Abstract: According to settlement of road-tunnel composite structure, relying on the Connecting Engineering Project at Shenzhen of Shenzhen-Hong Kong Western Corridor Project, settlement time series is analyzed by chaotic dynamics. Combining with phase space reconstruction, the correlation dimension, the maximum Lyapunov exponent, entropy and complexity of the road-tunnel composite structure system is studied. The results show that the settlement development of road-tunnel composite structure is still stable and predictable completely, of which chaotic characteristic is not obvious. This research has a great significance for the settlement prediction and control of the similar projects.
Abstract: Based on the principle of pedigree cluster, recursion formulae of distance between micro-structure parameters are given. Then, pedigree cluster method and corresponding process for loess micro-structure parameters are proposed to classify micro-structural characters of loess before and after collapsing. The study results indicate that micro-structures of loess before and after collapsing have significant cluster characters. The grain on horizontal section is considered as isotropic. Geometrical anisotropy of the grain on other sections is distinct. The proposed method can evaluate the difference of grains in study field in size, shape, deposition, direct, area distribution and grey distribution.
Abstract: There are more and more pit-in-pit excavations in cities, which include inner pit and outer pit. Owing to the inner pit excavation, pit-in-pit problem aroused and brought about accidents. For this reason, based on the co-construction, deep, and large pit-in-pit of Shanghai Museum of Natural History and Metro Line 13, the excavation influence between inner pit and outer pit was analyzed. The deformation of underground diaphragm wall under the condition of three different distances between outer pit and inner pit were compared through centrifuge model tests. Then, the effect of excavation width of outer pit on underground diaphragm walls was researched through numerical analysis. Results show that the deformation of outer underground diaphragm wall increased with the excavation width of outer pit, for the inner pit, the opposite was true. The critical influence distance between outer pit and inner pit was within 22 meter and 24 meter. According to the critical distance, the area adverse to excavation pit stability was identified.
Abstract: On the basis of the large soft soil foundation pit of Shanghai Expo axis and the Section 1 of underground complex project, this paper proposes the appropriate excavation procedure according to the results obtained by using centrifuge model tests and time hardening creep model, which uses ANSYS to compute foundation pit deformation caused by different excavation timeline, sequence and longitudinal excavation width of remained berm. The results of numerical calculation were approximately close to the horizontal displacement of the underground diaphragm wall measured both on site and from centrifuge model tests, so numerical calculation could well reflect the deformation behavior of excavation. The study also showed that more than 80% of underground diaphragm wall deformation caused by soil creep occurred within 60 days after the remained berm being excavated. In order to decrease the deformation, it would be useful to conduct plate structures as soon as the remained berm started being excavated. Remained berm and middle plate had good control over underground diaphragm wall deformation. When the remained berm was excavated by jumpily digging method, it would be advisable to firstly excavate the vicinity of underground diaphragm wall where there were no required protected objects nearby. The longitudinal excavation width of remained berm was proposed to be 20 meters in the north part and 30 meters in the south part.
Abstract: Gradually, anchor is in the working state of tension, but its stress becomes rather complicated when influenced by some external factors such as water, ground loads, etc. Aiming at the problems that ground additional load or coupling action of water and the additional load are forced on soil slope, the axial strain distributions of anchor tendons were obtained by model test. The change rules of axial strain at anchor head, near to slip plane, and end of the anchorage were analyzed respectively. The results show that under ground loads, the strain of anchor is biggest at the anchor head, and it gradually decreases from outer to inner. Under combined water and ground load, the stress state of the anchor system changes from tension to bending, and the upper anchors are most urgently affected. The experimental results can supply a reference for design and research of soil anchor with similar conditions.
Abstract: It is important of rock crack fine test for deep rock engineering. The high frequency part of Nyquist diagram of rock electrochemical impedance spectroscopy reflects the rock volume change characteristics, which can express the change information of rock internal cracks. With the topological theory, the topological characteristics of Nyquist diagram of sandstone, mudstone and granite are researched. The results show that the electrochemical impedance spectroscopy diagrams which come from the same size sample using the uniform test are isomorphism, and which can express using the same function. It shows the rock electrochemical process is regularity. At the same time, topological separation of rock electrochemical impedance spectroscopy diagram is researched. Fine change of rock crack can be detected with topological separation.
Abstract: The paper presents a numerical investigation of cracking of masonry wall with openings resulting from the asymmetry sedimentation of foundation. Two causes including end sedimentation and middle sedimentation are considered. The cracking process of the masonry wall with openings can be observed. The results indicate that different cracking patterns can be obtained with different sedimentation locations. Only oblique crack initiates and propagates when sedimentation occurs at end of the wall. A ski slope with the tips of the crack pointed outward can be obtained when sedimentation occurs at the middle of the wall.
Abstract: This paper adopts large diameter drill hole cast-in-place Pile of one Highway Bridge as the study case, using the pile calculatingly program, GPILE, that is a part of the common program software system of finite element method, SAP84, to analysis the pile group effect of large diameter drill hole cast-in-place Pile with different coefficients of pile group effect. This paper suggests using the ratio of the volume of pile and soil in the ambient range of pile group to express the new reduced coefficient and introducing the p-y curves of pile group after reduced as horizontal interaction model. Under these conditions, pile group nonlinearly effect of large diameter drill hole cast-in-place Pile is analyzed. At the same time, some different coefficients of pile group effects were calculated using this method. Compared these results, the feasibility and conciseness of reduced coefficient are testified.
Abstract: Based on thermodynamics theory and porous medium theory, the migration regularity of liquid water in the control layer of cooling roadbed is analyzed, and the influence of liquid water on the heat exchange between the control layer and the external environment is discussed. On the basis of the research results, the minimum thickness expression for the control layer is established, by which the liquid water could migrate and exchange heat in the control layer. The results indicate that within the regular thickness scope of design, the influence of water on the heat exchange between the control layer and the external environment could be neglected. The results can provide reference to the design and research for the control layer of cooling roadbed in cold regions.
Abstract: Prestressed Tubular Concrete pile (PTC pile) with individual cap is applied in soft ground treatment in the widening project of Jin-bin expressway. The observed data on embankment settlement, soil pressure, pore water pressure and lateral deformation, investigate the effect of the application of PTC pile in soft ground improvement for extension project of Jin-bin expressway in Tianjin soft area.