•Polymer grouting trenchless repairing technique of drainage pipe is proposed.•Mechanical behaviour of drainage pipe repaired by polymer grouting is investigated.•The repaired effect of polymer ...grouting pipe is better than the concrete grouting.
Polymer grouting technology is an economical and efficient trenchless way to repair leakage and settlement of drainage pipeline. In this paper, the mechanical behaviours of drainage pipeline under traffic load before and after polymer grouting and cement grouting trenchless repairing are investigated through three-dimensional (3D) finite element method (FEM). Four different working conditions, including normal pipeline, disengaging pipeline, polymer-repaired pipeline, and cement-repaired pipeline are considered. The effects of load type, load location, buried depth on the mechanics of pipe are discussed in detail. The results show that the traffic load has great impact on both sides of the load position within 4 m, and the dangerous points of the pipeline are located at the bell and spigot joints. The most unfavorable condition occurs when the location of the disengaging corresponding to the load position. The greater influence on the disengaging pipeline with deeper buried depth applied. The disengaging pipeline can be repairing effectively and reliably by both the polymer and the cement grouting technology. However, the polymer material is more valuable than the cement material in terms of the Mises stresses after repairing.
The Yellow River silt can be effectively used as highway subgrade filler, which cannot only relieve the flood control pressure in the lower reaches of the Yellow River, but also meet the economic ...development needs of the areas along the Yellow River, with significant economic and social benefits. It cannot be ignored that the highway subgrade may be produced liquefaction under the action of earthquake and traffic loads. The problem of the dynamic characteristics of the Yellow River silt is a fundamental scientific problem that needs to be solved urgently. In this paper, a series of undrained tests were carried out on saturated Yellow River silt. Effects of relative density Dr, effective confining pressure σ3c, loading frequency f and cycles stress ratio CSR on pore pressure, axial strain development characteristics and dynamic strength characteristics of saturated Yellow River silt were studied. The test results show that: The number of cycles vibration required for liquefaction failure of the Yellow River silt was affected by relative density, loading frequency, effective confining pressure and cycles stress ratio. There are significant differences in the stress-strain development patterns of the Yellow River silt under different frequencies. Under the action of low frequency load, the Yellow River silt presents “hardening” liquefaction characteristics. Under the action of high frequency load, the Yellow River silt presents the characteristics of “softening” liquefaction. The Yellow River silt doesn't liquefy under the effect of weak earthquakes, while it is highly susceptible to liquefaction under the effect of strong earthquakes. Compared with the high-frequency load, when the low-frequency load is applied, more energy is required for the Yellow River silt to reach the initial liquefaction state. The cycles stress ratio CSR and the relative density Dr have significant effects on the pore pressure development of the Yellow River silt. Finally, a modified Seed model was proposed to characterize the pore pressure development of the Yellow River silt.
•The liquefaction characteristics of Yellow river silt subgrade filler are investigated.•The effects of confining pressure, relative density and loading frequency were discussed.•The predicted pore pressure model with considering different parameters were proposed.
It is important to be fully aware of the dynamic characteristics of saturated soft clays under complex loading conditions in practice. In this paper, a series of undrained tests for soft clay ...consolidated with different initial major principal stress direction
ξ
were conducted by a hollow cylinder apparatus (HCA). The clay samples were subjected to pure principal stress rotation as the magnitudes of the mean total stress
p
, intermediate principal stress coefficient
b
, and deviator stress
q
were all maintained constant. The influences of intermediate principal stress coefficient and initial major principal stress direction on the variation of strain components, generation of pore water pressure, cyclic degradation and non-coaxiality were investigated. The experimental observations indicated that the strain components of specimen were affected by both intermediate principal stress coefficient and initial major principal stress direction. The generation of the pore water pressure was significantly influenced by intermediate principal stress coefficient. However, the generation of pore water pressure was merely influenced by initial major principal stress direction when
b
= 0.5. It was also noted that the torsional stress–strain relationships were affected by the number of cycles, and the effect of intermediate principal stress coefficient and initial major principal stress direction on the torsional stress–strain loops were also significant. Stiffness degradation occur under pure principal stress rotation. Anisotropic behavior resulting from the process of inclined consolidation have considerable effects on the strain components and non-coaxial behavior of soft clay.
