Volume 7, Issue 2 June 2022

Case-History

Steel sheet pile earth retaining wall in flood control work
(Jinan City, China)
Yunxiang Wang
Shanghai Office, GIKEN LTD.

Hongjuan He
Secretariate, IPA
In recent years, with the progress of global warming, abnormal weather such as intense heat, heavy rain, typhoons andhurricanes have frequently occurred in various countries around the world. China is no exception, and last year, in 2021,
they suffered severe flood damage in Henan Province, which is located in the central part of China, with a record heavy
rainfall. As awareness of disaster prevention increases, the number of projects where the press-in piling method isadopted is increasing in disaster prevention and mitigation works where disaster countermeasures are urgently needed.
This paper introduces a case of temporary earth retaining work to improve drainage function as part of flood control
measures carried out in Jinan City, Shandong Province.

1. Project Overview
The main content of the whole project is the new construction ofa box culvert. The location of this work is in Jinan City, ShandongProvince, China (Fig. 1). Jinan City is located in the western part of
Shandong Province and occupies an important position in termsof business and administration as a provincial capital. The Yellow
River flows through the city and is vulnerable to floods caused byheavy rains. In 2020, the roads in the construction section of theproject were flooded due to a strong typhoon, which caused many
inconveniences to the movement and livelihoods of residents inthe area, and also caused economic damage in some areas. The
Jinan City Government decided to renovate the drainage system
to solve the inundation problem in this section.

Jinan city

Google MapFig. 1. The Map of Jinnan CityAs shown in Fig. 2, the total length of the entire construction section will be about 1,200 m, and the construction started
in January 2021 and will be completed in September 2022. Since there are many residential areas and factories in theconstruction area, it was necessary to make arrangements for half road closures and detours and so on.

RailroadStartProjectOffice

Fig. 2. The map of construction site area
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Volume 7, Issue 2 June 2022
The press-in piling work in this project is the construction of a temporary retaining wall accompanying the new
construction of a box culvert. The press-in piling method combined with the water jetting was adopted, and it wasconstructed with U-shaped steel sheet piles (pile lengths 9m and 12m) using the press-in piling machine F111.

2. The Press-in Piling WorkAs mentioned above, this site is a densely populated area with houses and factories, and it was required that it would
not affect the surrounding economic activities during the construction period as well as vibration and noise should beminimized during the piling work. In addition, preliminary research had revealed that the underground buried utilities
and building waste were mixed in the ground. For the above reasons, the press-in piling method was recognized as themost suitable method, and it was decided to adopt it for the project. In addition, since the soil was clay, the construction
method combined with the water jetting was adopted.
The challenge for this construction was to pay close attention to the surrounding environment during the construction.
As shown in Fig. 3, the existing utility poles and high-voltage lines are in close proximity to the steel sheet pile work line
at the construction site. When a crane was used to lift the 12m and 9m long steel sheet piles, careful consideration wastaken to keep sufficient distance from the high-voltage lines.

High-voltage line

Telephone poleFig. 3. The view from above
Fig. 4 is a photograph taken during the construction in proximity.
As shown in the photo, there were many construction sites close
to the existing structures in this case. Since the press-in pilingmachine is more compact than a general pile driver, it waspossible to do the installation work in the minimum space evenin a narrow site between an adjacent structure and a steel sheet
pile retaining wall. Since the ground vibration and noise during
construction were extremely small compared to theconventional construction methods that require impact andvibration, the construction was able to be carried out safely
without significantly affecting the surrounding environment.

Fig. 4. Construction in proximity

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Volume 7, Issue 2 June 2022
3. Press-in assisted with water jetting method
According to the Handbook1), Press-in assisted with water jetting method which was adopted in this project, as shown inFig. 5, is a pressing technique where water jetting is used as a driving assistance. Piles are installed while injecting highpressure water into the ground from a nozzle that is fitted onto the pile toe to reduce penetration resistance (toe resistance,shaft resistance). Press-in assisted with water jetting has the following three advantages.
 The water pressure generates an increase in pore water pressures associated with a decrease in effective
stresses around the toe of the pile, resulting in a decrease in shear resistance of the soil.
 The upward water flow generated along the interface between the pile and the surrounding soil spreads theeffect of reduced effective stresses and reduces shaft friction between the soil and the pile.
 Prevents the soil clogging inside interlocks, which reduces the frictional resistance between interlocks.
In this work, steel sheet piles to be used for temporary work were used. As mentioned in the previous newsletter (Vol,6.4), used sheet piles are often used for temporary steel sheet pile retaining walls in China. By using a water jetting
together, the press-in/extraction force can be optimized, the damage to the steel sheet pile is minimized, and thus futurereuse is possible.

Fig. 5. The image of press-in assisted with water jetting method1)

4. Summary
In disaster prevention works in urban areas, it is often difficult to secure a large work space, and there are generally many
restrictions on construction conditions. By means of the press-in piling method, we were able to reconfirm the usefulnessof maintaining the functions of surrounding facilities, minimizing vibration and noise, and performing safe and secureconstruction at this site. In China, the development of disaster prevention infrastructure is being promoted intensively,
and it is expected that the press-in piling method will be more activated in the future.
References
1) International Press-in Association (IPA) (2021) Press-in Retaining Structures: A Handbook Second, Edition, 2021, 200p.

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