*3.1. Engineering Situation*

The practical site for experiments was part of the Zhejiang Shenjiahua Hangzhou Expressway (Lianhang Section) project (hereafter referred to as the Shen-Jia-Hu expressway), which is located on Hang-jia-hu plain, the geographical location of Shen-Jia-Hu is shown in Figure 2. This region has a developed economy, high population density, and high transportation requirements. However, the numerous lakes and rivers cause a large amount of soft soil in this region. Most of its road sections pass through soft soil foundation, which contain soils characterized by high moisture content, high compression, low strength, and low permeability, which will cause greater road settlement.

In view of the engineering geological conditions, in addition to conventional improvement methods such as grout spray pile (pile diameter 500.0 mm, 3.05 million linear meters) and prestressed concrete pipe pile (pile diameter 400.0 mm, wall thickness 60.0 mm, 590 thousand linear meters), Shen-Jia-Hu expressway also adopted equal preloading (2.39 million m3) along the whole line. The expressway subgrade was filled with earthworks mixture. The foundation improvement mainly adopted stacking load precompaction and combined the plastic wick drain. The road section chosen for experiments is the EK0 + 323 ramp bridge road, which has a 10 m wide pavement, a 3.25 m high embankment, and a 1:1.5 slope grade. The soil cohesion and internal friction angle were obtained through direct shear experiment, and the soil water content was obtained through the oven-drying method. The other parameters and specific steps were determined according to the Standard for geotechnical testing method [3], and the parameters are given in Table 2. It should be noted that the soil parameters were obtained after the surcharge preloading method. The cohesion values were relatively higher than other soil.

**Figure 2.** Geographic position of Shen-Jia-Hu expressway.