The reinforcement and durability of loess are of great importance for road performance. In this study, a self-designed grouting system and newly permeable polymers were adopted to investigate the ...mechanical properties and durability of solidified loess (SL), considering different dry densities and water contents. The unconfined compression test and piezocone penetration (CPTU) test were used to examine the mechanical properties. The mechanism of the loess solidified by permeable polymer was analyzed from the micro-level by SEM, MIP, and XRD tests. The test results show that the effect of polymer grouting is obvious, the unconfined compressive strength (UCS) of the SL after grouting is as high as 3.05−5.42 MPa; it is 11.83−20.99 times that of unsolidified loess (UL). The UCS of the SL after grouting is inversely proportional to the dry densities and water contents. After 56 days of immersion, the SL still shows a high compressive strength. The additional erosion of the SL was not caused by the salt solution; the durability is significantly better than that of cement mixing soil. The sensitivity of various factors on the UCS of the SL are service environment > water content > dry density. The SEM tests clearly show that the gel formed by the reaction of the polymer with water on the surface of soil particles makes the bond of soil particles tighter. It can be observed from the MIP test that the cumulative mercury of SL was 0.115 mL/g, which was 33.72% of UL (0.341 mL/g), and the cumulative mercury of SL after immersion in water and salt solutions was 0.183 mL/g and 0.175 mL/g, which was 53.7% and 51.3% of UL (0.341 mL/g), respectively. The XRD results show that there are no other new mineral components produced after grouting and the spacing between crystalline planes decreases, which proves that permeable polymer grouting makes the soil denser and does not erode the soil particles.
Cancer immunotherapy has developed rapidly in recent years and stands as one of the most promising techniques for combating cancer. To develop and optimize cancer immunotherapy, it is crucial to ...comprehend the interactions between immune cells and tumor cells in the tumor microenvironment (TME). The TME is complex, with the distribution and function of immune cells undergoing dynamic changes. There are several research techniques to study the TME, and intravital imaging emerges as a powerful tool for capturing the spatiotemporal dynamics, especially the movement behavior and the immune function of various immune cells in real physiological state. Intravital imaging has several advantages, such as high spatio-temporal resolution, multicolor, dynamic and 4D detection, making it an invaluable tool for visualizing the dynamic processes in the TME. This review summarizes the workflow for intravital imaging technology, multi-color labeling methods, optical imaging windows, methods of imaging data analysis and the latest research in visualizing the spatio-temporal dynamics and function of immune cells in the TME. It is essential to investigate the role played by immune cells in the tumor immune response through intravital imaging. The review deepens our understanding of the unique contribution of intravital imaging to improve the efficiency of cancer immunotherapy.
Background:
The outbreak of novel coronavirus disease 2019 (COVID-19) started in the city of Wuhan, China, with a period of rapid initial spread. Transmission on a regional and then national scale ...was promoted by intense travel during the holiday period of the Chinese New Year. We studied the variation in transmission of COVID-19, locally in Wuhan, as well as on a larger spatial scale, among different cities and even among provinces in mainland China.
Methods:
In addition to reported numbers of new cases, we have been able to assemble detailed contact data for some of the initial clusters of COVID-19. This enabled estimation of the serial interval for clinical cases, as well as reproduction numbers for small and large regions.
Findings:
We estimated the average serial interval was 4.8 days. For early transmission in Wuhan, any infectious case produced as many as four new cases, transmission outside Wuhan was less intense, with reproduction numbers below two. During the rapid growth phase of the outbreak the region of Wuhan city acted as a hot spot, generating new cases upon contact, while locally, in other provinces, transmission was low.
Interpretation:
COVID-19 is capable of spreading very rapidly. The sizes of outbreak in provinces of mainland China mainly depended on the numbers of cases imported from Wuhan as the local reproduction numbers were low. The COVID-19 epidemic should be controllable with appropriate interventions (suspension of public transportation, cancellation of mass gatherings, implementation of surveillance and testing, and promotion of personal hygiene and face mask use).
