CN1137594A - Method for manufacturing expanding concrete pile - Google Patents

Abstract

The manufacturing method of expanded concrete pile is as follows: according to the designed requirements, firstly, the strength grade of concrete to be used is defined according to the manufacturing process of general concrete pile, i.e. the weight ratio of all ingredients including cement, water, sand and broken stone is defined. On this basis a concrete expanding agent whose weight is 5%-30% of that of cement is added, then all ingredients are uniformly stirred, and filled in the pile hole by layers with vibrating and compacting until its designed standard height is reached. Said method is simple and easy to implement.

Description

A kind of preparation method of expansive concrete stake

The present invention relates to the concrete pile technical field of cast-in-site.

At present, concrete and reinforced concrete pile have become built the base form that high-rise building, heavy factory building and the various building that specific (special) requirements arranged extensively adopt on the bad grounds of soil property.But because the ordinary concrete properties of materials, tangible shrinkage is arranged in course of hardening, and shrinkage factor increases along with the prolongation of time, the concrete made of high standard cement especially, cement consumption is many more, and shrinkage factor is also big more.Because concrete contraction, make and produce small gap between stake and the peripheral soil, when water content is big in the periphery soil of stake hole, the gap is also big more, and particularly moisture as producing lubrication, certainly will cause the bearing capacity of stake obviously to descend between stake and peripheral soil, along with building growth or the maneuvering load increase of service life, when settling amount value of being above standard of stake, will produce the factor that is absolutely unsafe to the superstructure of building, thereby can shorten the application life of building.U.S.'s US3504497 patent has proposed a kind of method of making concrete pile of expansive cement, but the shortcoming that concrete pile was difficult to overcome of making of expansive cement is, can not guarantee the intensity of pile body with the concrete of expansive cement stirring, can not reach again according to the ground soil property, the void content that soil layer is different, water content and the expansion rate of designing requirement, though it proposes to adopt a kind of constraint mechanism (promptly using pertusate gunnysack or pipe fitting) to control the size of expansion force, but this is difficult to accurately control in practice of construction, thereby this method is not widely adopted in pile foundation engineering always.Cement expansive material (UEA) is that China Building Materials Academy finished experimental study in 1985, the new material that the nineties begins to go into operation, be mainly used in seepage control and crack resistance, secondary pouring, seam and repairing work field at present, adopt cement expansive material making concrete pile and reinforced concrete pile not to see as yet that so far report is arranged.

Of the present invention day is that a kind of new method of making concrete pile at engineering site will be provided, both can guarantee the intensity of pile body with the concrete pile of this method making, can overcome the ordinary concrete stake again and reduce the drawback of bearing capacity, and can also significantly improve the frictional force between stake and the peripheral soil of stake because of the sclerosis contraction.

Technical scheme of the present invention may further comprise the steps:

A, according to designing requirement, according to the preparation method of general concrete pile, determine to select for use concrete strength grade, promptly determine the weight ratio of cement, water, sand, stone each component;

B, on the basis of above-mentioned each component proportioning, add the cement expansive material of cement weight 5%-30%;

C, above-mentioned each component mixed by weight ratio mix thoroughly, layering is filled in the hole, and filler limit, limit vibration compacting is until design elevation.

The concrete consumption of cement expansive material can be determined by following method among the present invention: according to stake footpath D, the compression modulus Es i of each soil layer of stake periphery soil, the adhesion stress factor alpha i of each soil layer of stake periphery soil, the additional bearer power P that stake periphery each soil thickness hi of soil and designing requirement increase is attached, according to formula Calculate the lateral expansion rate S of stake,, determine the weight ratio of cement expansive material and ordinary Portland cement then in conjunction with the performance of ordinary concrete self shrinkage factor and cement expansive material.

The used Strength of Common grade of the present invention is C20-C60, and used cement is above Portland cement or slag cements of label 425#.As in the stake hole, being placed with cage of reinforcement, adopt said method of the present invention to can be made into the stake of reinforcing bar expansive concrete.

