A method for predicting deformation during the excavation of a foundation pit in composite formation is proposed. The artificial bee colony algorithm (ABC) is introduced to optimize the back-propagation (BP) neural network with the input variables filtered. This method is applied to predict the deformation of a foundation pit project. The prediction results are verified by comparing the results with those of other neural network models. The results indicate that the depth of excavation, speed of excavation, friction angle in the soil, gravity, elastic modulus and number of internal support layers are the main factors affecting the deformation of the soil layer around the foundation pit. The ABC algorithm is capable of searching for better solutions of initial weights and thresholds. The ABC-BP model with a 6-12-2 network structure has high prediction accuracy and the best generalization ability.

The coastal area of Fujian Province in China is rich in both sea sand and sea mud. However, sea sand and sea mud are both unsuitable as direct filler materials for seawalls due to their poor geotechnical properties. To turn waste into a useful product, a mixture composed of sea sand and sea mud is proposed as a filler material for seawalls. The strength, compressibility, moisture sensitivity, and permeability of the mixture are investigated experimentally. The results show that when the mass ratio of sea sand to limed sea mud is 1:2, the mixture exhibits good engineering properties and can serve as a filler material for general engineering purposes in dry environments. To apply the mixture under saturated conditions, both cement and lime are used to improve the engineering properties of the mixture. The improvements in the properties increase with both the binding agent content and the curing time, and the improvement with the addition of cement to the mixture is better than that with the addition of lime. The engineering requirements of seawalls can be satisfied by adding cement, and the cement content can be chosen according to considerations of the construction period and engineering costs.

The application of polymer flocculants plays a pivotal role in the slurry separation process of shields, and the dispersant used for treating cutter mud cakes can significantly impact the effectiveness of polymer flocculants, potentially leading to reduced efficiency in slurry separation. Experiments were conducted to select appropriate flocculants and investigate the influence of dispersants on flocculant effectiveness, aiming to assess the effect of flocculants and explore the relationships and mechanisms governing their influence. Changes in the patterns of slurry flocculation were revealed in terms of flocculation-driven precipitation and vacuum-filtration effects. The purpose of this article is to provide a reference for the field application of polymer flocculants in the shield field. The conclusions are as follows. Inorganic flocculants containing 0.5% polyaluminum chloride (PAC) exhibit the most effective flocculation, demonstrating strong charge neutralization action. Organic flocculants containing 0.1% cationic polyacrylamides (CPAM) exhibit the most effective flocculation, demonstrating strong bridging and net capture effects. The dispersant sodium hexametaphosphate (SHMP) can significantly weaken the charge-neutralizing action of flocculants and slightly enhance bridging and net capture effects. SHMP can impede the flocculation of slurry with PAC. For CPAM, SHMP can enhance the flocculation of slurry at a low mass fraction (0.1% and 0.3%), while SHMP can significantly hinder flocculation at a high mass fraction (0.5% and 1%). A low mass fraction of SHMP reduced slurry viscosity to 246.3 mPa.s and enhanced vacuum filtration, while a high mass fraction of SHMP increased slurry viscosity to 667.2 mPa.s and hindered vacuum filtration. In conclusion, while dispersants reduce the effectiveness of inorganic flocculants at any mass fraction, a small number of dispersants enhances the performance of organic flocculants; thus, the organic flocculant CPAM is recommended for slurry separation.

An interesting operation has been developed to estimate the critical normalized surface settlement for shallow tunnels in undrained clay (idealized as a homogeneously Tresca material). The upper-bound finite-element method in combination with a plastic-dissipation-based mesh adaptive strategy is used to obtain upper-bound solutions and velocity fields. Based on the vertical velocity field, the corresponding critical surface settlement field is obtained by introducing an assumed constraint related to soil deformation. The results show that the critical normalized surface settlement pattern is similar to a plug with concentrated strain at the bottom, and the calculated settlement data are fitted well by superimposing two Gaussian curves. The widths of the main settlement trough and the plug increase with increasing dimensionless unit weight γD/c, and the plug-type settlement pattern is easily recognized with an increase of dimensionless depth H/D. For different combinations of H/D and γD/c, a new normalized equation is developed to evaluate the critical normalized surface settlement. The results agree reasonably well with the solutions reported in the literature.