The structural stability of the underwater shield tunnel during operations is affected by temperature variations. The effect of different structure temperatures on the underwater shield tunnel during ...the operation period was studied. By numerical simulation, the variation in the underwater shield tunnel temperature circle was analyzed. The variation patterns of the top arch, bottom arch, waist arch temperature, maximum principal stress, and settlement of the soil under different temperatures were obtained. The results showed that: (1) The early excavation time of the tunnel was short, and the temperature circle was small. The temperature circle expanded rapidly after 50 days of operating. The diffusion range increased from 1.5 m to 5.35 m: an increase of 256.7%. With the increase in time, the expansion rate of the temperature circle gradually slowed down. (2) The higher the temperature of the soil, the more complex the temperature transfer between the soil and the lining was while generating greater temperature stresses and reducing the safety of the tunnel. (3) When the tunnel was just excavated, the compression settlement of the top arch and the waist arch increased rapidly, reaching 5.43 mm and 0.24 mm, respectively. The bottom arch was squeezed by the soil on both sides, resulting in an uplift and rapid increase, reaching 4.94 mm. The settlement rate increased with the increase in the tunnel structure’s temperature. After the excavation, with the decrease in temperature, the strength of the soil and lining increased. The settlement of the top arch, bottom arch, and waist arch increased slowly with time, and the growth rate decreased gradually.
The grinding reinforcement of fine sand layers is a difficult problem in dam engineering construction. As a new type of grouting material, permeable polymer with excellent impermeability and high ...strength is widely used in dam engineering. In this paper, a series of compressive tests were designed considering different grouting pressures, curing days, moisture content, and porosity of fine sand. The influence of grouting parameters and sand layer conditions on the strength of fine sand layers reinforced by permeable polymers was analyzed. SEM and XDR tests were conducted to analyze the microscopic characteristics of the grouting stone. The functional calculation model of the strength and the influencing factors was established to explore the main factors influencing grouting stones. The compressive strength of grouted stones increases rapidly from the 7th to the 14th day, reaching about 96% of the maximum strength. The degree of influence of different factors is grouting pressure > moisture content > porosity. The compressive strength of the grouted stones increases with the increase of grouting pressure and the number of curing days. The compressive strength decreases with the sand layer’s increasing moisture content and porosity.
AbstractDrained torsional shear tests were performed on hollow cylindrical intact soft clay specimens to investigate the anisotropic deformation, strength, and noncoaxial behavior in general stress ...states involving variations in both the magnitude and direction of the principal stresses. Tests were conducted by maintaining a fixed principal stress direction α relative to the vertical direction while keeping the intermediate principal stress coefficient b constant. It was found that the magnitudes of the radial strain εr were dependent on the b value, and the magnitudes of circumferential strain εθ were dependent on the α angle. The influence of b and α on the relationship between volumetric strain and shear stress was less significant. The stress paths for all α angles at b = 0.5 were determined under various stress levels. Furthermore, the experimental results showed that the noncoincidence between the directions of strain increment and stress existed in clay, and the noncoaxiality was influenced by both intermediate principal stress and principal stress direction.
This paper focuses on the shear and dilatancy behavior of wheat stored in silos with various densities and normal stresses. The goal is to find a quantitative relationship modeling the peak friction ...angle and maximum dilatancy angle of wheat stored in silos. A total of 48 direct shear tests were carried out to research the evolution of shear and dilatancy of stored wheat in silos. It is revealed that strength of wheat in bulk attributes to the combination of frictional and dilatant during shearing, in particular attributing to its elliptic shape. An increase in relative density enhances the peak friction angle as well as the dilation. The relationships between relative density, peak friction angle, and dilatancy angle were presented based on the tests data and Bolton’s theory. Then an advanced model is developed to evaluate the peak shear behavior of wheat stored in silos considering the dilatancy of the stored wheat. It is a practical method to predict the strength and dilatancy behavior of wheat stored in silos.
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