岩土工程技术

Studies on Unequal Acreage D—P Criterion Based on M-C Criterion and Its Application

MA Longxiang, YAO Hu

2010, 24(6): 271-276,286. doi: 10.3969/j.issn.1007-2993.2010.06.001

[Abstract](31) [PDF 787KB](5)

Abstract:
In order to overcome the shortcoming that Drucker-Prager yield criterions based on Mohr-Coulomb yield criterion lack of clear physical meanings, a new D-P criterion based on M-C criterion is proposed, which is called unequal acreage D-P criterion. The unequal acreage reflects the acreage of non-overlapping areas in the partial plane between M-C and D-P criterions. In the same partial plane, the smaller the unequal area is, the higher the degree of approximation of these two criterions is. The unequal acreage D-P criterion is a criterion that makes the unequal acreage with M-C criterion in the partial plane approximately smallest, so it is the most reasonable D-P criterion in these D-P criterions which is developed to approximate M-C criterion. Through analysis, the expression of unequal acreage in the partial plane between D-P criterion and M-C criterion is obtained. Then unequal acreage D-P criterion is given and Lode angle of the equivalent circle is also obtained. In addition, reduction factor of unequal acreage D-P criterion relative to external angle point circumcircle D-P criterion is given, so that the engineering application is made convenient. Finally, the unequal acreage D-P criterion is used in the slope analysis, and it is proved that the method is feasible.

Groundwater Level for Prevention of Up-floating Calculation and Effect Analysis

LI Zhengyi

2010, 24(6): 277-281,298. doi: 10.3969/j.issn.1007-2993.2010.06.002

[Abstract](64) [PDF 737KB](14)

Abstract:
This paper is proposed to establish a criterion for prevention of groundwater buoyancy on construction design,and give basis for site investigations.Further,with the formula for prevention of groundwater level up-floating,calculating and explaining the meaning of each factor of the most adverse conditions,and recommending technical basis of combination effects for groundwater level.According to the principle of hydraulic continuity,and on other relevant engineering technical conditions,commenting the risk of reduction of groundwater buoyancy on foundations built under an inferior seepage stratum,where the value for construction gravity should be chosen as a resistance during the analysis of foundation up-floating.In addition,the groundwater level parameters for prevention of up-floating could be relevant in other functions.

Influence of Different Factors on Hard Rock Brittle Failure in High In-situ Stress

WU Qingxing, LIU Bin, ZHANG Xiaoxin

2010, 24(6): 282-286. doi: 10.3969/j.issn.1007-2993.2010.06.003

[Abstract](33) [PDF 796KB](6)

Abstract:
The in-situ stress is obviously important to the stability of the underground opening in brittle hard rock.Previous researches generally focused on the brittle failure fashion and its prediction,the relation of the in-situ stress and the depth of brittle failure is extremely insufficient.In the paper,based on the brittle failure criterion,the relationship between the different in-situ stress environment,opening shape and the depth of brittle failure d_f have been analyzed by Examine2D software.Conclusions can be drawn as follows:with the increase of principal stress ratio k value,d_f shows increase trend in the form of line in the low minimum principal in-situ stress,in the form of non-line in the high minimum principal in-situ stress and damaged region diverge the direction of the minimum principal stress to the angle of 45° between the minimum in-situ stress.The influence of the direction of principal stress is lower than the value of the principal stress when tunnel's length similar to width.The site of brittle failure is different with different tunnel shape in the identical in-situ principal stress environment,but the depth of brittle failure is minor.Stress concentration factor in different excavation shape is different.The depth of brittle failure effectively reduced when the prolate axis vs minor axis equal to the k in ellipse cavern.

