A local homogenization approach for simulating the reinforcement effect of the fully grouted bolt in deep underground openings

Fully grouted bolts are a key component of the support system for underground openings.Although considerable effort has been made in the simulation of the reinforcement effect of the fully grouted bolts on the rock masses surrounding underground openings,most of the work has limited significance since the structural element approach is used.This study proposes a local homogenization approach(L-H approach)that integrates elastoplastic mechanics,composite mechanics,and analytical approaches with numerical simulation to effectively simulate the reinforcement effect of the fully grouted bolt on deep surrounding rock masses.In the L-H approach,the representative volume of bolted rock mass(RVBRM)with a fully grouted bolt is established based on the original mesh model utilized in the rockbolt element approach.The RVBRM is a regular quadrangular prism with a cross-sectional size equal to the bolt spacing and a length equal to the bolt length.The RVBRM is homogenized by the L-H approach from a unidirectional bolt-reinforced composite into a homogeneous transversely isotropic medium whose mechanical properties are described by a new transversely isotropic elastoplastic model.The L-H parameters for the RVBRM are obtained using analytical approaches,composite mechanics,and known parameters of the rock mass and bolt.Using the L-H approach,the reinforcement effect of the fully grouted bolt on the bolted rock specimen and the surrounding rock mass in Jinping II Diversion Tunnel#2 with a depth greater than 2000 m is simulated.The results show that the predictions of the L-H approach are more in agreement with the physical model results of bolted rock specimen and provide a more realistic response of the bolted surrounding rock mass.The L-H approach demonstrates that fully grouted bolts with common bolt spacings and diameters substantially enhance the elastic modulus,shear strength,and tensile strength of the rock mass in the direction of the bolt axis.

Investigation of reinforcement of the modified carbon black from wasted tires by nuclear magnetic resonance

Pyrolysis has the potential of transforming waste into recyclable products. Pyrolytic carbon black (PCB) is one of the most important products from the pyrolysis of used tires. Techniques for surface modifications of PCB have been developed. One of the most significant applications for modified PCB is to reinforce the rubber matrix to obtain high added values. The transverse relaxation and the chain dynamics of vulcanized rubber networks with PCB and modified PCB were studied and compared with those of the commercial carbon blacks using selective 1H transverse relaxation (T2) experiments and dipolar correlation effect (DCE) experiments on the stimulated echo. Demineralization and coupling agent modification not only intensified the interactions between the modified PCB and the neighboring polyisoprene chains, but also increased the chemical cross-link density of the vulcanized rubber with modified PCB. The mechanical testing of the rubbers with different kinds of carbon blacks showed that the maximum strain of the rubber with modified PCB was improved greatly. The mechanical testing results confirmed the conclusion obtained by nuclear magnetic resonance (NMR). PCB modified by the demineralization and NDZ-105 titanate coupling agent could be used to replace the commercial semi-reinforcing carbon black.

Reinforcement effects of ground treatment with dynamic compaction replacement in cold and saline soil regions

The mechanical property of saline soils varies with moisture and climate in the cold and salt lake region of Qinghai-Tibet Plateau, which influences project construction. In order to improve foundation reinforcement effect of the QarharvaTrolmud Highway, Qinghai Province, China, dynamic compaction replacement （DCR） composite foundation was applied in saline soils. A field experiment was conducted in this area, where strength and working mechanism of pier-soil and deformation modulus of the composite foundation was analyzed after reinforcement. This paper presents methods for determining the coefficient on the bearing capacity evaluation and deformation modulus of composite foundation with DC1L Reinforcement case of DCR is highly effective in saline soils of the salt lake regions, which helps the mi-tion of water and salt in saline soils.

Reinforcement of Clay Soils through Fracture Grouting

Fracture grouting is widely used for building foundation reinforcement,however the underpinning mechanisms are still not clear.Using numerical results about a single-hole fracture grouting process as a basis,a model composed of soil and grouting veins has been created to analyze the reinforcement mechanism.The influence weights of the grouting vein skeleton and compaction effect have been studied,thereby obtaining relevant information on the compressive modulus of the considered composite soil.The research results show that the compaction effect plays a leading role in the soil fracture grouting reinforcement.The grouting pressure,the hardened grouting vein modulus,and the shape of the grouting veins all influence the compressive modulus of the composite soil.

