【Excerpt】What is the difference between cement mixing pile and high pressure jet pile?

What is the difference between high pressure jet grouting pile and cement mixing pile?

        There are several main aspects: different working principles, different machines used, different construction techniques, different applicable soil layers, and different specific uses.

First, the principle is different

        1、Cement mixing pile Deep cement mixing pile uses cement as the main agent of curing agent, and through specially designed deep mixing machinery, the soft soil and curing agent are forced to mix on site in the deep foundation, so that the soft soil hardens and the foundation strength is improved.

        This method is suitable for the treatment of soft soil, and the treatment effect is remarkable. After treatment, it can be put into use quickly. In terms of construction methods, according to the state of the reinforcement materials used, it can be divided into two types of construction: slurry mixing method (wet method, that is, deep cement slurry mixing method) and powder mixing method (dry method).

        2、High-Pressure Jet Grouting Pile A high-pressure jet grouting pile uses a drilling rig to insert a grout pipe with nozzles into the predetermined position in the soil layer. The grout is then ejected in a high-pressure stream from the nozzle, impacting and disrupting the soil. The high-pressure stream cuts and disintegrates the soil layer, which becomes granular. Part of it is carried out of the borehole by the grout and water, while the other part mixes with the grout. As the grout mixes and is stirred, the grout pipe continuously rotates 360 degrees. As the grout solidifies, it forms a structure with certain strength and impermeability.

        In terms of construction methods, single pipe method, double pipe method and triple pipe method can be used respectively; in terms of injection forms, there are three kinds: rotary injection, fixed injection and swing injection.

Second, different machines

        1、Cement mixing pile PH-5 series deep mixing pile machine and corresponding auxiliary equipment (slurry pump, slurry mixer and other cement slurry preparation equipment).

        2.High pressure jet pile, jet pile machine, high pressure plunger pump, air compressor, slurry mixer, grouting pump, sewage pump and other equipment.

Third, different processes

        1、Cement mixing pile: Pile position layout → Positioning of drilling rig → Inspection and adjustment of drilling rig → Positive circulation drilling to the designed depth → Turn on the high-pressure grouting pump → Reverse circulation to lift the drill and spray cement slurry → 0.3m below the working benchmark level → Repeat mixing and drilling with cement slurry to the designed depth → Reverse circulation to surface → Pile completion → Proceed to the next pile.

        2、High-pressure jet grouting pile Position layout of the pile → positioning of the drilling rig → lead hole (expansion hole) to the design elevation → blocking the vertical nozzle → mixing slurry → rotating and spraying from bottom to top to the design top → flushing → moving the pile.

Fourth, the applicable soil layer and use are different

        1、cement mixing pile: cement mixing pile is suitable for the treatment of normal consolidation of silt and silty soil, plain fill soil, powder soil, clay and loose sand soil without flowing groundwater. The reinforcement depth is generally more than 5.0m.

        According to the engineering geological conditions of the site, the load requirements of the superstructure and the stress state of cement soil piles, the cement soil reinforced body formed by deep mixing piles can be used as retaining walls for foundation pit engineering, waterproof curtains; vertical bearing composite foundations; large volume cement-stabilized soil, etc.

        The shape of deep mixing reinforcement can be categorized into columnar, wall-like, grid-like, and block-like forms. Among these, the columnar form is commonly used for composite foundations in soft soil reinforcement; the wall-like and grid-like forms are primarily used as retaining walls and waterproof curtains for deep foundation pit excavation; the block-like form is often applied to the foundations of structures with high unit area loads and strict requirements for controlling uneven settlement.

        2、High-pressure jet grouting piles: High-pressure jet grouting piles are suitable for treating layers of silt, silty soil, plastic flow, soft plastic or plastic cohesive soil, plain fill soil, silty soil, sand, and gravelly soil. However, when the soil layer contains a large amount of coarse gravel, numerous plant roots, or significant organic matter, and if the groundwater flow rate is too high, their use should be cautious or determined based on site test results. The reinforcement depth is generally greater than 5.0m.

        Spiral jet grouting piles (reinforcement bodies) can be used for foundation reinforcement of existing and new buildings, soil layer reinforcement or waterproofing in deep excavations, and subway projects. In excavation support engineering, they are often used alone as anti-seepage curtain walls in the form of fixed or swinging jets, or in conjunction with anti-seepage piles (inter-pile directional swinging jets) to serve as anti-seepage retaining walls.

        In conclusion, the reinforcement effect of cement-soil mixing and high-pressure jet grouting is the same, both involving the mixing of cement, soil, and water to form a reinforced body. Compared to cement-soil mixing, high-pressure jet grouting has higher efficiency and broader applicability, although it is also more expensive. In the reinforcement of soil at shield tunnel entrances, cement-soil mixing is primarily used, while high-pressure jet grouting is employed for gaps that cannot be reinforced between the reinforced body and the underground diaphragm wall.

——Source: New youth, engineering data clerk

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