阅读说明：本技术 一种水泥砂搅拌桩施工方法 (Construction method of cement sand mixing pile ) 是由 黄琦 方宏彬 林楚涛 方春亮 苏曼琪 黄维阳 郑淳淳 张天翼 李方远 詹旭晨 方 于 2019-10-21 设计创作，主要内容包括：本发明涉及一种水泥砂搅拌桩工艺施工方法,在常规单、双、三轴水泥搅拌桩桩机的基础上,通过在桩架上加焊排砂管固定架从而固定D100加砂管,加砂管后接机制砂砂池,尾端接空气压缩机,水泥搅拌桩桩机第一次向下搅拌至设计标高时,启动空气压缩机后通过D100加砂管向桩位处喷出钻杆杆径平方数的0.3倍的体积的机制细砂,以匀速提升、喷水泥浆,边提升边由搅拌叶片将水泥浆、土体及细砂混合搅拌,边提升边喷浆,直至提升到设计桩顶高程以上0.3～0.5m,即完成二喷二搅。本发明机制细砂配合水泥搅拌桩搅拌作用,形成具有一定强度及塑性的水泥砂桩体,能够有效提高成桩后桩体强度及成桩后的地基承载力。(The invention relates to a cement sand mixing pile process construction method, on the basis of a conventional single, double and three-shaft cement mixing pile machine, a sand discharge pipe fixing frame is additionally welded on a pile frame to fix a D100 sand adding pipe, a sand making sand pool is connected after the sand adding pipe, the tail end of the sand making sand pool is connected with an air compressor, when the cement mixing pile machine is firstly mixed downwards to a designed elevation, the air compressor is started, machine-made fine sand with the volume of 0.3 times of the diameter square number of a drill rod is sprayed out to a pile position through the D100 sand adding pipe, cement paste is lifted and sprayed at a constant speed, cement paste, soil and fine sand are mixed and stirred by a mixing blade while being lifted, and the cement paste is sprayed while being lifted until the height of the top of the designed pile is lifted to be 0.3-0.5m above the elevation, so that the two-spraying two-. The machine-made fine sand is matched with the stirring action of the cement stirring pile to form a cement sand pile body with certain strength and plasticity, and the strength of the pile body after pile forming and the bearing capacity of a foundation after pile forming can be effectively improved.)

1. The construction method of the cement sand mixing pile is characterized by comprising the following construction steps in sequence: the method comprises the following steps of site leveling, pile placing position measurement, pile frame welding and sand discharge pipe of the pile machine, sand pool connection pump machine and sand discharge pipe, pile stirring machine alignment, pre-stirring sinking and guniting, sand conveying of the sand discharge pipe, four-stirring and four-spraying construction of the stirring pile to the designed depth and displacement.

2. The cement sand mixing pile construction method according to claim 1, characterized in that: the used fine sand is machine-made fine sand, the fineness modulus is 2.2-1.6, and the average grain diameter is 0.35-0.25 mm.

3. The cement sand mixing pile construction method according to claim 1, characterized in that: the volume of fine sand used by the single pile is 0.3 square of the cross section area of the diameter of the pile.

4. The cement sand mixing pile construction method according to claim 1, characterized in that: the cement used for construction is general cement, namely ordinary portland cement or slag portland cement or pozzolanic portland cement or fly ash portland cement or composite portland cement.

5. The cement sand mixing pile construction method according to claim 1, characterized in that: the cement mixing pile frame is additionally welded with a sand discharge pipe fixing frame, the sand discharge pipe is fixed at the fixing frame on the pile frame, and the tail end of a machine-made sand pool is connected with an air compressor behind the sand discharge pipe.

6. The cement sand mixing pile construction method according to claim 1, characterized in that: when the cement mixing pile driver downwards mixes to the designed elevation for the first time, the air compressor is started, machine-made fine sand with the volume 0.3 times of the diameter and the square number of the drill rod is sprayed to the pile position through the D100 sand adding pipe, the pumping pressure of the air compressor is 0.3MPa, the machine-made fine sand stays for 30s after the sand is added, the machine-made fine sand is lifted and sprayed at a constant speed, the grouting pressure is kept at 0.4-0.6MPa, the cement paste and the soil body are mixed by the mixing blades while being lifted, the cement paste is sprayed while being lifted until the height of the pile top is 0.3-0.5m above the designed pile top, and the secondary spraying secondary mixing is completed.

Technical Field

The invention relates to the technical field of mixing pile construction, in particular to a cement sand mixing pile construction method.