Vacuum preloading combined electroosmotic strengthening of ultra-soft soil

To assess the effectiveness of vacuum preloading combined electroosmotic strengthening of ultra-soft soil and study the mechanism of the process, a comprehensive experimental investigation was performed. A laboratory test cell was designed and applied to evaluate the vacuum preloading combined electroosmosis. Several factors were taken into consideration, including the directions of the electroosmotic current and water induced by vacuum preloading and the replenishment of groundwater from the surrounding area. The results indicate that electroosmosis together with vacuum preloading improve the soil strength greatly, with an increase of approximately 60%, and reduce the water content of the soil on the basis of consolidation of vacuum preloading, howeve~ further settlement is not obvious with only 1.7 mm. The reinforcement effect of vacuum preloading combined electroosmosis is better than that of electroosmosis after vacuum preloading. Elemental analysis using X-ray fluorescence proves that the soil strengthening during electroosmotic period in this work is mainly caused by electroosmosis-induced electrochemical reactions, the concentrations of Al2O3 in the VPCEO region increase by 2.2%, 1.5%, and 0.9% at the anode, the midpoint between the electrodes, and the cathode, respectively.

Application of dynamic compaction and rolling compaction in the subgrade improvement of Qarhan-Golmud Highway

Melt shrinkage, salt bulge, and corrosiveness are common problems with saline soils, which damage highway foundations and cause huge financial losses. In order to improve the saline soil subgrade, dynamic compaction （DC） and rolling compaction （RC） technology were applied on the Qarhan-Golmud Highway in Qinghai Province, China. A field experi- ment was conducted in which shear strength, deformation modulus, and the working mechanism of the composite foun- dation were analyzed after reinforcement. Both the DC and RC methods were found to be effective and helped to improve the foundation strength of saline soils, although the ultimate bearing capacity and deformation modulus of the RC method were lower than that of the DC method.

SEM in-situ Fracture Observation and the Reinforcing Effect of Composite SiC_p/ZA22

The strengthening effect of a Zn alloy reinforced by SiC particulate was examined. Based on the results of SEM in-situ fracture observation and stress field analysis by finite element method, it is believed that the reinforcing effect of this composite is due to the combination of strain and stress hardening in the matrix.

Fabrication and characterization of in situ AlN–TiN/Al composite ribbons

The conventional wisdom is that the distribution and sizes of reinforcements, as well as the bonding strength of the matrix–reinforcement interface tend to be the crucial factors in determining the resulting properties of composites: the optimum mechanical properties are likely to be achieved when fine and thermally stable reinforcing particles are homogeneously distributed in a metal matrix.In this study, in situ AlN–TiN/Al composite ribbons were successfully synthesized through plasma jet and subsequent melt-spinning method. The distribution and sizes of the particles in the ribbon were systematically investigated.The average grain sizes of AlN and TiN in the AlN–TiN/Al composite ribbon are determined to be 27.7 and 29.6 nm,respectively. Moreover, analysis by scanning electron microscopy(SEM) results reveal that, compared with the AlN–TiN/Al bulk composite, particles like AlN and TiN could be far more homogeneously distributed in the matrix of the ribbon counterpart. In addition, the reinforcing effect of in situ nanoparticles, including AlN and TiN, was discussed as well.

Effect of Reinforcing Qi and Moistening Intestine Oral Liquid on Anorectal Manometry of Asthenia Type Constipation Patients

Objective: To study the change of anorectal manometry in asthenia type constipation patients and effect of reinforcing Qi and moistening intestine oral liquid (RQMI) on it. Methods: The total of 135 cases were divided into healthy group, RQMI treated group, Maren pill (MRP) treated group and prepulsid (PPS) treated group, their anal maximal voluntary squeez pressure, rectoanal contraction reflex, rectoanal inhibitory reflex, defecation reflex, rectal volume sensory threshold and rectal maximal tolerable volume were observed. Results: The rectal sensory function of patients weakened obviously and anal sphincter reactivity reduced as compared with those of healthy person (P＜0.01), and both were improved by RQMI treatment (P＜0.05). Conclusion: RQMI is superior to MRP and prepulside in improving anorectal dynamic abnormality in constipation patient of asthenia type.