**1. Introduction**

With the rapid development of expressway construction, in China, construction on soft ground is sharply increasing, such as Shen-Jia-Hu Expressway that passes through soft soil [1,2]. Owing to shortened construction periods and to the rheological properties of soft soil, among other reasons, the embankment after settlement of many highways opened abroad is too high, which does not meet relevant regulatory requirements (i.e., post-construction should be less than 30.0 cm) [3]. The post-construction settlement of expressways has become a major type of expressway damage, which will not only seriously affect the vehicle's road speed, traffic safety, and driving comfort, but also seriously affect the stability and safety of the highway itself [4–6].

In order to reduce post-construction settlement, the embankment is replaced with light soil to reduce the overburden load and control the settlement [7,8]. At present, the widely used light soils mainly include EPS beads-mixed lightweight soil, EPS block, and foamed cement banking, which include good integrity, light mass, and convenient construction. The lightweight soil's cohesion, global strength, bulk density, and other parameters can be adjusted by adjusting the output of cement and foam [9]. The advantages and disadvantages of various methods are shown in Table 1. Foamed cement banking research is already well underway in numerous countries [10–12], and some results have been achieved in practice. Compared with other materials, the FCB has a shorter construction period, lower curing time, and higher construction quality, thus it has broad application prospects [13,14]. As FCB's bulk density is only conventional soil bulk density of 1/4 to 1/8, its use as a replacement of embankment material [15–17], can not only reduce the base load pressure, but can also reduce the total settlement and differential settlement [18]. Replacing the undisturbed soil with lightweight soil to process the post-construction settlement of

**Citation:** Wu, Y.; Liu, H.; Liu, J. Use of Foamed Cement Banking for Reducing Expressways Embankment Settlement. *Appl. Sci.* **2021**, *11*, 11959. https://doi.org/10.3390/ app112411959

Academic Editors: Daniel Dias and Bing Bai

Received: 14 October 2021 Accepted: 13 December 2021 Published: 15 December 2021

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expressway under traffic control seriously affected highway traffic operations. Especially, there are no closed roads (ramps) during construction, the lightweight soil is being put down to achieve subgrade compactness, that causes huge economic losses due to the road closure.

**Table 1.** Comparison of different lightweight fills.


In this paper, foamed cement replacement is carried out on both sides of the embankment, which does not affect the normal traffic operation during replacement construction, its use is targeted and flexible, and only small settlement occurs after improvement. Combined with Shen-Jia-Hu EK0 + 323 highway section, this paper verifies the advantages of FCB in dealing with embankment settlement without road closure. Through the analysis of dynamic monitoring data of Shen-Jia-Hu expressway's subgrade settlement, and according to the proportional relationship between settlement and load, the calculation method of embankment replacement thickness is proposed, which can be applied to complex construction processes, this work can thus provide a reference for similar future projects.