Background

In our country, the cement mixing pile technology is generally applied to treating various soft soil foundations as a mature soft foundation treatment technology. The existing process method closest to the scheme of the invention comprises the following implementation flows: leveling the site → positioning the pile driver, checking whether the machine meets the requirement, operating normally → checking the pile position → checking the verticality of the pile driver → checking the density of cement slurry → mixing and sinking for guniting → lifting guniting for guniting → repeated mixing and sinking for guniting → lifting repeated guniting for guniting → finishing 4 mixing and spraying to the leveling elevation → sealing the pile head with cohesive soil → shifting the pile driver, and constructing the next pile.

The prior technical scheme has the following defects and reasons: firstly, the four-stirring four-spraying process consumes longer time and is not suitable for projects with shorter construction periods, and secondly, if the geological conditions to be treated are poorer and the sludge layer is thicker, the pile forming quality of the stirring pile is negatively influenced.

From the above, if the fine sand is added in the construction process, the geological conditions at the pile position of the soft foundation treatment can be optimized, so that the coagulation speed of the cement mixing pile can be ensured, and the pile forming quality can be ensured to meet the design requirements. Therefore, the method has very important significance for projects with short construction period and strict requirements on the pile forming quality of the mixing pile.

Disclosure of Invention

The invention aims to solve the technical problem of overcoming the defects of the prior art and provides a construction method of a cement sand mixing pile.

In order to solve the technical problems, the technical scheme provided by the invention is as follows: a construction method of a cement sand mixing pile comprises the following construction steps in sequence: the method comprises the following steps of site leveling, pile placing position measurement, pile frame welding and sand discharge pipe of the pile machine, sand pool connection pump machine and sand discharge pipe, pile stirring machine alignment, pre-stirring sinking and guniting, sand conveying of the sand discharge pipe, four-stirring and four-spraying construction of the stirring pile to the designed depth and displacement.

Furthermore, the used fine sand is machine-made fine sand, the fineness modulus is 2.2-1.6, and the average grain diameter is 0.35-0.25 mm.

Furthermore, the volume of fine sand used by the single pile is 0.3 square of the cross section area of the diameter of the pile.

Furthermore, the cement used for construction is general cement, namely ordinary portland cement or slag portland cement or pozzolanic portland cement or fly ash portland cement or composite portland cement.

Furthermore, a sand discharge pipe fixing frame is additionally welded on the pile frame of the cement mixing pile, the sand discharge pipe is fixed at the position of the fixing frame on the pile frame, and the tail end of the sand making sand pool is connected with an air compressor after the sand discharge pipe is connected.

Further, when the cement mixing pile driver downwards mixes to the designed elevation for the first time, machine-made fine sand with the volume 0.3 times of the diameter and the square number of the drill rod is sprayed to the pile position through the D100 sand adding pipe after the air compressor is started, the pumping pressure of the air compressor is 0.3MPa, the machine-made fine sand stays for 30s after the sand is added, the machine-made fine sand is lifted and sprayed at a constant speed, the grouting pressure is kept at 0.4-0.6MPa, the cement paste and the soil body are mixed by the mixing blades while being lifted, the machine-made fine sand is sprayed while being lifted until the machine-made fine sand is lifted to 0.3-0.5m above the designed pile top elevation, and the two-spraying and two-.

The invention has the following advantages: compared with the existing cement mixing pile construction technology, the invention mainly welds the sand discharge pipe on the pile frame, and the sand discharge pipe is connected with the air pump and the sand pool. When the pile rod is pre-stirred, sunk and gunited, fine sand in the sand pool is sucked by an air pump and pumped into the pile position through a sand discharge pipe. And the four-stirring and four-spraying operation is carried out while the grouting pressure is kept, so that the cement slurry and the fine sand are fully mixed, the pile forming quality of the pile foundation is improved, and the age of pile body consolidation is shortened. The invention has the advantages that the fine sand and the fine sand volume experiments with different grain diameters can be carried out according to different engineering geological conditions, so as to screen out the fine sand type and the doping volume which have the highest economic efficiency and cost performance. The method aims to improve pile-forming quality, shorten construction period and save construction cost. Machine-made fine sand is added in the construction process of the cement mixing pile to replace undisturbed soil, and the fine sand, cement paste and the undisturbed soil are mixed and stirred to form a pile body with certain strength and bearing capacity. Can improve the strength, integrity and uniformity of the pile body in a limited way.

Drawings

FIG. 1 is a flow chart of a construction process of a conventional cement mixing pile.

FIG. 2 is a flow chart of the cement mixing pile construction process of the present invention.

Fig. 3 is a schematic view of the construction of the cement mixing pile of the present invention.

