The effect of changing the structural scheme of reinforcing strip foundations with short piles

In the work, mathematical modeling of the reinforcement of the strip foundation of shallow laying with short piles is performed in two variants: reinforcement at the level of the sole of the existing foundation, reinforcement from the soil surface. For comparison, short piles of different lengths are considered in both versions. In order to verify the possibility of determining the bearing capacity of the reinforced foundation as a conditional foundation of shallow laying, mathematical modeling of the conditional foundation was performed for both variants of the design solution. In mathematical modeling, not only the length varies, but also the pitch of the reinforcement piles, as well as soil conditions. The obtained results were analyzed with a comparison of all options. 
The results of the calculations showed that when using short piles, it is effective to switch to the reinforcement option, when there is no need to dig trenches to the level of the sole of the existing foundation, with the placement of the riser of the newly created foundation at the level of the paving or floor. This option excludes time-consuming work of manual digging of trenches, and also allows you to perform reinforcement work not with small grabs, but in an arbitrary manner. In general, this makes it possible to significantly reduce costs of labor, time and money. 
Research has established that increasing the pitch of the piles leads to a decrease in the bearing capacity of the reinforced foundation for both short and long piles, and the consideration of the foundations as conditional arrays is most consistent with the option with a pile pitch of 3d (600 mm). 
The results of the calculations also showed that the bearing capacity of the reinforced foundation, obtained by modeling in Plaxis, exceeds the bearing capacity calculated according to the recommendations of the standards. Therefore, the implementation of the load-bearing capacity of the piles and grillage of the newly created pile foundation during reinforcement improves the joint operation of its elements. 
 