Advanced Materials Research Vols. 261-263

Abstract: It’s very common that there are cavities after the lining and seriously affects the health of the tunnels. According to the status that the health standard is not uniform at present, the health levels can be divided into four parts: health, sub-health, disease and sick into death. For studying the single index criterion of lining cavities, and introducing lab large-scale model test combining the engineering example, analyzing the variety of structure bearing capacity, disease producing shapes and varying rule and so on where are different dimension cavities after lining. The results show that the carrying capacity curve expresses reverse S characteristic, it can be divided into slow, fast and complete degradation basis on the variety of velocity, and it is uniform to the sub-health, disease and sick into death, finding out the single health criterion of cavity: it is health where no cavities after the lining, it’s sub-health when the dimension is less than 100mm, disease when the dimension is between 100mm and 550mm, it’s sick to death if the dimension were more than 550mm.

Abstract: This paper puts attention on the application of Chebyshev complex polynomials in the development of lumped-parameter model of surface circular foundation. The present method is an important extension to the concept of polynomial-fraction approximation in the foundation modeling. In the present analysis, the normalized flexibility function is adopted to improve the accuracy of the model and to reduce the parameters in modeling. The accuracy and validity of the lumped-parameter model is extensively investigated for the case of surface circular foundation. The proposed method may be easily applied to analyze various practical problems in soil-structure interaction such as vibration of machines on foundation and response of structures under earthquake.

Abstract: Methods of design and technological demands of construction are expounded for the structure with pre-stress tubular pile and anchor in the engineering of foundation pit. The design parameters for the pit are demonstrated by the means of FEM, and its feasibility is proved by the engineering practice. In the model of FEM, some pressure forces are imposed on the middle beam to simulate the anchor’s real mechanical properties. Taking into account the top ring beam and pre-stress tubular pile embedded each other very well, the straight beam element is adopted to simulate mechanical properties both of them. And the non-thickness interface element is also adopted to simulate the mechanical characteristics between the surrounding soil and the retaining structure, These experiences of design have important denotation for other similar foundation pit engineering.

Abstract: An experimental program of laboratory bearing tests was performed to characterize the bearing capacity of foundation on unsaturated granular soils. All tests were performed by pushing a circular rod on the surface of compacted sand specimens with different values of matric suction until failure. The test results show an increase in ultimate bearing capacity with increasing matric suction at low suction value but a decrease in that at high level of suction. The comparisons between the test results and simulations using the expressions proposed in this paper are presented and discussed. Good agreements are achieved for all testing values of suction.

Abstract: Deep mixing column (DMC) is a commonly used effective reinforcement in the treatment for Soft Foundation. In the DMC construction, due to the changes of strata, the work of the bit in mixing process will also change, then it lead to the electric current changes. By analyzing the construction process of DMC, This article proposes using the electric current method to control the DMC length in the soft foundation reinforcement, and through theoretical analysis and field experimental study, we conclude that it is a very good response to the depth of strata Changes through using the electric current numerical changes, when the electric current numerical value reaches a certain value, it meets the design requirements of the depth, then we should stop stirring the pile.

Abstract: At present, a lot of highway and railway development tend into use the bridge to replace of the road basis. It makes the construction of pile to be the core of the project. The hidden pile makes the construction to be more difficulty, but the technology of the ultrasonic texting improves the quality of the pile. Engineering practices have proved there has some closely relationship between the thickness of the end snaked grains and the pile supported strata stress.

Abstract: Take over-wet soil as research object, this paper presents the results of field test to verify the effect and feasibility of ash mixing method, one improvement technique for over-wet soil, on improving the performance of over-wet fill in construction site. This paper also studies the construction technology of utilization of over-wet fill in moist and rainy areas; determines construction parameters; summarizes construction techniques, methods and standards of quality control preliminary. The results show: ash mixing method can effectively improve the performance of over-wet fill; note that additives and over-wet fill should be fully stirred; this approach also works well for managing viscous silty sand.

Abstract: According to the similarity theory, this paper presents a similar model with the similar geometric load and boundary condition to analyze the difference between untreated over-wet soil in Ya’an and improved over-wet soil. The test results show: the bearing capacity of improved soil is enhanced; the settlement of improved soil is much less than which of unimproved soil; the water stability of improved soil is strengthened. These means we have achieved the purpose of improving over-wet soil and the ash mixing method is a feasible means for dealing with over-wet soil.

Abstract: Against loess landslide control, two physical model tests of loess landslide have been completed. Test I is model test of loess landslide with preset slide surface, loading on the top of the slope; test II is based on test I, adding the cantilevered anti-slide pile before the slope. The preset slide surfaces are composed of double-layer plastic films. Two testing processes and piling-up weights methods are the same; the only difference is adding cantilevered anti-slide pile and pressure cells placed around the piles. Through analyzing the results of the test I, similarity shear strength parameters of the preset slide surface are determined. In the test II, through analyzing soil displacement before the pile, limit state of loess landslide with the cantilevered anti-sliding model pile is established and load value is obtained, which provides references and bases for subsequent experimental study.

Abstract: Composite soils have been widely used in civil engineering applications, especially in slopes, embankment dam and landfills. This paper aims to investigate effect of fiber inclusion on shear stress of composite soil (i.e. sand composite). A series of laboratory direct shear tests carried out to evaluate fiber effect on strength behavior of composite sand. Clayey sand was selected as soil part of the composite and natural fiber was used as reinforcement. The fiber parameters differed from one test to another, as fiber length were changed from 20 mm to 50 mm and fiber content were varied from 0.5% and 6%.Normal stress kept constant at 200 kpa. For each test, stress_ displacement graph derived and the results were compared. The results proved that inclusion of fiber affected strength behaviour of sand composite so that increasing in fiber content and length caused increasing in shear stress.