Numerical Analysis Of Soil Arching Effect Between Super Long Piles Under Horizontal Load

In recent years, with the increasement of high-rise buildings, long-span bridges and large-scale hydraulogy projects, super- long piles are widely used because of its high bearing capacity and uniform settlement. Since the horizontal load has a great impact on these structures, research of horizontal bearing capacity in super- long piles is very meaningful. For a long time, people tend to focus on the research of the influence soil arching effect has on the anti-slip of soil. However, little research has been done on the soil arching effect behind piles subjected to the horizontal load and the influence it has on the horizontal bearing capacity. In this paper, the soil arching effect of super- long piles in rows when subjected to the horizontal load is studied and the detailed aspects are addressed as below:1. A finite element model considering the interaction between pile and soil is established. The Mohr-Coulomb model is selected as the constitutive model of soil. Furthermore, the actual condition is simulated by considering the geostress equilibrium, setting the interface and boundary conditions. The result is verified by the comparison with experimental results in relevant papers.2. By establishing a finite element model of 3×1 single-row super long piles, the variation trends of soil arching effect behind and along the piles are both analyzed. The results show that the soil arching effect displays obviously on the top of piles and at the region within two to three times the space between two piles. Meanwhile, the variation law of horizontal frictional resistance along piles is discussed. It shows the more obvious soil arching effect is, the larger horizontal frictional resistance is.3. For the single-row piles, by changing the space between two piles, internal friction angle, cohesion, stiffness ratio of pile and soil and length-diameter ratio of piles, the influence of these parameters on the soil arching effect and the variation law of horizontal frictional resistance are studied. The results show that the horizontal stress arch between piles disappears with the increasement of the space between two piles and the ultimate pile space is six times the diameter of the pile. The internal friction angle and the cohesion are positively relevant to the soil arching effect and the horizontal frictional resistance, while the stiffness ratio of the pile to the soil shows a negative relation to the soil arching effect. As the length-diameter ratio of piles increases, the soil arching effect decreases. The soil arching effect remains unchanged at L/D=75.4. By adopting a model of 3×2 double-row super long piles, the difference in soil arching effect between the front and rear piles, and the influence this difference has on horizontal frictional resistance and shaft deflection between them are discussed. It shows that no soil arch exists between two of front piles, and the soil arch mainly appears at the region within two times the space between two rows in rear piles.5. By changing the space between two rows, horizontal load, length of piles and piles arrangement, the degree of soil arching effect, the variation law of horizontal frictional resistance and shaft deflection are analyzed. The results show that the space between two rows shows inverse relation with the soil arching effect and the maximal row space is eight times the diameter of the pile. On the contrary, the horizontal load and length of piles presents a positive relation with the soil arching effect and the maximum length of piles affecting the soil arching e ffect between two rear piles is 50 m. The soil arching effect is more obvious in parallel piles than quincuncial piles. The horizontal frictional resistance is larger in parallel piles and the shaft deflection is relatively smaller.6. Two kinds of soil arch formed between respectively single-row piles and double-row piles are compared under the condition of other factors being equal. It is found that the soil arching effect and horizontal frictional resistance in single-row piles are similar to those in rear piles. However, shaft deflection in double-row piles is much smaller than that one in single-row piles. Therefore, the capacity of resisting shaft deflection in double-row piles is much stronger than that one in single-row piles.