Detailed Description

The present invention will be described in further detail with reference to examples.

If the construction area is in an underground area with boulders or local hard rock, before the cement-sand mixing pile driver is in place, hole guiding operation can be carried out through a hydraulic walking type long spiral drilling machine, and the hole guiding depth is 1.5-2.5 m.

Before the construction begins, the D100 sand discharge pipe is fixed at a fixed frame on a pile frame by welding, and the tail end of a machine-made sand pool is connected with an air compressor behind the sand discharge pipe.

When the cement mixing pile driver downwards mixes to the designed elevation for the first time, the air compressor is started, and machine-made fine sand with the volume 0.3 times of the square number of the diameter of the drill rod is sprayed to the pile position through the D100 sand adding pipe, the pumping pressure of the air compressor is 0.3MPa, the machine-made fine sand stays for 30 seconds after sand is added, the machine-made fine sand is lifted and grouted at a constant speed, and the grouting pressure is kept at 0.4-0.6 MPa. And (3) stirring the cement paste and the soil body by the stirring blade while lifting, and spraying the cement paste while lifting until the cement paste is lifted to be 0.3-0.5m above the designed pile top height, thus completing the secondary spraying and secondary stirring.

The fine sand used in the invention is machine-made fine sand, the fineness modulus is 2.2-1.6, and the average grain diameter is 0.35-0.75 mm; the machine-made fine sand is aired for 1-2 days before being put into production, so that the water content in the sand is reduced, and the probability of pipe blockage of a sand discharge pipe in the pumping process of the fine sand is reduced. Aiming at complex geological conditions, the fine sand with the grain diameter of 0.35-0.5mm has the best effect, the strength of the pile body can be improved in a limited way, the holes are easily filled with the fine sand in the grain diameter range, and the pile forming strength of the stirring pile improves the integrity and uniformity of the pile body. The sand filling rate in the hole is 50-90%, and through multiple field tests, the sand filling rate in the hole reaches more than 50%, so that the quality of the pile is obviously improved.

The invention takes the first-stage project of municipal infrastructure in the violin zone of the central business area of the Zhuhai Cross door, namely bridge engineering (a violin bridge), as an example, the soft foundation treatment of the project adopts cement sand mixing piles with the diameter of 600 and the pile length of 9.4m for construction.

The single pile construction comprises the following raw materials in parts by weight:

572.4kg of cement

151.2kg of sand

298.9kg of water

Before formal construction, a DN100 sand adding pipe is fixed by additionally welding a sand discharge pipe fixing frame on a cement mixing pile frame, a sand making sand pool (the grain diameter of the machine-made fine sand in the sand pool is 0.35-0.5mm) is connected after the sand adding pipe, and the tail end of the sand making sand pool is connected with an air compressor. When the cement mixing pile driver downwards mixes to the designed elevation for the first time, an air compressor is started and then an air compressor is used for ejecting 0.3 times of the square number of the diameter of a drill rod to the pile position through a D100 sand adding pipe (namely 600 x 0.3 mm)³＝0.108m³) The machine-made fine sand with the volume of (1) is prepared, the pumping pressure of an air compressor is controlled to be 0.3MPa, the sand is added and stays for 30 seconds, then the sand is lifted at a constant speed, the slurry is sprayed, and the grouting pressure is kept at 0.4-0.6 MPa. While lifting, the stirring blade can stir cement paste, soil and fine materialsAnd (4) mixing and stirring the sand, and spraying the slurry while lifting until the height of the designed pile top is 0.3-0.5m higher, thus completing four-spraying and four-stirring.

Under the same experimental conditions, the 28-day core-pulling strength, the 90-day core-pulling strength and the composite foundation bearing capacity of the example are compared with those of the original mortar base, and the results are as follows:

performance index	The concrete sand pile body of the example	Cement pile body
			28 days core pulling strength	0.75Mpa	0.46Mpa
Core pulling strength of 90 days	2.25Mpa	1.97Mpa
			Bearing capacity of 28-day composite foundation	113Kpa	100Kpa

Through the example contrast, can see when taking cement sand mixing pile to carry out soft foundation and handle, enough volume and the appropriate fine sand of particle diameter are sent into through the air compressor pump in the stake position department after leading the hole machine to lead the hole, can ensure that the pile-forming effect of cement mixing pile reaches design and standard requirement, and is favorable to accelerating cement mixing pile rate of setting, and the bearing capacity in later stage has obtained the improvement.

Although the invention has been described in detail hereinabove with respect to a general description and specific embodiments thereof, it will be apparent to those skilled in the art that modifications or improvements may be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.