The Institute of Foundation Engineering of the China Academy of Building Research was established in 1953. It primarily serves various geotechnical engineering projects in national construction and urban development, is dedicated to solving key technical problems in engineering, is responsible for drafting and managing major foundation engineering technical standards and codes, and conducts common, fundamental, and public-benefit technical research required in the field of foundation engineering.

In accordance with the requirements of the China Association for Engineering Construction Standardization's "Notice on Issuing the Second Batch of Association Standard Formulation and Revision Plan for 2022" (Jianbiao Xie Zi [2022] No. 77), Jianyan Foundation Engineering Co., Ltd., as the lead drafting unit, is responsible for drafting the "Technical Specification for Composite Anchor Anti-Uplift Piles" (hereinafter referred to as the "Specification"). The inaugural meeting of the drafting group was successfully held in Beijing on September 18, 2023, in a combined offline and online format. The meeting was chaired by the Foundation Engineering Professional Committee of the China Association for Engineering Construction Standardization, and more than 30 people attended, including the chief editor of the "Specification" and members of the drafting group from the participating units.

Photo 01: Meeting site photo one

Researcher Gao Wensheng, Chairman of the Foundation Engineering Professional Committee, delivered a speech and introduced the situation of engineering construction standardization reform. At the inaugural meeting of the drafting group, the list of drafting units and drafting group members of the "Specification" was read out, the establishment of the drafting group of the "Specification" was announced, and the specific requirements for the drafting work of the Specification were explained.

Photo 02: Meeting site photo two

At the first working meeting of the "Specification," chief editor Researcher Yao Zhiquan introduced the purpose, significance, and preliminary preparation work of drafting this "Specification," and proposed arrangements for the division of labor among drafting group members, the drafting schedule, and detailed special research. In conjunction with the requirements for drafting engineering construction standards, the participating experts fully discussed the outline of the "Specification" and the grouping of drafting group members, and put forward supplementary and revision opinions. Experts from all participating units reached a consensus and all stated that they would complete the drafting work according to the schedule.

Photo 03: Some experts attending the meeting online

Photo 04: Group photo of experts attending the on-site meeting

Appendix:

Technical introduction related to the "Technical Specification for Composite Anchor Anti-Uplift Piles"

Academician Qian Qihu of the Chinese Academy of Engineering gave an incisive description of civil engineering: "The nineteenth century was the century of bridges, the twentieth century was the century of skyscrapers, and the twenty-first century is the century of underground space." In recent years, the development and construction of various underground spaces has been in full swing, but when the groundwater level is high, the development and construction of underground space is inevitably affected by groundwater, among which how underground structures resist the buoyancy of groundwater is a relatively common problem.

The commonly used measures to solve the anti-uplift problem of underground structures mainly include the water buoyancy release method, the counterweight increase method, and the installation of anti-uplift components such as anti-uplift piles or anti-uplift anchors. Among these, installing anti-uplift components such as anti-uplift piles or anti-uplift anchors is the most commonly used method to solve the anti-uplift problem of underground structures. In addition, when some tall structures are subjected to large horizontal loads, their foundations also have anti-uplift problems, and anti-uplift components such as anti-uplift piles or anchors are often used. Installing anti-uplift components such as anti-uplift piles or anti-uplift anchors is the most commonly used method to solve foundation anti-uplift and foundation pull-out problems. However, ordinary anchors have defects such as low bearing capacity and high cost. Moreover, under working conditions, the pile concrete or grout body of ordinary anti-uplift piles and anti-uplift anchors is in a tensile state. Because the tensile strength of concrete or grout is low, cracks are likely to appear in the pile concrete or anchor grout body when subjected to tension. In addition, because the protective layer of the load-bearing steel bars is thin, the load-bearing steel bars in the anti-uplift components will be eroded by groundwater and gradually corroded, reducing the tensile bearing capacity, and in severe cases may cause the load-bearing steel bars to be pulled apart and render the anti-uplift components ineffective.

