CALCULATION OF THE MAXIMUM ALLOWABLE LOAD ON A REINFORCED CONCRETE PILE IN THE PROCESS OF DRIVING IT INTO THE SOIL

Abstract

Due to the lack of technical standards (DSTU) in Ukraine for the technology and quality control of the installation of driven piles, the conditions for high-quality performance of pile driving are often violated, for example, the driving force exceeds the strength of the pile material. This leads to the destruction of piles, which is most characteristic of sandy soils. In the project documentation for the installation of driven piles, with rare exceptions, there are no restrictions on the value of the driving force based on the strength of the pile based on the material, mainly due to the difficulties that arise when calculating the maximum permissible load on the pile when it is deepened by driving the pile.
According to amendment No. 1 to DBN V.2.1-10-2009 [2] the amount of Rstv. is determined by calculating the strength of the material in accordance with the requirements of DBN B.2.6-98; 2009 [3], while considering the pile as a rod rigidly clamped in the soil in a section located at a distance ℓ1 from the point of application of the compressive force (see Fig. 1 and dependencies (2), (3)).
According to DBN B.2.6-98; 2009 [ 3 ], the amount of compressive load allowed for the pile material is determined by calculating the pile as an eccentrically compressed reinforced concrete element under the action of a longitudinal force, while taking into account the random eccentricity eo, which in any case must take at least 1/600 of the distance between its cross-sections, fixed from displacement and 1/3 - from the height of the cross-section. In addition, it is also necessary to take into account the influence of longitudinal deflection by multiplying the value of the random eccentricity eо by the coefficient η according to dependence (5).
The specified recommendations of the DBN on determining the value of the compressive load allowed for the pile material refer to the pile as an eccentrically compressed reinforced concrete element in a static state, which does not take into account the influence of technological factors in the process of pile compression.
Our experience of sinking piles at dozens of sites has shown that the impact of the pressing technology on the permissible load on a reinforced concrete pile during its sinking is manifested in the form of an increase in eccentricity due to technological factors. In table 2, the reasons affecting the eccentricity of the load on the pile in the process of its immersion are considered in various ways of creating a compressive force: due to the weight of the structures of buildings and structures; due to the weight of equipment or anchor loads; due to anchor devices.
The article draws the following conclusions.
1. When calculating the maximum permissible load on a reinforced concrete pile in the process of pressing it into the ground, it is necessary to take into account, in addition to the recommended DBN B.2.6-98:2009 [ 3 ] random eccentricity and eccentricity from longitudinal deflection, as well as technological eccentricity by multiplying the value of random eccentricity by the coefficient of working conditions piles when pressed.
2. We proposed the values of the coefficients of pile operating conditions for determining the calculated technological eccentricity for different ways of creating a compressive force and different ways of transferring the compressive load to the pile (through the head or through the side faces) (see Table 3). These values are empirical, they will be adjusted as experience is gained in the application of the pile driving method.