Advanced Materials Research Vols. 261-263

Abstract: Nnumerical tests on three-dimensional failure process of rock samples containing vertical wall semi-arched tunnel with and without reinforcing are carried out with Mechsoft’s RFPA-Parallel system running on Lenovo 1800 Cluster, reproducing zonal disintegration phenomenon within rockmass around deep tunnels, and then the deep tunnel reinforcing influences on zonal disintegration within rockmass around tunnel is analyzed. Numerical results indicate that deep tunnel reinforcing does not change the general nature to form zonal disintegration phenomenon, but it can improve the stability of the tunnel wall.

Abstract: By numerical simulation approach, this paper analyzed a new construction method for over-cross tunnel. In this method one concrete framework and two connecting walls were used in the intersection zone to meet the requirement of ultra-close distance between the two tunnels: the lining of upper tunnel rode through on the lower one’s via two connecting walls. This paper conducted a series of study on the mechanical behavior of rocks and structures during the construction period. The stability of the structure and the feasibility of construction method were evaluated.

Abstract: Pile Dynamic Formulas are the oldest and frequently used method to determine bearing capacity of piles. The more recent method is based on the Wave Equation analysis and different formulations such as Case Mathod, TNO, CAPWAP and TEPWAP which were developed for pre-driving analysis and post-driving measurements applications. The major factors for the common use of the dynamic formulas have been due to their simplicity, cost effectiveness and applicability in various piling situations. However, in some literature the energy approach have been given an unfair reputation as being unreliable and less accurate than the more analytical or dynamic testing methods. One of the issues due to the poor performance of the dynamic formulas is that, historically, the hammer energy and the energy trasferred to pile had to be assumed. Nevertheless, with the advent of computers, new technologies are emerging with the advancement in construction industry. This has produced gradual improvements that have resulted in the dynamic method to be used on many projects with greater reliability. In this paper, a review of the different testing methods as well as pros and cons of the pile driving formulas are discussed. Also, an approach to improving the widely used Hiley dynamic equation is presented. This approach enables evaluation of the pile capacity to be made more accurately.

Abstract: The large talus landslide of is very complicated and difficult to deal with. In order to make a good research on the influence of rainfalls to the high talus slope deformation, the method of information entropy is employed by using the principle of information transfer and relativity to analyze and calculate the rainfall influence on the deformation velocity. Moreover, taking the full and accurate data of the accumulation body with high slope on the left bank in front of Xiaowan Dam as an example, the information transfer function between rainfall and deformation is established. The actual shows that this new method is convenient, universal and precise. It also demonstrates its great advantage for the analysis of such complex slope deformation problem that has a lot of influencing factors. The method does not make any hypothesis before putting into consideration.

Abstract: Liquefaction phenomenon which has produced severe damage all over the world was studied under earthquake record of 0.5g; one of the major effects of liquefaction is lateral spreading. Lateral spreading occurs in sloping grounds and can cause serious damage to structures and lifelines. The objective of this paper is to study the effect of earthquake shaking on soils and slope stability using Geo Studio software 2007. The applicability of the analysis is demonstrated by analysis various slope and embankments subjected to earthquake shaking. This study investigated the effect of embankment slope angle and its geometry on liquefaction. Pore water pressure can be increased by 100% to 35% as β ranged from 35ͦ to 45ͦ respectively, it can see that liquefaction zone induced by earthquake can eliminate as flattering slope and mean while reduced lateral speared displacement. Three case studies are providing to evaluation cyclic stress ratio (CSR) due to earthquake and lateral speared for soils.

Abstract: When highly weathered weak rock used to fill embankment, compaction character and wetting deformation character are major evaluation indexes. Based on California Bearing Ratio (CBR) test for highly weathered weak rock under different compaction degree, it was shown that the value of CBR increased as the increase of compaction degree. By means of dry-wet double curve parallel tests and wetting deformation experiments of different compaction degree of highly weathered weak rock under complex stress, the results indicated that when the degree of compaction is 90%, under rather high deviatoric stress, wetting can not only generate high additional axial deformation, but also cause fairly high additional volumetric strain and partial strain. And wetting cause shear intensity of soil reducing. So increasing the compactions of subgrade filling is the important way to reduce wetting deformation and to enhance slope stability of subgrade.

Abstract: For verifying pile bearing capacity improvement by post-grouting on tip and side and the decrease of building settlement, 10 tip and side post-grouting and 2 unpost-grouting piles are tested by low strain dynamic test, static loading test, stess distribution monitoring and high strain dynamic test, and the building settlement is monitored. It is indicated that all piles length and integrity are meeting the challenge, the post-grouting piles bearing capacity are at least 70% improved than that of unpost-grouting piles, designing pile bearing capacity as 8800kN is safer, the building maximal settlement and the differential settlement is satifying. The preliminary designed 904 piles are reduced to 531 by adopting post-grouting technique and about 20% cost of pile engineering is saved, the proper grouting stata choosing, the accurate grounting volume and pressure controlling in the post-grouting constrution process are needed.

Abstract: Considering the long-term atmospheric weathering effects on expansive soil strength, geogrid reinforcement effects of expansive soil slope are analyzed with FLAC3D. The research in this paper shows that: (1) when the reinforcement is deeper than the weathered layer, the inhibition effect of soil stress and displacement increases with increasing length of geogrid, in this case a critical slip arc moves away from the slope surface, and the maximum safety factor of slope stability increases approximately 50 percent; the grid stress decreases with the increasing height of grid location; (2) when the reinforcement depth exceeds the weathered layer 1 m, the denser geogrid in the vertical direction, the smaller shear stress and horizontal deformation in reinforced region, so that the slope safety factor increase and the critical slip arc moves towards the slope back. However,if the geogrid length exceeds the weathered layer more than 3 m, the vertical grid distance change has no significant influence on the safety factor and the location of critical slip surface.

Abstract: Elastic hinge model is one kind of reasonable models to analysis shield tunnel. However, no formulas are valid to calculate inner force caused by load of water pressure and elastic reaction. Mechanical equations of two kinds of load are built and inner force formulas are deduced. Results calculated by homogeneous ring model are contrasted with those by elastic hinge model and conclusion is derived. The contrast shows that the results according to elastic hinge model are more reasonable.

Abstract: Foundation treatment of expansive soils is a complex worldwide problem. Herein engineering behaviors of expansive soils and improved expansive soils with lime (IESL) in the runway area of Xinqiao international airport of Hefei were investigated by means of laboratory experiments and field tests. It was concluded that the expansive soils of mean plasticity index 24.2, and optimum moisture content of 16% in the engineering area, behaved weak and medium expansive potential. The plastic index of improved expansive soil of 7% lime mixed indoor and of 8% lime incorporated on site dropped to 20 and 13. At the same time, the free swelling ratios of IESL reduced up to 6.31 % and 3% relative to 46.5% of expansive soil, and the swelling pressure also decreased from 67.5 kPa to 4.05 and 11.28 kPa, respectively. The mean unconfined compression strength of improved expansive soil of 7 % lime on site was 853 kPa, 71% stronger of that of expansive soils. And the soil response modulus was up to 235.2 MN/m³, 9 times of expansive soils. It was also found form the immersion tests on site that the swell value of IESL was only 30% at most of expansive soils at the same depth. These results indicate that the compacted IESLs have a good bearing capacity, strength and water stability, so the engineering behaviors of IESLs are much better than those of expansive soils, and prove that the modification plan, expansive soils incorporated 7% lime on site could meet the design requirements.