Advanced Materials Research Vols. 446-449

Abstract: It is difficult for the large diameter pile to bore the hole and ensure its quality under the complicated geological condition in karst areas. In order to get the feasible construction method, the construction technique of super-large diameter rock-socketed piles in karst areas was explored in this paper on the basis of Hezhang Super Maior Bridge project in Guizhou province. The adaptability of the construction plan at this site was expounded firstly; and then the technologies for dealing with the problems of buried hammer, inclined hole, slurry leakage, which often occur during the process of boring pile hole under complicated geological conditions, were deeply researched. The research results show that it is effective to use the slurry with the relative density of 1.30 to 1.35 to prevent the pebble soil layer from collapsing, to prevent the pile hole from inclining by backfilling rubble in tilted stratum, to treat the slurry leakage problem by backfilling rubble, clay soil and bagged cement; and to handle the hammer stuck through the skills of underwater blasting, salvaging with pothook and light pounding with small hammer. It is proved that the method of light pounding with small hammer is preferable to handle the stuck hammer occured in backfill hole. The study provides the theoretical guidance and reference for similar projects.

Abstract: In order to study the stability of layered rock mass, a shear failure criterion for layered rock mass is presented and its program is compiled in C language. The shear failure criterion consists of two parts: firstly, four empirical expressions are suggested in which shear strength parameters vary with the direction; secondly, a pilot calculation method is developed to judge whether a shear failure plane in layered rock mass occurs or not and give its occurrence under three dimensional stress condition. A triaxial numerical experiment on layered rock mass is designed to test the shear failure criterion, and its results reflect the characters including obliquity effect, confining pressure effect and failure mode which conform to the previous triaxial tests.

Abstract: The equipment of large vibration compaction was designed and adopted to simulate the changes of mechanical properties of mixture, by large laboratory vibration compaction test under the condition of different water content and different soil-stone proportion with sandy soil, silt soil and low liquid-limit clay. The deformation capability in each direction of foundation mixture in different compactness was studied by analyzing poisson′s ratio. The change law of poisson′s ratio, shear-wave velocity, longitudinal wave velocity of mixture in different compaction degree were revealed. Model of correlation between poisson′s ratio (μ) and ratio of the S to P wave velocity (ε) was proposed. The model was verified by extra test. The results show that the relationship between μ and ε is not accord with theoretical formula because of special particle shape and distribution of the soil-stone mixture. The change regularity of mixture poisson′s ratio in different conditions can be reflected well by the model. The new method of field test of poisson′s ratio in soil-stone foundation with ratio of the S to P wave velocity is proposed. The conclusion is valuable in poisson′s ratio study of soil-stone mixture.

Abstract: Abstract—The article describes the growth and thermal resistance characteristics of the debris formation of the urban sewage source heat pump system, and describes the common measures.

Abstract: In order to study the safety situation in each part of rock mass, the element safety factor Fe is introduced to estimate the micro-stability of rock mass; the equation for the element safety factor is deduced by the theoretical analysis. Rather than base an engineering design decision on a single calculated factor of safety, an approach which is frequently used to give a more rational assessment of the risks associated with a particular design is to carry out a sensitivity study. This involves a series of calculations in which each significant parameter is varied systematically over its maximum credible range in order to determine its influence upon the factor of safety. In the present paper, the element safety factor Fe is introduced to estimate the micro-stability of rock mass; the equation for the element safety factor is deduced by the theoretical analysis, and the influential factors to the element safety factor is studied.

Abstract: Based on the consolidated undrained triaxial test of soft clay, a formula for computing pore water pressure is developed, by using of the critical state theory of volume strain and the characteristic normalization of soft clay. It is shown that the new proposed formula is reasonable to reveal the nonlinear stress-strain relationship and the dilatancy characteristics of soft clay. With the comparison between the pore water pressure simulation results by the new formula and the experimental data, it is shown that the simulation values agree well with the experimental data. Meanwhile, based on the failure criterion, a formula for the critical pore water pressure is proposed. It is shown that the new formula is reasonable to simulate the critical pore water pressure. It is very useful to predict the foundation stability.

Abstract: Abstract: Cast-in situ bored pile is a common form of pile foundation and widely used in road and bridge engineering in China. Because of complex cast-in situ bored pile construction process, high technical content requirement, vulnerable to the impact of human and environmental factors, cast-in situ bored piles prone to various kinds of quality problems in the construction process, such as drilling deflection, drilling hole collapse and diameter reduction, wrong identification of pile-end’s bearing stratum, catheter tube blockage, reinforcement cage floating, pile breaking, pile silted, etc. These problems often make it difficult to meet the design requirements into a pile formation, and difficultly to remedy. In this paper, Zhoutian Zhenjiang bridge at Shaoguan City, Qujiang to Nanxiong highway A03 contract bid package cast-in situ bored pile foundation engineering encountered in the construction collapsed hole, inclined hole, catheter tube blockage and other issues for example to analyzes the cause of cast-in situ bored pile engineering accident, made appropriate preventive measures and processing method.

Abstract: For the long elastic pile, the “m” method is often used to solve the elastic deflection differential equation, and the bending rigidity of pile can be obtained. The single pile can be replaced by one column fixed at two ends which has the same rigidity of the pile to solve the interaction problem of pile, base beam, and upper structure. So the influences of the pile construction error on base beam can be calculated. The analysis example shows that compared with no construction error of pile, the bending moment and the reinforcement of base beam increase greatly in the scope of allowable maximal construction error stipulated by the Code. The calculation method of the internal forces of base beam is put forward.

Abstract: In order to implement the non-linear Hoek-Brown (HB) shear strength reduction (SSR) on commercially available softwares, this paper derives the relationship between the Drucker-prager (DP) criterion and HB criterion under the condition of plane strain. The equivalent DP parameters can be approximately estimated after serious transformations of parameters between the HB and Mohr-Coulomb (MC) yield functions. To assess the effect of dilation on the stability of slope, the non-associated flow rule, which cannot be contained in the existing limit equilibrium methods, is selected in our analysis, and the SSR-based results of a simple slope indicate that: If the angle of dilatancy ψ is taken to be zero, the factor of safety calculated by the SSR method is very close to that by the limit equilibrium method; if ψ is greater than zero, the factor of safety calculated by the SSR method is greater than that by the limit equilibrium method, and the effect of dilation on the stability of slope can be approximately described by a liner function.

Abstract: The quality of pre-investigation and other reasons would lead to the disagreement between the depth of prefabricated vertical drain(PVD) and actual soft ground foundation. All these factors would have a seriously bad effect on the subsidence and the stability of soft ground foundation. The author combines the Suining-Ziyang-Meishan expressway project, detailedly analyses the correlation between different depths of PVD and actual soft ground foundation based on observation settlement data. The results shows: Before the limit fill height(LFH), with load increases, the depth of PVD has little effect on subsidence rate, the curve of PVD depth-subsidence rate is approximately linear; when backfilling height exceeds the LFH, the closer depth of PVD is to actual depth, the more obvious soft foundation reinforcement effect is, the larger rate and value of subsidence are. However, when PVD depth is 1m deeper than the actual, subsidence rate decreases. In addition, according to the difference of observation total settlement and theoretical calculation settlement due to the difference between PVD depth and actual, adjust preloading period to meet the requirements of pavement construction and post-construction settlement.