What Are The Structure And Working Principle Of A Hydraulic Impact Pile Driver?
The hydraulic impact hammer is a new type of pile driver, driven by pneumatic pressure, and can adjust the hydraulic pressure according to the geological structure and soil quality to achieve a reasonable impact force. The medium and large-sized hydraulic impact hammer pile driver is commonly used for road guardrail piling and highway guardrail construction. Similar piling equipment includes: excavator impact hammer, road pile drivers, guardrail pile drivers, and road drilling equipment. Compared with diesel pile drivers, the efficiency of the hydraulic hammer pile driver can reach 70%~95%, while the efficiency of diesel hammer pile drivers is only 20%~30%. The hydraulic impact pile hammer has precise piling control capabilities and can perform piling operations in different geological structures; the hydraulic impact pile hammer has excellent characteristics in noise reduction, mechanical vibration, and noise, making it particularly suitable for the needs of urban construction. The hydraulic impact pile hammer has a significant emission reduction effect and is the mainstream trend in the future development of pile drivers.
According to its structure and principle, it can be divided into single-acting and double-acting types. Single-acting refers to the impact hammer core being rapidly released to a predetermined height by the hydraulic system, and the hydraulic impact pile hammer core drives the pile through free fall; double-acting refers to the impact hammer core being lifted to a predetermined height by the hydraulic system, and then receiving acceleration energy from the hydraulic system to increase the impact speed and drive the pile. This also corresponds to two piling theories. The single-acting hydraulic impact pile hammer corresponds to the heavy hammer and light impact theory, with advantages such as large hammer core weight, low impact speed, and long hammering time. The pile hammer has a large penetration depth per blow, is suitable for various shapes and materials of piles, has a low damage rate, and is especially suitable for concrete pipe piles. The double-acting hydraulic impact pile hammer corresponds to the light hammer and heavy impact theory, characterized by small hammer core weight, high impact speed, shorter hammer-pile action time, and large impact energy. Regardless of the type of pile driving hammer, the entire hammering process aims to maximize the efficiency of the hammer core before it strikes the pile head, ensuring sufficient momentum to impact the pile head and generate an instantaneous impact force far exceeding the hammer core's weight. This force overcomes the elastic energy absorption of the hammer-pile system, the lateral friction pressure on the pile body, and the end bearing resistance, driving the pile downwards and achieving a reasonable penetration depth (e value) through the soil.
Therefore, for steam hammers, diesel hammers, single-acting hydraulic hammers, and double-acting hydraulic hammers, given a fixed hammer core weight and stroke height, the maximum velocity standard deviation of the hammer core's downward movement can be estimated under ideal conditions. Simultaneously, the maximum actual downward velocity can be obtained through measurement. The ratio of these two values yields the velocity reduction rate for a specific hammer model, allowing for the calculation of the hammer's actual impact momentum. Based on the fundamental principles of impact in basic physics, using impact momentum as the basic performance parameter for equivalent circuit replacement between different hammer types is a sound approach.
Single-acting hydraulic impact pile driving hammers operate on the same principle as free-fall hammers commonly used in high-strain testing, making them suitable for high-strain testing methods. Double-acting hydraulic impact pile driving hammers, in addition to the impact energy converted from the hammer core's potential energy, also experience downward pressure from the hydraulic system on the hammer core. The impact force on the pile head is the resultant force of these two forces. This mode of operation is similar to the combined force generated by the downward movement of the hammer core and the explosion of atomized diesel fuel in the combustion chamber of a diesel hammer. Therefore, based on the working principle, both single-acting and double-acting hydraulic impact pile driving hammers are suitable for high-strain testing.
