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Ground volume loss is an important parameter for settlement control and prediction in shield tunneling. This parameter is usually determined empirically, while its variation along the tunnel is not predictable. In this study, an analytical formula for ground volume loss is obtained based on physical derivation. The ground volume loss is divided into two components. Key operational parameters, i.e. face pressure, grouting pressure and grouting volume, are used to calculate the two components. The proposed formula is then validated against the field data collected from Changzhou Metro in thick silty clay layer. The validation shows that the new formula gives reasonable prediction of ground volume loss. Furthermore, the three model coefficients derived from physical calculation are very close to the regression coefficients based on statistical method. For EPB tunnels excavated in silty clay layer, the ground volume loss along a specific tunnel can be predicted by the new formula. The analysis also indicates that the surface settlement of EPB tunnel should be controlled by a balanced combination of varied operational parameters.

The rapid progress of urbanization and industrialization has led to the accumulation of large amounts of metal ions in the environment. These metal ions are adsorbed onto the negatively charged surfaces of clay particles, altering the total surface charge, double-layer thickness, and chemical bonds between the particles, which in turn affects the interactions between them. This causes changes in the microstructure, such as particle rearrangement and pore morphology adjustments, ultimately altering the mechanical behavior of the soil and reducing its stability. This study explores the effects of four common metal ions, including monovalent alkali metal ions (Na+, K+) and divalent heavy metal ions (Pb2+, Zn2+), with a focus on how ion valence and concentration impact the soil’s microstructure and mechanical properties. Microstructural tests show that metal ion incorporation reduces particle size, increases clay content, and transforms the structure from layered to honeycomb-like. Small pores decrease while large pores dominate, reducing the specific surface area and pore volume, while the average pore size increases. Although cation exchange capacity decreases, cation adsorption density per unit surface area increases. Monovalent ions primarily disperse the soil structure, while divalent ions induce coagulation. Macro-mechanical tests reveal that metal ion contamination reduces porosity under loading, with compressibility rises as the ion concentration increases. Soils contaminated with alkali metal ions shows higher compression coefficients at all loads, while heavy metal ions cause higher compression under lower loads. Shear strength, the internal friction angle, and cohesion in metal-ion-contaminated clay decrease compared to uncontaminated field-state clay, with greater declines at higher ion concentrations. The Micropore Morphology Index and hydro-pore structural parameter effectively characterize both micro- and macrostructural properties, establishing a quantitative relationship between HPSP and the engineering properties of metal-ion-contaminated clay.

Earth pressure for saturated cohesive soils is closely related to the effective stress expression. For cohesionless soils, previous research indicated that the fraction of pore pressure (factor η) in the effective stress expression is below unity at high pressures. However, for cohesive soils, reliable η-value has not been reported. In this study, experimental data from direct shear and triaxial tests were analyzed in order to derive the η-values of two cohesive soils. It was shown that η-value of cohesive soils decreases significantly with increasing effective stress, and the values of η derived from different experiments were consistent with each other. The obtained values of η were applied to the calculations of lateral earth pressure. The lateral earth pressure based on real η was compared with the results of traditional methods, i.e., effective stress analysis (ESA) and total stress analysis (TSA). The traditional ESA was conservative because of the overestimation of active earth pressure. Such conservatism was more significant for high plasticity clay. Contrastingly, TSA results were risky for both of the two cohesive soils.

Objective To explore the effect and feasibility of using two pumps linked automatic equipment to collect autologous blood of acute normovolemic hemodilution (ANH) in improving blood collection speed, accurately controlling the proportion of normovolemic hemodilution and stabilizing the hemodynamics of laboratory animals. Methods Sixteen Bama miniature pigs were monitored and recorded of heart rate and blood pressure as laboratory animal model underwent ANH autologous blood collection with both the methods of manual mode and automatic equipment mode. The blood collection speed, total amount of hemodilution solution and accuracy of normovolemic proportion control of the two methods were compared. The changes of hemodynamic parameters before and after ANH blood collection were observed and compared between the two methods. Results In the manual group, the blood collection speed was (10-26.7) g/min, with an average of (16.0±5.6) g/min, and the amount of hemodilution solution was (260-550) g, with an average of (385.4±76.2) g; in the automatic equipment group, the average blood collection speed was (40.4±0.6) g/min, which was significantly faster(P

The Pulse-Pre-Pump Brillouin Optical Time Domain Analysis (PPP-BOTDA) based distributed fiber optic sensing (DFOS) technique has a unique advantage of achieving full-distributed structural strain with cm-order spatial resolution, which is ideal for fine stress monitoring of the pile foundation. The high spatial resolution helped to detect local changes and defects while inevitably led to noisy data meanwhile, especially a certain part of anomalous sensing data. Therefore, a robust algorithm of random sampling consistency (RANSAC) was employed to extract and process the DFOS data. In a field static load test, the variation of strain along a precast pile was measured with PPP-BOTDA interrogator. The axial force and frictional resistance were calculated based on the RANSAC processed strain data. The pile-soil interface properties were estimated as well. It shows the feasibility and good performance of PPP-BOTDA in the measurement of precast piles stress test. The RANSAC proves to be an effective method for processing DFOS data with a certain number of outliers. This work presents a valuable reference for DFOS based pile stress test and data analysis which will promote its application in other related structural health monitoring purpose.

Taking into account the effects of lattice vibrations and surface electrical field on carrier mobility, a unified formalism is developed to calculate the electrical parameters of silicon W-MOSFETs. These parameters, including conductance and saturation drain current, are measured at varying temperatures and under strong surface fields. The experimental results deviate from the values estimated with the previous theories, but they are in good agreement with our calculations. [ABSTRACT FROM AUTHOR]