## 1 Introduction  
In municipal infrastructures, it is usually necessary to construct a small, temporary, shallow shaft, such as a working shaft, for pipe jacking and pipe maintenance [1, 2]. These temporary shafts are generally supported by reinforced concrete structures, which include reinforced concrete cairasons, diaphragm walls, row piles, shotcrete and steel arch frame supports [3, 4, 5, 6, 7]. The disadvantages of these methods include a long duration for concrete curing [8, 9], high costs, complicated construction procedures, environmental pollution [10], and resource waste [11, 12], due to unrecyclable components. [PERSON] et al. [13] proposed that sustainable and consumption reduction construction technology is an important development direction for the future.  
In recent years, recyclable and prefabricated supporting structures and technologies have been proposed to solve these problems. Steel sheet piles and jet-grouted columns with H steel piles have been widely applied to foundation pits [14, 15, 16, 17]. Steel sheet piles and soil mixing walls can solve the problem of construction pollution and material recovery to some extent, but there are still some limitations in engineering applications [18]. For example, the large machinery needed for sinking and the loud noise and water pollution caused by cement means that it is not suitable for construction in high-density city areas that require strict environmental protection and small sites [19, 20]. Additionally, some researchers [21, 22] have provided several suggestions for supporting small shafts. [PERSON] et al. [21]designed a spiral supporting structure, which was prefabricated in a factory and assembled on site within the shaft. [PERSON] et al. [22] developed a spiral supporting structure and proposed a design approach. These authors verified the convenience, reliability, recyclability and effectiveness of this new supporting structure through field tests. Excavation and support are carried out simultaneously with this technology, which is suitable for urban construction, due to its low noise. However, this structure utilizes the passive stress structure method, which plays a role after soil deformation. This passive support method can induce the further development of deformation in surrounding soil [23; 24], especially in soft soil, where the deformation is greater. Therefore, these structures are inapplicable to the conditions of soft soil, loose soil, and areas where deformation control is very strict. Prestressed supporting structures, such as prestressed anchor cables and prestressed internal supports, can satisfactorily solve these problems. However, this supporting structure's prestress is applied at discrete points, which unevenly distributes the stress along the supporting structure.  
To overcome such drawbacks, in this study, a novel prestressed supporting structure was designed to support small shafts. The construction of this structure was carried out via on-site assembly. Field tests were carried out to study the support effect of the novel structure. Field measurements of earth pressure, structure stress, and lateral displacement were collected to study the variation characteristics of the prestress during the construction process.