At present, engineering solutions to such problems generally start from the following aspects:

1. The stress state of anti-uplift piles and anti-uplift anchors can be changed, and prestressing technology can be used to change the stress state of the pile or anchor from tension to compression, effectively reducing the occurrence of cracks and improving the service life of the steel bars;

2. Anti-corrosion treatment can be applied to the steel bars or protective measures can be added, which can also improve the service life of the steel bars;

3. The amount of reinforcement in anti-uplift piles and anchors can be increased to control crack width, but this method does not give full play to the strength of the steel bars and causes great waste of steel.

In response to the problems and defects of current conventional anchors and anti-uplift piles, Jianyan Foundation Engineering Co., Ltd. has developed a new type of anti-uplift component—composite anchors and composite anchor anti-uplift piles—that simultaneously has the advantages of high anti-uplift bearing capacity, full utilization of steel bar strength, good durability, fast construction speed, simple construction operation, suitability for a wide range of strata, and the ability to apply prestress.

Composite anchors and composite anchor anti-uplift piles are new foundation engineering technologies developed by Jianyan Foundation Engineering Co., Ltd. based on the academy's 2013 basic research project "Research on Several Issues of Anti-Uplift Components." This technology has obtained two national patents: one invention patent (a construction method for a concrete shaft composite anchor, patent number ZL201510360640.8) and one utility model patent (a concrete shaft composite anchor, patent number ZL201520446623.1).

Composite anchors and composite anchor anti-uplift piles can be used for foundation anti-uplift and pull-out structures of buildings (structures), municipal engineering, underground engineering, and tall structures in construction projects. Composite anchors and composite anchor anti-uplift piles have strong adaptability to geotechnical conditions and are suitable for both various soil foundations and rock foundations. Composite anchors and composite anchor anti-uplift piles have the following characteristics:

(1) The anti-uplift bearing capacity is higher than that of ordinary anchors of the same length.

The hole diameter of composite anchors and composite anchor anti-uplift piles is generally 300 mm to 600 mm, which is 2 to 3 times that of ordinary anchors, and the total side resistance of the foundation soil is far greater than that of ordinary anchors of the same length.

(2) The load-bearing steel bars are completely isolated from corrosive media.

The outer side of the load-bearing steel bars of composite anchors and composite anchor anti-uplift piles is a steel pipe with a closed bottom. The wall thickness of the steel pipe is determined according to the corrosion rate, ensuring that the load-bearing steel bars are completely isolated from corrosive media during the design service life.

(3) The waterproofing structure between the anchor and the foundation is reliable and simple.

The steel pipe of composite anchors and composite anchor anti-uplift piles extends into the foundation by no less than 150 mm. The waterproof layer can be coated and adhered to the surface of the steel pipe, and a water-stop steel plate can also be welded onto the steel pipe to form a second line of defense. The waterproofing method is simple and the waterproofing quality is reliable.

(4) High cost-effectiveness.

The engineering cost of composite anchors and composite anchor anti-uplift piles is 60% to 80% of that of ordinary anchors or anti-uplift piles.

(5) High construction efficiency.

The construction of composite anchors and composite anchor anti-uplift piles can adopt the long spiral drilling and pressure-grouted concrete process. For composite anchors and composite anchor anti-uplift piles with a length of 10 m to 20 m, one drilling rig can construct 20 to 40 units per shift.

(6) Good environmental performance.

Composite anchors and composite anchor anti-uplift piles can be constructed with long spiral drilling rigs, with no mud pollution, and they save steel or cement compared with ordinary anchors and anti-uplift piles.

Composite anchor and composite anchor anti-uplift pile technology has been applied in more than ten foundation anti-uplift projects in Beijing, Guangdong, Hainan, Hebei, Liaoning, Yunnan, and other places, with an output value of over 100 million yuan, saving tens of millions of yuan in foundation engineering investment for construction units, and achieving good economic, social, and environmental benefits.