Advanced Materials Research Vols. 243-249

Abstract: The settlement of each part of the composite foundation, such as the foundation mat, cushion, soils and pile head, is recognized as equivalent under normal working conditions. On the basis of this, the corresponding load on long-short pile and soils can be derived easily from each individual p-s curve. The p-s curve of the composite foundation can be pictured in terms of the mutual actions of all the components mentioned above. and thus the corresponding settlement with load will be determined. Meanwhile, the p-s curve can be obtained via the undisturbed soil hyperbola tangent modulus method, which not only characters the nonlinear relationship between load and settlement very well, but also shows the deformation compatibility among those components. It is found that designed bearing capacity of soil is much higher than the reality based on usual design norms of composite foundation, while pile load is greater than the designed ones, which can be credited to the deformation compatibility of pile-soil not considered.

Abstract: A case history of a deep multi-strutted soft clay excavation in Hangzhou is presented in this paper. What makes it particular interest is its three characteristics: large scale, deep excavation and very soft clays. The excavated area was about 99750 square meters. The depth of excavation was 12.85 m. 4 m below the ground surface located about 24 m very soft soil clays. Wall deflections and ground settlements were measured and compared with similar case histories worldwide. It was shown that the maximum horizontal deformations of the excavation was very large which this excavation reached to 220 mm. “Creep” deformations occurred apparently during the curing of the bottom slab of the basement. The distributions of the surface settlements seemed to be parabolic, and the settlement influence zone could reach to a distance of more than 2H, where H is the final excavation depth. The ratio between the maximum ground settlement and the maximum horizontal deformation of the wall is about 0.6.

Abstract: In order to get anti-dynamic load capabilities of solidified bodies with soil stabilizer which is a kind of hydraulic cementing material, tests were carried out on three sorts of solidified bodies under contact explosion. According to three different sorts of solidified material objects of soil, sand and detritus, three groups’ pieces of solidified bodies were prepared. Tests above show that anti-dynamic load capabilities of solidified bodies are at least two times than raw materials, and the capability of soil solidified body is the best than the others.

Abstract: The direct shear mechanical characteristics of soil-structure interface under different experimental condition were studied systematically using the DRS-1 high normal stress direct and residual shear apparatus. The results show that the normal stress is an important factor which determines the mechanical characteristics of soil-structure interface. The curve of shear stress-shear displacement presents strain softening when the normal stress<3MPa, linear hardening when =3~5MPa and strain hardening when12MPa, separately. At the same time, the volume of the soil expands when <3MPa and contracts when >3MPa. But the volume of the soil expands and contracts simultaneously during the process of direct shear when =3MPa.The roughness of the interface influences not only the shape of the shear stress-shear displacement curve but also the shear strength of the interface. Under same normal stress condition，the shear strength of interface increases with the roughness but the influence degree of interface roughness reduces gradually with the increase of normal stress. The grain breakage degree is different under different normal stress. It increases evidently with the increase of normal stress.

Abstract: Taking deep excavation engineering in North Region of Senlin Park Station of Beijing Olympic Subway branch as engineering background, deformation law of enclosure structure of deep excavation are studied by the in-situ monitoring means .It shows that the maximum horizontal displacement of retaining pile is closely related with excavation depth and time. When the deep foundation pit is excavated to a certain depth, and steel brace hasn’t been erected, horizontal displacement of the pile tops is maximum. The location of the maximum horizontal displacement shifts down with foundation pit excavation and steel brace erection. With steel brace application, steel axis force decrease, so steel brace can effectively control horizontal displacements of retaining pile and internal force of steel in the pile. In addition, temperature has a certain effect to axis force of steel brace.

Abstract: This paper obtains function index system of excavation by FAST method and introduces two-class fuzzy comprehensive evaluation to estimate function index system. By analyzing the excavation's life-cycle costs obtains the evaluation method for excavation design cost, proposing new evaluation standards for excavation design. At last establishing value engineering (VE) evaluated model for excavation design, and put it into engineering practice to prove that the model is convenient and practical, simple, fast, and accurate.

Abstract: During the hydraulic structure design, the stability of abutment slope is critical to the normal operation of hydraulic structure. Through the tests, the effects of different hydraulic pressure on the strength and deformation characteristics of sandstone were studied, and the variation characteristics of rock masses with joints under secondary loading after excavation damage were analyzed as well. Test results show that: 1. When the samples without immersion secondly load until complete failure, ultimate strain increases slightly than the first loading, of which the increasing value is 7.5%; elastic modulus has a relatively large reduction than the first, which reduces 22.8%; deformation modulus has a less reduction, which is about 3.3%; 2. When considering the softening action of different hydraulic pressure on samples, ultimate strain increases by about 23% than that without consideration of immersion effect; elastic modulus reduces about 53%; deformation modulus reduces about 39%; 3. With the increment of immersion pressure, sample strength decreases greater, so does the softening effect of water on rock samples. With the increment of pressure, the strength of rock with joints has a relatively large reduction, which is from 27% to 41%, and the increasing value of intact rock mass isn't great, which is only from 25% to 27%. Jointed rock masses are more sensitive to the softening effect of water, and mechanical properties weaken obviously after long-term immersion with unstable problem.

Abstract: Compare with horizontal support, the bracing systems of pile and oblique brace have obvious advantages in deep excavation. However, because diagonal brace is inconvenient for the construction of structure , the use of this system is limited. Based on the coordinating space role of this support system, planning the excavation and exchanging brace and construction structure as a whole, according to the minimum potential result of a piecewise space unit, this paper introduces the model which are both applied to the excavation stage and exchanging brace stage, and derives the calculation method in relationship to the length of sub region. optimal design of the whole process was proposed for this form. Finally, the feasibility and rationality of the proposed method was verified by the practical engineering. And reached some signifecative conclusions, these can provide reference for the design and construction of such supporting system.

Abstract: The bracing systems of pile and oblique bracing have obvious advantages in big and deep excavation. Because the study about the removal of oblique bracing is rare, the use of this system is limited. This author would study the transfer of internal forces and deformation issues in the process of the exchanging support through an example, from the design and construction, and the result will be verified through the measurement. The study has showed that the removal of such bracing shall tack the coordinating role of space in account, and use the collaborative computing method to remove the diagonal braces in several subregion and sections. And reached some interesting conclusions, these can provide reference for this design and construction.

Abstract: This paper mainly introduced the monitoring scheme of one mine’s wind well in Inner Mongolia. By analyzing the monitoring data at different depth, rules of the freezing temperature field were drawn. Fitting the monitoring data linearly at freezing and thawing phrase respectively, the experience formula of time prediction at the two phases were obtained. Meanwhile the temperature diffusion coefficient of sandstone and mudstone layers were revised, which can provide scientific basis for some similiar shaft construction.