Kai Wei,Wancheng uan,"analysis of deep water pile foundation based on threedimensional potentialbased fluid elements". Journal of Construction Engineering, Vol.48, no.9, pp.0, 203. [2] ongmei Qian, Xinsheng in, Rongqing Jiang. defining the Calculate Model about the Soil Stress under the UnderReamed of the PushExtend MultiUnderReamed Pile by Using the Theory of Sliding Line. Journal of Jilin University (Earth Science Edition), Vol.34, no.0, pp. 8789, 202 [3] Q ongmei, Z Dapeng, X Xuewen. the research on the ultimate bearing capacity of soil around the pushextend multiunderreamed pile at sliding failure state". Advances in Civil Structures IV, Trans Tech Publications, 204. DOI 0.503/IJSSST.a ISSN: x online, print