Principle of hydraulic system of static pressure pile driver

What is the working principle of static pile driver?

(1) Because the system pressure oil flows from the hydraulic pump to the concentrator through two 90-degree bent steel pipes, when the working pressure reaches 10- 16MPa, the natural frequency of the steel pipe at the elbow is excited by the hydraulic pressure of the liquid flow, causing the pipeline to vibrate violently, thus radiating strong noise. After research, it was decided to cut off the elbow of one of the 90-degree steel pipes and replace it with a hydraulic hose with a diameter of 32mm and a length of 700mm and four layers of steel wire wound around it. In this way, in the working pressure range, the liquid flow will not cause the vibration of the pipeline, which fundamentally eliminates the noise source.

(2) When the hydraulic cylinder moves longitudinally, the noise source at the pressure oil inlet is caused by the throttle plug. Because after the system flow increases, the running speed of the whole machine is too fast, which has a great influence on the fuselage when starting and stopping. In order to reduce the speed properly, a throttle plug is added (see figure 1). When pressure oil enters the hydraulic cylinder through orifice a-a and port B, a jet is formed due to the sudden increase of orifice area. Thereby generating strong impact noise.

(3) The cross-sectional area of the middle part of the combined channel B is the smallest (but it can meet the throttling requirements), and the liquid inlet A and outlet C are both made into horns. The installation test has achieved satisfactory results and eliminated this noise source.

(4) In order to avoid noise, the abrupt change of flow section should be avoided as far as possible in the liquid flow pipeline; When steel pipes are used, especially when there are many bends, the influence of hydraulic pressure should be considered to avoid the vibration phenomenon in the pipes. If necessary, a section of hose can be added to eliminate vibration and prevent noise.

Hydraulic static pile driver consists of hydraulic lifting mechanism, hydraulic clamping device, pile driver (jack), walking and slewing mechanism, hydraulic and power distribution system, counterweight iron, etc. Working principle: the walking device consists of "transverse walking" (short boat), "longitudinal walking" (long boat) and slewing mechanism.

Working characteristics of static pile driver

Compared with hammer pile driver and vibration pile driver, it has no impact force, can avoid the pile head from breaking and bursting, and has a small disturbance range to the soil around the pile when pressing the pile, which can improve the construction quality of pile foundation, save pile materials and reduce the project cost. No vibration, noise and environmental pollution, suitable for construction in densely populated cities. However, pile pressing is limited to vertical pile pressing and pile sinking construction in soft soil foundation, which has certain limitations.

The working principle of hydraulic static pile driver is to use its own weight and counterweight to press precast piles into the soil. In the construction of precast pile, hydraulic static pile driver can adopt compaction and driving methods, precast pile construction machinery is one of the methods of precast pile construction, hydraulic static pile driver adopts compression method, and diesel hammer, steam hammer and hydraulic hammer adopt penetration method. The mechanized construction method of single pile has its shortcomings and limitations. Static pressure pile is only suitable for the construction of soft soil foundation because of its own mechanical weight (compressive strength) limitation.

When the formation is weak, the pile hammer can't jump when the formation is weak, so turn off the diesel hammer. Therefore, it is inefficient to use diesel hammer in soft soil, and there are public hazards such as waste gas and noise. When the hydraulic impact hammer is driven, its impact force directly acts on the pile top, which is easy to damage the pile body and the fuselage is high. Therefore, when using hydraulic impact hammer to pile, the reinforcement rate of pile driving must be high, which increases the pile driving cost. Because hydraulic impact is often used in the whole piling process, it is easy to damage various parts of hydraulic hammer, reduce the sealing performance of hydraulic hammer and shorten the service life of hydraulic hammer. Hydraulic static pile driver has the advantages of no vibration, low noise, safety and stability, high efficiency and reliable piling quality. It can know the bearing data in time, move and walk more freely, and the frame structure combination is more reasonable, which is convenient for installation, disassembly, migration and transportation.

The pile pressing method adopted in the invention not only has low cost, but also saves steel bars and concrete. Hydraulic static pile driver not only has low noise and pollution, but also has little influence on surrounding vibration and interference to surrounding environment. Suitable for soft soil environment, widely used in urban construction, especially for pile foundation engineering in dense buildings and urban centers, and often used in the expansion projects of some factories.

Structure description of hydraulic static pile driver: Hydraulic static pile driver is a construction pile driver composed of oil inlet system, hydraulic static pressure system, clamping mechanism and hydraulic power system. The hydraulic system consists of accumulator, pressure relay, stop valve, bidirectional four-way solenoid valve, pile barrel, impact barrel and hammer head. The oil inlet and oil return channels of the oil inlet system are respectively connected with the oil inlet and oil return channels of the pile barrel. The impact cylinder is a closed structure, and the piston is provided with an axial small hole. It is not only suitable for the construction of soft and hard foundation, but also suitable for the construction of soft and hard foundation.

The traditional pile driver consists of pile hammer, pile frame and auxiliary equipment. The pile hammer of the static pressure pile driver is connected to two parallel vertical guide rods (commonly known as gantry) at the front end of the pile frame and lifted by a hook. The pile frame is a steel tower, and the rear part of the pile frame is provided with a hoist for lifting piles and pile hammers. There are two guide rods in front of the pile frame to control the piling direction, so that the pile can be accurately driven into the stratum according to the design direction. The basic technical parameters of pile driver are impact offset, impact kinetic energy and impact frequency. According to different power sources, pile hammers can be divided into drop hammers, steam hammers, diesel hammers and hydraulic hammer.

In the construction of precast pile, hydraulic static pile driver can adopt compaction and driving methods, precast pile construction machinery is one of the methods of precast pile construction, hydraulic static pile driver adopts compression method, and diesel hammer, steam hammer and hydraulic hammer adopt penetration method. The mechanized construction method of single pile has its shortcomings and limitations. Static pressure pile is only suitable for the construction of soft soil foundation because of its own mechanical weight (compressive strength) limitation.

Static precast pile of hydraulic static pile driver is mainly used in soft soil foundation and general clay foundation. In the process of pile pressing, the pile driver's own weight (including compressive strength) is used as the reaction force to overcome the pile side friction and pile end resistance in the process of pile pressing. The precast pile sinks into the soil under the vertical static pressure, and the soil around the pile is squeezed rapidly and violently, and the pore water pressure of the soil rises sharply, and the shear strength of the soil decreases greatly, which makes the pile sink rapidly. It is an ideal equipment for modern pile foundation engineering.