Advantage of the present invention is: it guarantees concrete strength of pile by ordinary Portland cement, stone, sand, satisfy the expansion rate of void content, water content and the designing requirement of different foundation soils with the consumption of adjusting cement expansive material, operation is simple, and expansion force is convenient to control.Owing in concrete, contain expansion agent, in the hydration and hardening process of stake, form a large amount of expansion crystalline solid, As time goes on and constantly this expansion crystalline solid grows up, adhesion, producing concrete under its pressure expands, stake periphery soil is formed extruding, produce around the normal pressure of pile body vertical direction.Under the effect of this normal pressure, make the additional friction power that has produced between pile body and peripheral native wall except that the frictional resistance of ordinary concrete stake, improve the bearing capacity of stake greatly, thereby can prolong building application life.The present invention can save about 15% of similar pile foundation engineering cost, and can improve work efficiency, the reduction of erection time, is adapted to make each.Type friction pile, the friction hold the stake, the explosive expansion friction pile.

Under become by embodiment the present invention be further described.

Example 1, certain complex building, Floor 12,9000 square metres of building areas, high 51.86 meters, frame construction, base form is a pile foundation, adopts the spiral drilling machine pore-forming, stake footpath D=0.7 rice, stake is long 18 meters, and stake is placed cage of reinforcement in the hole.

Geological conditions: farinose argillic horizon, moisture content W=27.4%, void ratio e=0.57, compression modulus Es=8.0MPa, adhesion stress factor alpha=0.5, the permission frictional resistance is 40KPa, it is 600KPa that the stake end allows bearing capacity, the bearing capacity of ordinary concrete stake is 1800KN, designing requirement increase additional bearer power be P attached=30KN.

At first according to designing requirement, press the preparation method of ordinary concrete stake, determine that concrete strength grade is C30, promptly the weight ratio of cement, water, sand, stone each component is: 425# slag cements: water: sand: stone=385: 190: 609: 1220;

The lateral expansion rate that calculates stake should be: $\mathrm{\ΔS}=\frac{30\×{10}^3}{3.14\×0.7\×8\×10^6\×0.5\×18}=1.9\×{10}^{-4}$ With ordinary concrete self shrinkage factor is 3 * 10 ^-4Meter, then Zhuan overall expansion rate should be: (3+1.9) * 10 ^-4=4.9 * 10 ^-4, determining the cement expansive material consumption according to the performance of expansion agent thus is 5% of cement weight.With above-mentioned each component mixing and stirring in proportion, its mixing time prolongs one minute than ordinary concrete, and layering is inserted in the hole then, and filler limit, limit vibration compacting until design elevation, is made the stake of reinforcing bar expansive concrete.

Example 2:

One office building, eight layers, 4500 square metres of building areas, high 30.8 meters, frame construction, the basis forms pile foundation, adopts the auger boring pore-forming, stake footpath D=0.6 rice, stake is long 12 meters.

Geological conditions: first floor is a silty clay, water content W ₁=15.5%, void ratio e ₁=0.57, modulus of compressibility E _S1=12.9MPa, sticking lacquer force coefficient α ₁=0.3, thickness h ₁=4 meters, permission frictional resistance is 35KPa; The second layer is a clay, water content W ₂=16.7%, void ratio e ₂=0.623, modulus of compressibility E _S2=13.3MPa, the adhesion stress factor alpha ₂=0.3,10 meters of thickness, then this layer thickness of stake periphery h ₂=8 meters, allow frictional resistance 30KPa, it is 500KPa that the stake end allows a bearing capacity, the ordinary concrete pile capacity is 850KN, designing requirement increases additional bearer power P attached=150KN.Then Zhuan making step is:

Determining strength grade of concrete according to the preparation method of ordinary concrete stake is C20;

