Scope of Effective Application of the Vibration Method and Classification of Vibration Machines

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Analyzing the data given in § 1 and 2, the effect of the interaction of the vibrating body with the ground can be explained as follows. During vibrational immersion of elements into the ground, by introducing additional sign-alternating forces and/or torques, it is possible to significantly reduce the constant component of the force necessary for effective immersion, which makes it possible to immerse elements with the help of vibration machines of relatively small mass into the ground, the resistance to penetration of which in many times greater than the gravity of the vibrating system. In cases of significant changes in soil properties under the action of vibrations, it is possible to reduce not only the magnitude of the required constant force, but also the amount of energy expended on immersion.

During vibration driving or extraction, when the dynamic impact on the pile is carried out by a vibration exciter rigidly connected to it, the efficiency of the process is determined mainly by the application of significant periodic forces to the pile, which, together with constant forces (system gravity, inertialess pressing, extraction force) ensure the movement of the pile into ground.

In a number of cases (mainly when elements are immersed in low-moisture dense soils or when elements with a developed frontal surface are immersed,) it is advisable to use impact-vibration hammers in which the vibration exciter acts on the immersed element mainly by impacts. The shock-vibration mode can also have advantages over the vibration mode for inclined or horizontal immersion of elements.

To ensure effective immersion or extraction: the length of the element must be no more than 1/4 of the length of the elastic wave propagating in it. If this limit is exceeded, it is necessary to take into account the elastic deformations of the submerged element. Features of the process of immersion and extraction of long elements should be taken into account when selecting the parameters of vibration machines.

When immersing or extracting long elements, the mode of longitudinal elastic resonance can be effective, in which the frequency of the driving force is chosen close to the natural frequency of elastic vibrations of the immersed body.

The mass of an element immersed in a vibrational way is practically unlimited. The experience of vibration immersion of wells-shells weighing more than 200 tons is known.

During shock-vibration immersion, the mass of the immersed element, as a rule, should not exceed 3-5 tons, since for the most effective immersion by this method in conditions of significant frontal resistance, the ratio of the masses of the immersed element and the impact part of the impact-vibration hammer should approach unity; the use of vibratory hammers with a mass of the shock part exceeding 3-5 tons is limited by the durability of the mechanism, which sharply decreases with increasing mass.

The vibration method is most effective compared to other methods when immersing elements with a relatively small cross-sectional area. In this regard, the vibration method is most widely used when sinking metal sheet piles, casing pipes and shell piles, as well as during drilling operations.

The vibration method is most effectively used in water-saturated sandy and plastic clay soils, and the scope of the vibration method covers all types of sandy and clay soils up to a semi-solid consistency, inclusive, with a content of stony inclusions up to 40%. The successful experience of using the vibromethod in gravel soils is also known (with longitudinal-rotational vibrations of a shell equipped with teeth.)

The efficiency of using the vibration method depends on the shape of the immersed elements. So, for example, tubular elements that are not immersed from below have a number of features, the main of which are:

• the predominant influence of the lateral resistance of the soil;
• the formation of a soil plug in the cavity of the submersible element;
• vibrations of soil and water in the inner cavity of the shells.

The effectiveness of the vibromethod when immersing and extracting tubular elements is significantly increased when complex types of dynamic effects are applied to these elements. The classification of vibration machines according to the type of dynamic impact on the submersible element is shown in Fig. 1.