CN112593879A

CN112593879A - Forced circulation method for foundation construction slurry

Info

Publication number: CN112593879A
Application number: CN202011540823.5A
Authority: CN
Inventors: 朱忠民; 刘令军; 陈砚祥; 汪志雄; 夏磊; 卢俊哲; 陈燕涛
Original assignee: Hunan Dingsheng Foundation Engineering Co ltd
Current assignee: Hunan Dingsheng Foundation Engineering Co ltd
Priority date: 2020-12-23
Filing date: 2020-12-23
Publication date: 2021-04-02

Abstract

The invention discloses a forced circulation method of foundation construction slurry, which comprises the following steps: the method comprises the following steps of adopting a slurry circulating conveying system consisting of a drilling hole, a sedimentation tank, a slurry tank and a slurry pump, and adjusting the concentration of slurry in the drilling hole when the pile foundation drilling construction is carried out, so that a water head inside and outside a steel casing is kept in a pressure balance state at a certain height difference; pumping the slurry with the slag in the steel casing into a sedimentation tank, pumping the slurry with the slag into a slurry tank after sedimentation, pumping the slurry into a drilling hole from the slurry tank, and performing circulating operation until the drilling of the formed hole is completed. The invention is characterized in that 1, when the pile foundation is drilled, the slurry with high specific gravity is adopted to ensure that the water heads inside and outside the steel casing keep a certain height difference in a pressure balance state, thereby effectively preventing the slurry leakage phenomenon; 2. the mud is conveyed by the mud circulating conveying system in the drilling process, and the method is simple, convenient and reliable.

Description

Forced circulation method for foundation construction slurry

Technical Field

The invention belongs to a foundation construction method, and particularly relates to a forced circulation method of foundation construction slurry.

Background

The slurry leakage phenomenon often occurs in foundation construction such as bridge construction in deep water pile group construction with few or even no covering layer, and the fact that the steel casing can not be embedded into the covering layer or the bedrock is deep enough is the main reason of slurry leakage due to the fact that the riverbed covering layer is shallow or has no covering layer. The slurry leakage phenomenon seriously affects the construction quality and progress, and an effective treatment method is required to be found.

Disclosure of Invention

The invention aims to provide a slurry leakage prevention treatment method for drilling construction of deep water piles with few covering layers of bridges and with a good slurry leakage prevention effect.

The technical scheme for realizing the purpose of the invention is as follows:

the invention provides a forced circulation method of foundation construction slurry, which comprises the following steps: the method comprises the following steps of adopting a slurry circulating conveying system consisting of a drilling hole, a sedimentation tank, a slurry tank and a slurry pump, and adjusting the concentration of slurry in the drilling hole when the pile foundation drilling construction is carried out, so that a water head inside and outside a steel casing is kept in a pressure balance state at a certain height difference; pumping the slurry with the slag in the steel casing into a sedimentation tank, pumping the slurry with the slag into a slurry tank after sedimentation, pumping the slurry into a drilling hole from the slurry tank, and performing circulating operation until the drilling of the formed hole is completed.

And the concentration of slurry in the drilled hole is 1.20-1.40 during the construction of the drilled hole of the pile foundation.

And after the pile foundation is formed into a hole, placing the mud pipe to the bottom of the drilled hole which is formed into the hole, and cleaning the hole.

The concentration of the slurry after cleaning the drilled hole is 1.05-1.12.

Has the advantages that:

the method of the invention is characterized in that:

1. when the drilling construction of the pile foundation is carried out, the high-specific gravity slurry is adopted to ensure that the water heads inside and outside the steel casing are kept in a certain height difference and in a pressure balance state, so that the slurry leakage phenomenon can be effectively prevented;

2. the drilling process adopts a mud circulating conveying system consisting of a drilling hole, a sedimentation tank, a mud tank and a mud pump to convey mud, and the method is simple, convenient and reliable.

The method is suitable for slurry leakage treatment of the underwater pile foundation, and is also suitable for foundation construction of various onshore piles requiring slurry circulation operation in areas with complex terrains, such as mountains with complex terrains, cliffs and other occasions.

The invention is further described below with reference to the accompanying drawings.

Drawings

FIG. 1 is a schematic diagram of a mud circulation system used in the present invention.

Detailed Description

Referring to fig. 1, the forced circulation method of foundation construction slurry provided by the invention comprises the following steps:

a sedimentation tank 7 and a mud pit 8 are arranged on a pile foundation construction site, a plurality of mud pumps are arranged on a construction platform 6, one mud pump 5 is used for pumping mud in the mud pit 8 into a drilling hole 9 in a steel casing 2, one mud pump 3 is used for pumping mud with slag in the drilling hole 10 into the sedimentation tank 8, the other mud pump 4 is used for pumping the mud precipitated in the sedimentation tank 7 into the mud pit 8, and the drilling hole 9, the sedimentation tank 7, the mud pit 8 and the

mud pumps

3, 4 and 5 form a mud circulating conveying system;

when the drill bit 1 of the drilling machine is used for drilling a hole in a pile foundation, adjusting and keeping the concentration of slurry in the drilling hole 9 to be 1.20-1.40, and keeping a certain height difference between the water head inside and the water head outside the steel casing 2 in a pressure balance state; the mud with slag in the steel casing 2 is pumped into a sedimentation tank 7, the mud with slag is pumped into a mud tank 8 after sedimentation, and then is pumped into a drilling hole 9 through the mud tank, the circulation operation is performed until the hole forming drilling is completed, after the pile foundation is formed, a mud pipe 10 needs to be placed at the bottom of the drilled hole 9 with the formed hole, so that the hole cleaning work can be completed better, the mud concentration after the hole cleaning is 1.05-1.12, and finally, concrete is poured to form the pile foundation.

