Advanced Materials Research Vols. 378-379

Abstract: Considering the erosion effect of underground water deteriorate the micro structure of rock which results in the time effect of rock deform, the paper developed a uniaxial compression equipment for rock creep under chemical and stress coupling action. It adopts good corrosion prevention design, can conveniently test the rock uniaxial compression creep effect with erosion. Take limestone as study object, the paper carried out uniaxial compression creep tests with different PH environment. Compared the results of different tests and found that limestone has obvious creep effect in acid solution, the smaller the PH value is, the greater the creep deform is. For the same test specimen, the creep deform of primary stage is larger than that of later stage. In each level load, the creep velocity decreases along with the time increasing. Analyzed result shows that the equipment has provided basement for studying the rock creep mechanism with chemistry and stress interaction.

Abstract: In order to study the effect of mining excavation on planed structure on ground surface, the effect of certain mining excavation on ground stabtility was calculated by use of the advanced Ansys FEM computation program. The recults can not only provide ground deformation parameters for planned structure, but also give light for understanding the deformation mechanism of mining excavation.

Abstract: With the development and utilization of underground space, some new tunnel forms are emerging, such as the rectangular tunnel, double tunnels, treble tunnels and so on. The aim of this paper is to determine the collapse face pressure of a rectangular tunnel driven by a pressurized shield. The calculation is based on the upper-bound method of the limit analysis theory. A translational kinematically admissible failure mechanism consists a sequence of truncated rigid cones are considered for the calculation schemes. The numerical results obtained by the calculation are presented.

Abstract: This study focuses on the method to determine the slip surface in waterfront soil slope analysis under static and seismic conditions. Based on the limiting equilibrium theory and the stress analyzing method, a new method to determine the slip surface is suggested. In the method, the two basic assumptions are considered in order to solve the problem. One is that the slip surface comprises a series of straight lines, and the other is that the interslice boundary is an inclined plane. Three balance equations for any slice are proposed. The iterative method to solve the balance equations is also suggested. In the new method, the slip surface is obtained slice by slice going from downhill to uphill in terms of the balance equations of the slice, not predefined.

Abstract: Based on the treatment of in-situ foundation, two distinct model tests for pile-net composite foundation in super large area and deep soft soil with different pile spacing were designed to study the bearing behavior of the piles. The result shows: the axial force of pile shaft increases with the growth of embankment filling load and gradually rises down along pile shaft to a certain depth, then slowly decreases afterwards. The velocity of force changing varies from the correlated soil layers, which indicates that pile shaft resistance appears to be unlike in different pile sites; The ratio of pile shaft resistance area to the overall pile length is relatively high while of normal resistance area is smaller ,and when the upper load is mainly supported by bearing course on pile end, pile-net composite foundation turns to be friction and end-bearing pile; For each level of loads, both pile-soil stress ratio and load shearing ratio of pile increase modestly, then tend to be steady till the next load level is applying on.

Abstract: Considering the dynamic nonlinear characteristics of soil by equivalent linear method, one-dimensional wave models were established to study the seismic effects along depth of deep soft sites under far-field ground motions of great earthquake. The results show that the magnified effect of acceleration response spectrum of each layer present more outstanding under far-field ground motions than under Suzhou artificial waves, with the increasing of bedrock peak ground acceleration, there is probability that the peak of long-period component of acceleration response spectrum appears higher than that of the short-period within 15m depth, which may adversely affect the long-period building structures. However, the reduction coefficient of peak ground acceleration (PGA) along depth according to the three levels of earthquake fortification standard was relatively higher when inputting far-field ground motions of great earthquake. As the curve fitted by Longjun Xu et al. based on records collected California Strong Motion Instrumentation Program geotechnical arrays of the United States and Hosokura Mine arrays of Japan, is not suitable for Suzhou area, suited quantitative formula about reduction coefficient curve of PGA with depth in deep soft site is given. Besides, maximum shear strain at the depth of approximately 15m and 40m present to be greatly changed when inputting far-field ground motions of great earthquake, with the growth of inputting bedrock peak ground acceleration, the layer in the depth of about 15m comes to be the most unfavorable position of shear deformation.

Abstract: The tunnel construction often encounters the problem of adaptability of sand-gravel formation and earth pressure balance shield (EPBS) construction, which has brought new technical problems and challenges to those who are participating in the construction project. In order to ensure the normal operation of shield construction, the soil must have ideal plasticity and liquidity, and low permeability to intercept groundwater. Therefore, we must adopt the soil improvement techniques ,namely, to inject the modified materials (mud, foam, polymer, etc.) into excavation face and earth pressure tank(if necessary, to the screw conveyor) to ensure the stability of excavation face, achieve EPBS driving, and help to reduce mechanical load, reduce land subsidence, and increase driving speed at the same time. The ground improvement technique is an important part of the EPBS method. The quality of the application of soil improvement technology is very important to maintain the stability of excavation face and the screw dump device’s dumping smoothly. It also has a significant impact on the shield machine’s functioning safely,economically and efficiently.

Abstract: Landslides induced by many reasons had resulted in heavy casualties and property losses. Therefore, the research on the failure process of the slope and its final accumulation state is necessary. In this paper, three-dimensional particle flow model is established in PFC3D to simulate the slope failure process, triggered by gravity and seismic load respectively, and the final accumulation state. The landslide movement passing valleys of different shapes are studied and compared. The results show that the shape of valley section has great influence for both load cases.

Abstract: Considering the typical semi-rigid pavement structure, combined with our existing asphalt pavement structural design specification indicators and pavement analysis evaluation indexes, this paper discussed the changing of surface deflection and the tensile stress of the bottom of asphalt pavement graded aggregate base on load axle center under subgrade transversely isotropic, different speeds and non-uniform dynamic load ,when the vehicles running to the central road of model which has a good guide for low speed controlling and service life extension of the road.

Abstract: The blasting vibration derived from multiple blasts and its effects on surrounding rock in a longspan tunnel will probably give rise to cumulative damage of surrounding rock, and weaken surrounding rock’s stability. Blastmate III, made by the Canadian company Instantel, is utilized to monitor the vibration signals from multiple blasts. Blasting vibration decay law and allowed safety distance of blasting are calculated by using Sadaovsk formula. Then, cumulative effects are analyzed by Hilbert-Huang Transform method as well as consequential instantaneous energy spectrum, and UTEP is presented to indicate the change of cumulative effects and damage in surrouding rock. The research shows that during the progress of damage evolution, “strengthening” and” deteriorating” may alternately appear several times. This is a zigzag reciprocating process in damage evolution of surrounding rock.