摘 要 河北省沿海、内陆平原及山区都广泛分布有软土，其含水量高、孔隙比大、渗透性小、压缩性高、抗剪强度低的工程性质给高速公路的建设带来了十分不利的影响。特别是随着2020年河北省高速公路发展布局规划的展开，软土工程问题越来越成为制约高速公路发展的关键问题。 本文以河北省沿海高速公路沧州段软土地基为研究对象，建立起该段软土地基物理力学性质指标相关方程。在此基础上，本文对该软土地基进行了稳定性计算，并对不满足要求的路段进行旋喷桩地下连续墙处理。同时，本文利用FLAC3D数值模拟软件，分析了该路段在填筑期和运营期的稳定性以及水和地震对其稳定性的影响。通过以上研究，可以得到以下几点结论： （1）通过对沿海高速公路进行了稳定性计算，路堤系数在1.127～1.666之间。为保证路堤的安全使用，拟定安全系数F＞1.3。对不满足公路稳定性要求的部分路段，采用旋喷桩地下连续墙进行加固处理。 （2）在公路填筑期和运营期，地下连续墙的存在会引起墙内外侧土体应力的重分布，能够有效的防止地基土层的沉降与侧向滑动。同时地下连续墙对土体蠕变有一定的抑制作用，因而能够提高地基承载力，保证路堤填筑与公路运营的安全。 （3）地下水对软基作用主要表现为地基物理力学性质降低以及渗流对路堤稳定性的影响。但是由于连续墙透水性差，地下水渗流时需要绕过连续墙。同时地震活动会大幅度的降低地基安全性能，从而使路基遭受破坏。因而修建路堤时需要考虑地下水以及地震的影响。

ABSTRACT Soft soil widely distributed in coastal wetlands, inland plain and mountain area in Hebei Province, which brought bad affect for freeway construction as its <font color='red'>engineering</font> geological properties of high water content, high void ratio, low permeability, high compressibility and low shear strength. Especially with the planning of freeway development layout in Hebei Province in 2020 is beginning, soft soil <font color='red'>engineering</font> is becoming the key problems of constrained freeway development. The Cangzhou section soft soil foundation of coastal freeway in Hebei Province is studied in this paper, and the correlation equation of physico-mechanical properties indexes in this soft foundation is established. On this basis, the stability of soft foundation is calculated and the sections which don’t meet the stability requiremet are controled by diaphragm wall. At the same time, the stability of the coastal highway sections in filling stage and operation are calculated and the influence of water and earthquakes are analysised. The following conclusions can be obtained through the above research: (1) The stability factor of embankment is between 1.127～1.666 from stability calculation about coastal freeway. To ensure the safe use of embankment, the safety factor is F>1.3. The sections which don’t meet the stability requiremet are controled by diaphragm wall. (2) The existence of diaphragm wall can cause redistribution of stress in internal and external side soil, which can effectively prevent the foundation soil settlement and lateral sliding in filling stage and operation. At the same time, the diaphragm wall has certain inhibitory effect for soil creep, where it could improve the foundation capacity and ensure the safe of embankment filling and operation. (3) The influence of groundwater on the soft ground are physico-mechanical properties indexes of soft foundation is reduceing and the seepage has bad impact on embankment stability. However, due to the poor permeability of diaphragm wall, N the seepage need to bypass the diaphragm wall. Seismic activity will also greatly reduce the safety performance of the foundation, so that the foundation would be destroyed. Thus the construction of embankment and groundwater need to be considered when the impact of the earthquake.