The lateral expansion rate that calculates stake should be: $\mathrm{\ΔS}=\frac{150\×{10}^3}{3.14\×0.6(12.9\×{10}^6\×0.3\×4+13.3\×{10}^6\×0.3\×8)}$

=1.68 * 10 ^-3By ordinary concrete self shrinkage factor is 0.3 * 10 ^-3, then Zhuan overall expansion rate should be 1.98 * 10 ^-3, according to the performance of cement expansive material, the consumption of determining expansion agent thus is 15% of a cement weight, then the weight ratio of each component is:

425# portland cement: water: sand: stone: cement expansive material

=1: 0.59: 1.9: 3.7: 0.15 with above-mentioned each component mix is even in proportion, vibration compacting in the hole is inserted in layering, reaches design elevation and gets final product.

Example 3:

With another group stake of above-mentioned example 2 same engineerings, stake footpath D=0.6 rice, stake is long 15 meters, and first and second layer soil layer, the stake end is in the 3rd layer of soil layer in example 2, and the 3rd layer is lam, water content W ₃=19.8%, void ratio e=0.687, modulus of compressibility E _S3=6.4MPa, the adhesion stress factor alpha ₃=0.4,18 meters of soil thickness allow frictional resistance 40KPa, and it is 600KPa that the stake end allows bearing capacity, then each layer thickness h of stake periphery soil ₁=4m, h ₂=10m, h ₃=1m, the bearing capacity of ordinary concrete stake are 1050KN, determine that according to this strength grade of concrete is C40, and designing requirement increases additional bearer power P attached=400KN is by formula

Calculating the horizontal swollen of stake should be with rate $\frac{400\×{10}^3}{3.14\×0.6(12.9\×{10}^6\×0.3\×4+13.3\×{10}^6\×0.3\×10+6.4\×{10}^6\×0.4\×1)}$ =3.7 * 10 ^-3Self shrinkage factor of ordinary concrete is 0.3 * 10 ^-3, then Zhuan overall expansion rate should be 4 * 10 ^-3, determining its consumption according to the performance of cement expansive material thus is 25% of cement weight, if select 525# cement for use, then the weight ratio of each component is: 525# cement: water: sand: stone: cement expansive material=1: 0.44: 1.2: 3: 0.25.Mix is even in proportion with above-mentioned each component, and layering is inserted in the hole, and the vibration compacting while inserting reaches design elevation.

Claims (5)

1. the preparation method of an expansive concrete stake is characterized in that may further comprise the steps:

A, according to designing requirement, according to the preparation method of ordinary concrete stake, determine to select for use concrete strength grade, promptly determine the weight ratio of cement, water, sand, stone each component;

B, on the basis of above-mentioned each component proportioning, add the cement expansive material of cement weight 5%-30%;

C, above-mentioned each component mixed by weight ratio mix thoroughly, layering is filled in the hole, and filler limit, limit vibration compacting is until design elevation.

2,, it is characterized in that the consumption of cement expansive material is determined by following method according to the preparation method of the described expansive concrete stake of claim: according to stake footpath D, the compression modulus Es i of each soil layer of stake periphery soil, the adhesion stress factor alpha of each soil layer of stake periphery soil _i, each soil thickness h of stake periphery soil _iAnd the additional bearer power P that designing requirement increases is attached, according to formula:

Calculate the lateral expansion rate Δ s of stake,, determine the weight ratio of cement expansive material and ordinary Portland cement then in conjunction with the performance of ordinary concrete self shrinkage factor and cement expansive material.

3, the preparation method of expansive concrete stake according to claim 1 and 2 is characterized in that the Strength of Common grade is C20-C60.

4, the preparation method of expansive concrete stake according to claim 3 is characterized in that it is above Portland cement or slag cements of 425# that cement adopts label.

5, the preparation method of expansive concrete stake according to claim 1 is characterized in that being placed with cage of reinforcement in the stake hole, makes the stake of reinforcing bar expansive concrete.