The principle of the method is that the internal and external water heads of the cylinder are in a pressure balance state by adjusting the concentration of the slurry, and the slurry leakage is prevented by utilizing the balance state.

Examples of the applications

The foundation of each pier of the 16# -20# pier of the Henan Hederan Yuan water four-bridge main bridge is designed into 75 bored piles with 15 D2.2m. The pile foundation is a rock-socketed pile, the pile length is 20.5-49 m, and the maximum design square amount of single pile foundation concrete is 196m 3. And (3) formally starting the underwater pile in 2015, and erecting an overwater steel pipe pile foundation construction platform, wherein the platform construction area of each pier is 27m multiplied by 18 m. The designed construction water level is 30.0m, the elevation of the top surface of the platform is higher than the designed construction water level by 2.5m and is 32.5m in consideration of the influence of construction and flood, and a high pile beam plate structure is adopted. The platform foundation adopts phi 800 multiplied by 6 steel pipe piles, and the upper structure adopts a profile steel structure; the type of the drilling machine is a percussion drill, the hole forming process is a positive circulation hole forming process of the percussion drill, and a vibration hammer is adopted to insert and beat a long steel casing (the steel casing penetrates through a covering layer for 3 meters or until a rock stratum, and the diameter of the steel casing is 2.55 m).

The phenomenon of slurry leakage occurs in the front and back of the construction of the pile foundation in the engineering water, wherein the construction difficulty is the largest with the No. 17 pier, and the slurry leakage frequency is the largest. Particularly, the pile foundation of the No. 17 pier A-5 is positioned on a riverbed with a small covering layer, the covering layer of the riverbed is about 1.2m, the vibration depth of the steel casing is 1.1m, and analysis shows that the steel casing cannot be embedded into the river to a sufficient depth, which is a main reason for slurry leakage.

A-5, slurry leakage occurs on the third day of drilling of the pile foundation, the initially adopted treatment method is to add clay and flaky stones, and the flaky stones and the clay are beaten by using a normal drilling stroke to enter a bottom opening of the steel casing through gravity extrusion of a drill bit so as to fill gaps of the bottom opening of the steel casing to achieve the effect of leakage stoppage; after 3 times of repeated addition of clay and rubble, leakage cannot be stopped; because the construction period is short, the leakage can be stopped for many times without any effect. Secondly, determining to perform secondary downward vibration on the steel casing, simultaneously determining the slurry leakage position at the bottom of the steel casing by using underwater camera equipment and a diver, backfilling a sand bag outside the steel casing, adding loess after backfilling the sand bag, and performing secondary drilling until the slurry still leaks when the steel casing is drilled to the bottom of the steel casing; in contrast, the bottom of the steel casing is sealed by a method of pouring mortar by pouring underwater concrete, the steel casing is placed for 36 hours after mortar is poured, the drill is started again after the mortar reaches a certain strength, slurry leakage occurs after the drill drills for 3 hours, the original drill bit is replaced, and a drill bit with the diameter of 2.45m is used for reaming and drilling so that the steel casing meets the rock embedding requirement; vibrating the steel casing after drilling, vibrating the steel casing to rock embedding depth, adding clay and adding bagged cement (5: 2) layer by layer, wherein the adding height exceeds 5m of the bottom of the steel casing, after the adding, a drilling machine uses a small stroke to extrude and mix the clay and the bagged cement, then a heavy hammer is put lightly to stir the clay and the cement uniformly to form cement-soil slurry, stopping the drilling machine for 12 hours, drilling the steel casing after the cement-soil slurry is precipitated and filled in gaps, and then slurry leakage occurs again after the drilling is started, wherein the slurry leakage lasts for about 30 minutes and stops when the slurry leakage reaches about 3m below the horizontal plane, the slurry leakage phenomenon and result analysis shows that the slurry leakage is small gap leakage at the bottom opening of the steel casing, and through research and discussion, the clay and other objects cannot be added into the steel casing, if the slurry leakage is added, large slurry leakage is likely to be caused again, so the method is decided to adopt high specific gravity to balance the pressure inside and outside the steel casing, finally, the method is used for drilling to a final hole, and the smooth concrete pouring is realized.

Claims

1. A forced circulation method of foundation construction slurry is characterized by comprising the following steps: the method comprises the following steps of adopting a slurry circulating conveying system consisting of a drilling hole, a sedimentation tank, a slurry tank and a slurry pump, and adjusting the concentration of slurry in the drilling hole when the pile foundation drilling construction is carried out, so that a water head inside and outside a steel casing is kept in a pressure balance state at a certain height difference; pumping the slurry with the slag in the steel casing into a sedimentation tank, pumping the slurry with the slag into a slurry tank after sedimentation, pumping the slurry into a drilling hole from the slurry tank, and performing circulating operation until the drilling of the formed hole is completed.

2. The forced circulation method of foundation construction slurry according to claim 1, wherein the slurry concentration in the drilled hole during the drilling of the pile foundation is 1.20 to 1.40.

3. The forced circulation method of foundation construction mud according to claim 1 or 2, wherein after the pile foundation is bored, the mud pipe is placed at the bottom of the bored hole to be bored, and the hole is cleaned.

4. The forced circulation method of foundation construction slurry as claimed in claim 3, wherein the concentration of the slurry after hole cleaning of the drilled hole is 1.05-1.12.