Advanced Materials Research Vols. 261-263

Abstract: A lot of slopes will be formed in the process of engineering construction, and how to ensure the slope stability has become a very key field and common concern to geotechnical engineering. Taking the slope of a open pit mine as an example, the slope stability at original state is analyzed firstly, and then, the optimal control measure and the slope stability trend during the treatment are also researched. The results show that at the original state, the slope stability is worse, and a large contiguous plastic regions will occure on the slope. After comparing to some methods, local unloading is identified as the optimal control measure. When unloading works are carried out and finished, the slope will be in a steady state, and the slope safety factor will up to 1.46, it satisfy engineering requirement.

Abstract: Gypsum breccia is a kind of soft rock-hard soil, and its component is complex. It has poor cementation, low intensity, strong water reaction, slight expansibility and corrosion. During the tunnel construction of gypsum breccia stratum, the mechanical characteristic of supporting structure is very complex. In order to ensure the safety, reasonability and economy of tunnel support system, it is important to acquire the information on displacement and stress of surrounding rock and support system. Two test sections are selected to monitor. Based on the measured data, the distribution characteristics and the time variation law of different kinds of support in gypsum breccia stratum are studied, including surrounding rock pressure, axial force of rock bolt, support pressure and stress. Such conclusions can be got: When strengthened lining (16# I-steel) of the V-grade surrounding rock used, support system performs well; but the stiffness of primary support is not enough if grillage lining is used. Growth of surrounding pressure is for a long time, which shows that the rock mass has Flow characteristics. Especially the surrounding rock pressure increases continuously. The spatial distribution is random, and the value is large. The stiffness of support system should be strengthened. Most blots at the waist arch are compressive. Bolts at the foot arch and sidewall are under tension. The maximum is nearly 124kN. Contact pressure between primary support and secondary lining at the sidewall is higher than that at arch parts. Steel frame stress comes up to 80% of the maximum within 20 days. Excavation of invert has great influences on stress state of surrounding rock and support system.

Abstract: In this paper, concerning the geotechnical properties and erosion circumstances of Jinjiang riverbank of Yangtze River, field on-site investigation and soil laboratory tests were conducted. Study results reveal that the soil of Jinjiang riverbank contains mostly the silt particles with 24% of clay content, the unconfined compressive strength of the soil decreases rapidly and permeability have a significant increase with the small change in water content, which are considered to be primary factors of occurrence of riverbank collapse when flooding occur. In addition, it is cleared that collapse process of riverbank are mainly due to the formation of tension crack and toppling behind the bank face.

Abstract: Google Earth (GE) has powerful functions to view landscapes in fairly realistic three dimensions (3D) as well provides digital elevation model (DEM) data. A GE-based method in terrain surveying of debris flow watershed was elaborated, consisting of DEM data and related functions in GE. The method was employed in 9 debris flow watersheds along Ya-lu Expressway, Sichuan, China. It was proved to be able to get a similar result with traditional map method, especially in the debris flow watershed with a large area, such as more than 12 km². Moreover, the GE method is a time-saving method and can extract some of the terrain parameters directly, which is obviously better than traditional method.

Abstract: With the increase of traffic volume, the enlarging tunnel span and the decreasing of surrounding rock integrity, the level of surrounding rock will be lower. This article proposed the calculating method of relative integrity index based on the concept of relative integrity of surrounding rock and established the Fuzzy Comprehensive Evaluation Method for rock classification by analyzing the impact of tunnel span enlargement upon rock stability. It also specified the determination factors, discussed the selection of weight indexes and proposed methods of establishing the qualitative and quantitative subordinate degrees. Based on practices of the expressways of Fuzhou, Xiamen and Zhangzhou, this article made fuzzy comprehensive evaluation of rock classification and fully analyzed the results of the evaluation. Results showed that with the enlargement of tunnel span, levels of surrounding rock would lower accordingly, and that the worse surrounding rock was, the more it would lower.

Abstract: Based on the Winkler's hypothesis, this paper discusses how to determine the spring constant of groundwork in design of underground structure. When no sufficient experimental conditions are available, the method of numerical calculation can be used to determine the value of spring constant of groundwork. The resulted value is basically the same as the value of experience from the engineering criterion.

Abstract: based on the finite element method of superstructure-the pile raft foundation-the foundation soil action and interaction are studied. Research shows that the common function is considered, fundamental overall settlement and differential settlement with the increase of floor of a nonlinear trend. The influence of superstructure form is bigger for raft stress, the upper structure existing in secondary stress, and the bending moment and axial force than conventional design method slants big; With the increase of the floors, pile load sharing ratio is reduced gradually,but soil load sharing ratio is increased. Along with the increase of the upper structure stiffness, the load focused on corner and side pile; Increasing thickness of raft, can reduce the certain differential settlement and foundation average settlement, thus reducing the upper structure of secondary stress and improving of foundation soil load sharing ratio, at the same time the distribution of counterforce on the pile head is more uneven under raft, thus requiring more uneven from raft stress, considering the piles under raft and the stress of soils to comprehensive determines a reasonable raft thickness, which makes the design safety economy. As the foundation soil modulus of deformation of foundation soil improvement, sharing the upper loads increases, counterforce on the pile head incline to average, raft maximum bending moment decrease gradually.

Abstract: In the construction of shield tunnel, the strength of reinforced soil in the front of departure shaft concerns directly the security of construction. Based on Mechanics of Elastic Structures theory, a thin plate model about reinforced soil is introduced, the maximum stress on reinforced soil is calculated. The security of strength in reinforced area is discussed. With the derived formulas, the needed bending and shear strength of reinforced soil in the project of Beijing Metro Line No. 4 is calculated beforehand, and appropriate material and construction parameters are selected in reinforcement according to the calculate result.

Abstract: The initiation is the core issue in debris flow study, it’s the basis of debris flow disaster prevention, and the research on transformation of landslide into debris flow is fundamental in debris flow study. Transformation of landslide into debris flow was a new topic which proposed in recent years, although it contained the previous areas of landslide-debris flow, something developed, it was more emphasis on the transformation process of landslide to debris flow. This paper proposed an ideal model from practical disaster, based on Coulomb Particle Flow Theory, we used large-scale finite difference software FLAC3D to analyze. From soil mechanics, to study on excess pore water pressure and the instability mechanism of slope, we got several laws. The results showed that, (a) the maximum excess pore water pressure occurred in the lower part of gravel slope body, with the increase of external load increasing, here would be the first liquefaction area; (b) crushed gravel soil had been largely destroyed when the slope in critical state, and at the same time internal energy of particles increased, cement ability decreased. With the rock sheared, gravitation energy of rock was released, high-speed gravel slope spilled into debris.

Abstract: The in-situ tests of horizontal bearing capacity on inclined steel pipe piles were conducted in the sea near Shanghai. Based on the field experiment with the lateral unidirectional and single cycle loading test method, this document presents the horizontal displacement and bearing capacity on the inclined steel pipe piles with negative and positive inclination angles. And the horizontal bearing capacity of the steel pipe pile with positive inclination angle is larger than the one with negative inclination angle. And the tests results can be provided for similar engineering reference.