To the aim of this paper is to study the structural and environmental deformation characteristics caused by the excavation of a very large deep foundation pit in the sandy soil area of Beijing. This paper is based on numerical simulation and field monitoring results and these results are compared with the deformation data of a soft soil foundation pit in the Shanghai area. The results show that the influence of the environment surrounding the super-large deep foundation pit project studied in this paper is obviously too great. With the progress of construction, the deformation rate and deformation amount of the column at the side of the foundation pit are obviously higher than that of the column in the middle area. Due to the hysteresis of stress transfer in the sand, the settlement of the roof of the north wall is delayed and the deformation range is smaller than that of the south wall. Compared with the conventional foundation pit, the influence area of the surrounding surface is larger, reaching 4 He (He is the depth of the foundation pit). Delta vmax (the maximum surface settlement) is between 0.2 similar to 2.3% He, and the relationship between delta vmax = 1.43% Vwm. Through orthogonal experiments and numerical simulation, it is concluded that the deformation of foundation pit structure and its surrounding environment is more sensitive to excavation unloading, precipitation amplitude, and column spacing. It is also concluded that the strong, medium, and weak influence areas of the bottom uplift after foundation pit construction are (0 similar to 0.07) x L, (0.07 similar to 0.14) x L, and (0.14 similar to 0.5) x L, respectively (L is the width of foundation pit). When the embedment ratio is between 1.8 similar to 2.4, the displacement mode of the parapet structure is T mode; when the embedment ratio is between 2.4 similar to 3.4, the displacement mode of the parapet structure is RB mode.

In deep foundation pit engineering, the soil undergoes a complex stress path, encompassing both loading and unloading phases. The Shanghai model, an advanced constitutive model, effectively accounts for the soil's deformation characteristics under these varied stress paths, which is essential for accurately predicting the horizontal displacement and surface settlement of the foundation pit's enclosure structure. This model comprises eight material parameters, three initial state parameters, and one small-strain parameter. Despite its sophistication, there is a scarcity of numerical studies exploring the correlation between these parameters and the deformation patterns in foundation pit engineering. This paper initially establishes the superiority of the Shanghai model in ultra-deep circular vertical shaft foundation pit engineering by examining a case study of a nursery circular ultra-deep vertical shaft foundation pit, which is part of the Suzhou River section's deep drainage and storage pipeline system pilot project in Shanghai. Subsequently, utilizing an idealized foundation pit engineering model, a comprehensive sensitivity analysis of the Shanghai model's multi-parameter values across their full range was performed using orthogonal experiments. The findings revealed that the parameter most sensitive to the lateral displacement of the underground continuous wall was kappa, with an increase in kappa leading to a corresponding increase in displacement. Similarly, the parameter most sensitive to surface subsidence outside the pit was lambda, with an increase in lambda resulting in greater subsidence. Lastly, the parameter most sensitive to soil uplift at the bottom of the pit was also kappa, with an increase in kappa leading to more significant uplift.

In order to solve the problem of low comprehensive utilization rate of industrial solid waste, this article focuses on the three problems of slag, which are steel slag, reuse of silica fume, and the strength enhancement and microscopic mechanism of slag-steel slag-silica fume composite material; analyzes the macro strength of the mixture under different curing ages from the two indexes of unconfined compressive strength and splitting tensile strength; and conducts microscopic tests such as X-ray diffraction, scanning electron microscopy, and Fourier transform infrared. The internal mechanism of hydration product formation and strength change of slag and steel wollastonite cementitious material under the excitation of sodium hydroxide and sodium silicate mixed solution as alkali activator was discussed. The strength results show that when the optimum mixture ratio of slag: steel slag: silica fume is 6:3:1, the modulus of lye is 1.2, the content of lye is 6 %, and the compressive strength of slag-steel slag-silica fume base polymer reaches 2.44 MPa under the standard curing condition of 28 day. The results show that the hydration products of geopolymer mainly consist of calcium-silicate-hydrate (C-S-H) gel and a small amount of ettringite (AFt) crystal. The addition of slag reduces the calcium/silicon ratio and increases the aluminum/silicon ratio, which makes the gel polymerization degree increase. C-S-H gel can be formed by the reaction of calcium hydroxide and silicon dioxide produced by steel slag hydration. Silica fume can provide highly reactive silicon for the system, and its seed effect and pozzolanic effect can accelerate the hydration process of the system.

In response to the problems of small diffusion area, short solidification time, and poor flowability of existing fire extinguishing materials in preventing coal spontaneous combustion in goaf areas of western mining areas, this paper studies a thickened slurry with good flowability and fast diffusion ability. The optimal ratio of thickened slurry was determined through orthogonal experiments, and the rheological properties, impregnation characteristics, and wall hanging characteristics of the material were studied. The results showed that when the water to soil ratio was 8:1, and the concentrations of sodium alginate (SA) and apigenin were 0.6 % and 0.5 %, the flowability and suspension performance of the thickened slurry were the best. When the soaking time is 14 days, the best soaking degree of the material can be achieved, with a soaking depth of 0.93 mm. Through wall hanging tests, it was found that the thickened slurry can naturally air dry on the surface of vertically placed coal pillars with a small sliding distance, which has good adhesion and retention characteristics. Further on -site experiments have shown that by injecting thickened slurry, the CO concentration at the return air corner is significantly reduced, indicating that thickened slurry can cover a large area of residual coal in the goaf, prevent contact between coal and O 2 , and effectively prevent the composite reaction between coal and oxygen.

Vibration frequency and vibration duration are disturbance factors for the structural properties of clay. This study investigates how the vibration frequency and vibration duration from construction disturbances affect the mechanical properties of Zhanjiang Formation structural clay. An electric, frequency-adjustable vibration table applied varying frequencies and durations of vibration to undisturbed soil, creating structural clay samples with different disturbance degrees. Unconfined compressive strength tests and one-dimensional consolidation compression tests were conducted on these samples to obtain disturbance degrees RDq and RDS, defined by strength loss values and compression deformation characteristics, respectively. Orthogonal experiments and grey correlation analysis were used to explore the effects of vibration frequency and vibration duration on the mechanical properties of Zhanjiang Formation structural clay. The results indicated that disturbance degrees RDq and RDS increased linearly with increase in vibration frequency and vibration duration. Range analysis was conducted using two-factor three-level orthogonal experiment of disturbance degrees, and a grey relational analysis model was established to determine the primary and secondary effects of vibration duration and vibration frequency on the mechanical properties of Zhanjiang Formation structural clay. The results demonstrated that the findings from orthogonal experiments and grey relational analysis were consistent, showing that vibration duration had a more significant impact than vibration frequency on the mechanical properties of structural clay. The conclusion suggests that vibration disturbance manifests as a fatigue damage effect. Continuous vibration disturbance progressively weakens the cementation bonds between soil particles due to accumulated energy, leading to gradual fracture and destruction. With constant vibration frequency, longer durations, or with constant duration, higher frequencies intensify the fatigue damage effect of vibration disturbance. Furthermore, during vibration disturbance, Zhanjiang Formation structural clay shows a more pronounced fatigue damage effect from vibration duration than from vibration frequency, with cementation bonds between soil particles weakening more effectively due to accumulated energy. The research findings enhance the understanding of how vibration frequency and vibration duration from disturbance sources impact the mechanical properties of Zhanjiang Formation structural clay, offer theoretical guidance for using construction vibration machinery, and provide a reference for preventing and controlling soil disturbance.