Development of Hydraulic Jack Needs Close Combination with Steel Industry

Development of Hydraulic Jack Needs Close Combination with Steel Industry            

The hydraulic jack sets up a partition wall in front of the equipment pipe of the whole cutting type tunneling machine to form a sealed cabin. The sealed cabin is usually filled with mud, the fluidity of the flutter slurry is maintained, the cutting disc rotates in the mud, and strong stirring is applied. The cut soil is mixed with mud water and a new kind of mud is discharged by mud pump or hydraulic hoist. On the other  hand, the pressure water is continuously supplemented. In the sealed cabin, the mud pressure and the vertical upward pressure and water pressure on the upper working face are maintained equally to maintain the stability of the working face. This method is called mud pressure method.            

The mud-water pressure method has a wide ventilation boundary occasionally, and can be jacked in multi-water, fluid and liquefied soils. The mechanized pollution degree is more directional, the  pipe space is large and easy to operate, and the front correction jack can also  be swindled to Jack in order to overcome the relative elongation of the head  resistance, safe operation and no "gas collapse" phenomenon. But when  the sludge can not be directly removed, it needs to be treated separately, which increases the cost; poor sealing will lead to leakage problems, such as the short length of pipe joints, water supply and drainage pipelines must be disassembled and assembled every time the pipe is removed.            

The construction cost of Jack freezing method is high. Usually only when drainage or grouting method is ineffective can it be used. When the permeability coefficient of soil reaches 1-5 m/day, it is not suitable to adopt the method of mining and aging. If the soil water content is less than 1065, the freezing strength is not easy to meet the requirements. On the contrary, the freezing heave of the upper layer occurs during the freezing process. When the ice is thawed, the volume of the ice is compacted and the ground subsides. Because of the high cost of freezing method, it is seldom used in pipe jacking construction, even if it is only used as a temporary emergency response.           
 Fasteners are one of the most common basic components in a large number of fields, which are closely related to the steel industry at all levels. Feng Jinyao, president of the Fasteners Association of China General Machinery Parts Industry Association, analyzed the development trend of the fastener industry in China and the demand for steel products. The basic circuit in the hydraulic jack system is a typical circuit which uses hydraulic components as working medium and can complete specific performance. According to the performance, it can be divided into target control loop, pressure control loop, speed control loop and sequential behavior loop.           
 It means that the manufacture of fasteners may be steel, non-ferrous metal, stainless steel, titanium alloy or other engineering raw materials, and the processing method may be hot-working and cutting. However, more than 90% of the fasteners are processed by cold heading agent. The products manufactured by this process are of high precision, good quality and high production efficiency. China's fastener industry maintains continuity. Five years of steady double-digit growth. Although China is a big fastener country at  present, its annual output is expected to be 5 million tons per year, and its annual consumption of steel is controlled by 6 million tons. However, the development of cold heading steel for fasteners is relatively late, and the types and specifications of steel for fasteners are few, which can not meet the domestic demand and export of fasteners.           
 Over the years, China's economic development in has maintained an 8% growth rate, bringing good opportunities to the development of fastener industry. The recovery of the world's economy has increased at an even rate of 4%. This has also brought business opportunities to the development of fastener industry. The rise of manufacturing level of China's fastener enterprises is inseparable from the increase of fastener raw materials and new cold heading raw materials. The development of fastener industry can not be separated from the support of iron and steel industry. As long as they establish excellent cooperation, fastener industry and steel industry will achieve better development.