Discussion on the Pressure Calculation of Surrounding Rock with Structural Plane

LIU Fuchen, WANG Hongqun

2010, 24(6): 287-289. doi: 10.3969/j.issn.1007-2993.2010.06.004

[Abstract](22) [PDF 681KB](5)

Abstract:
There are many structural planes such as joints, faults, weak intercalations, strata planes, schistosity and gneissic schistosity in the rock mass. The different combinations of structural planes form the structural bodies of vary formations and sizes. This paper gives out the calculation models and comparations to two groups and multi-groups structural planes of the same tendency and two groups structural planes of the anti-tendency. We finally obtain the profitable conclusions with different combination of dip angle and vary calculation conditions.

Laboratory Test on Improving High Plasticity Soft Soil with Vacuum Preloading Combined Electroosmotic

CAO Yonghua, HOU Jinfang, GAO Zhiyi

2010, 24(6): 290-293. doi: 10.3969/j.issn.1007-2993.2010.06.005

[Abstract](26) [PDF 714KB](7)

Abstract:
It is difficult to improve high plasticity soft soil with conventional drain consolidation methods such as vacuum preloading or surcharge preloading. Large scale laboratory test was conducted to study the feasibility of improving this kind of soft soil with vacuum preloading combined electroosmotic. The vacuum preloading was used to improve the soft soil firstly. When the consolidation degree reached 80%, the electroosmotic started. The current, electric potential and surface settlement was monitored in the test. The result revealed that pole reversal and intermittent current were effective to improve the efficiency of the power. After the test, the strength of the soil increased from 0-0.7 kPa to 18.2-26.2 kPa and the electroosmotic was very helpful to improve the strength in the later stage of the test.

Accident Analysis and Treatment of Deep Foundation Pit in Shanghai in Soft Soil About One Pumb Gate

LIN Lixiang, ZANG Guangwen, HE Zailiang

2010, 24(6): 294-298. doi: 10.3969/j.issn.1007-2993.2010.06.006

[Abstract](41) [PDF 822KB](6)

Abstract:
Gates Foundation introduced a pump displacement and steel pile supported retaining the force process, causing instability of the reasons for supporting a detailed analysis, design and construction process of excavation problems, introduced after the emergency shoring unstable, envelope reinforcement, reinforcement and support system impervious reinforcement measures, while disposal of reinforcement reinforcing effects are analyzed, draw relevant conclusions and recommendations for similar pit provided some basis for the smooth construction.

Field Experimental Study on Deformation Monitoring of Foundation Pit

ZHU Zhanyi, WANG Yongwen, ZHANG Kaiwei

2010, 24(6): 299-303. doi: 10.3969/j.issn.1007-2993.2010.06.007

[Abstract](27) [PDF 812KB](5)

Abstract:
Based on the deformation monitoring of foundation pit of zhong-hong-tian-di business-living building, in Tongxiang city, Zhejiang province. And soil-compacting during the pile-sinking construction is studied. The area is about 120 times of it's edge-length can come up uplift deformation, when the piles with 40 cm edge-length were pressed. And the variation of differential settlement of people-living houses around the foundation pit is analyzed. The stress state of retaining structure is changed, which causes the retaining structure appears floating phenomenon, during excavation of foundation pit. The horizontal displacement of soil becomes large in pace with the excavating depth of foundation pit, moreover, under the action of soil creep deformation, the horizontal displacement will become more large. In case of rainfall, groundwater level head inside and outside of foundation pit will increase, at the same time, basement retaining structure side pressure will increase, too. Support axial force can be affected by solidification contraction of concrete, temperature difference, different creep of concrete and reinforcement. So the support axial force should be modified.

Application of Seismic Reflected Wave Method in the Geotechnical Engineering Investigation

WANG Xia, MA Xiaoyue

2010, 24(6): 304-306,323. doi: 10.3969/j.issn.1007-2993.2010.06.008

[Abstract](29) [PDF 752KB](7)

Abstract:
Because of the weakness in determining of the mud layer waving situation in traditional drilling exploration, we always use the shallow seismic reflected wave method in some retaining dike to determin the mud layer's waving situation. From the reflectional geophysical prospecting image of this water area, we know that there's a absolute line between slit layer and clay layer. There's a clear reflective wave in 30m,and it can be easily seem the moving situation of the bedrock surface. Compared with the drilling information, geophysical prospecting is more accuracy, and meets the requirment of this project. It shows that the shallow seismic reflected wave method is the fast, efficient new method in water project geophysical prospecting. It has the broad application prospects in a variety of geotechnical engineering investigation.

Database Establishment of CPT and Correlation Analysis of Soil Parameters

XU Jiacheng, CHEN Zuyu, WANG Yujie

2010, 24(6): 307-311. doi: 10.3969/j.issn.1007-2993.2010.06.009

[Abstract](36) [PDF 784KB](10)

Abstract:
CPT is widely used in the field in-situ tests with good continuity, reproducibility and reproducibility, but its digital management and the study of correlation is still little. The CPT database what not only has the characteristics of large information content, simple operation, code open and so on, but also has the advantage that the analysis result is more reliable as the data is more abundant, was established by Excel VBA. Based on the experimental data of geotechnical engineering investigation come from 18 projects in Shanghai in CPT database, three groups of relationship formula of specific penetration resistance Ps and soil compression modulus E₀, consolidated-quickly shear indicators(c_cq、φ_cq) and triaxial consolidation draining shear indicators(c_cu、φ_cu) are got by correlation analysis. Test of significance shows that:these formulas can be used as engineering design reference in some areas that are similar to Shanghai.

Difference Analysis of the Reinforcement Treatment on Reclaimed Soil Foundation in Coastal Region

ZHANG Yuting, DONG Haijun

2010, 24(6): 312-314. doi: 10.3969/j.issn.1007-2993.2010.06.010

[Abstract](21) [PDF 690KB](5)

Abstract:
In land reclamation, the sediment in the sea is hydraulic filled to the land making area. In the process of reinforcement, the hydraulic fill is non-uniform that the settlement, pore-water pressure and soil strength has difference on reclaimed ground.The cause of difference and the regularity of parameters variation has been analyzed. Moreover, the proper suggestions has been given.

Reinforcement Strategies and Geological Features of Dangerous Reservoirs in Panyu District of Guangzhou City

WANG Qiguo, YANG Hanliang

2010, 24(6): 315-319. doi: 10.3969/j.issn.1007-2993.2010.06.011

[Abstract](19) [PDF 941KB](4)

Abstract:
There are 15 reservoirs still yield benefits in Panyu District of Guangzhou City, which 12 reservoirs in danger disease, urgent need for reinforcement. Based on geological survey and assessment work, identification of the area's geological features dangerous reservoirs:dam body of poor quality, dam leakage and infiltration and sabotage the problem exists, soft ground deformation and earthquake liquefaction of saturated sand, etc, of the entire insurance reinforced engineering measures, such as heightening and strengthening dam, seepage control, anti-earthquake liquefaction and so on. The results for the area to provide technical support for remediation dangerous reservoirs, water conservancy project on the whole similar risks internally reinforced with a good reference value.

Safety Assessment on Tilting-column Supported Aisle in Scenery Zone

WANG Yaowu

2010, 24(6): 320-323. doi: 10.3969/j.issn.1007-2993.2010.06.012

[Abstract](22) [PDF 1150KB](3)

Abstract:
Most of the tilting-column supported aisle which without formal design is overcrowding. Based on the parameters obtained from field survey,there are eight structural patterns summarized. It is found that for a tilt-columned supported aisle structure,the maximum moment and shear forces come into being in the horizontal beam,and the maximum axial force exists in the tilt rod. The maximum internal force models are set up after structure analysis. It is proposed that the structure is safe if the visitors walk separately and intervals a distance of more than 0.5m. But consider the actual needs of tourism,a slope of support can be added.

2010 Vol. 24, No. 6