-
Analytical Elastoplastic Solutions for Deep-buried Circular Tunnels Under Asymmetric Load
Zhang Xin,
Zhang Xiangping,
Wang Zhang,
Lang Min,
Zhao Suzhi,
Du Yuxiang,
Sun Jinshan
Issue:
Volume 9, Issue 2, March 2021
Pages:
31-38
Received:
5 January 2021
Published:
12 April 2021
Abstract: The elastoplastic analysis of the surrounding rock of a circular tunnel is a very classic rock and soil mechanics problem. Previous scholars usually studied the situation under axisymmetric load, and they usually did not take the non-axisymmetric load distribution under the influence of ground stress and lateral pressure into account, which greatly affected its application in engineering practice. Approximate analytical solutions for calculating the plastic zone range, stress field and displacement field of the surrounding rock of a circular tunnel are inseparable from the consideration of the strength reduction and volumetric dilatancy characteristics of the rock material. The elastic-softening-residual plastic triple linear stress-strain model and the Mohr-Coulumb failure criterion are involved. The approximate analytical solutions of the residual stress field, strain field, displacement field and radius of the plastic zone in the elastic zone, plastic softening zone and surrounding plastic zone of the circular tunnel surrounding rock under axisymmetric load are deduced. The analytical solutions are valid only when the plastic zone is large and the lateral pressure coefficients 1≤λ<3. The approximate analytical method is close to the calculation result of finite element method and can replace the finite element method to carry out simple elastic-plastic analysis of surrounding rock.
Abstract: The elastoplastic analysis of the surrounding rock of a circular tunnel is a very classic rock and soil mechanics problem. Previous scholars usually studied the situation under axisymmetric load, and they usually did not take the non-axisymmetric load distribution under the influence of ground stress and lateral pressure into account, which greatly...
Show More
-
Modeling Sediment Yield-Case Study Guder Watershed, Blue Nile Basin, Central Ethiopia
Gonfa Erena,
Dereje Adeba
Issue:
Volume 9, Issue 2, March 2021
Pages:
39-46
Received:
9 February 2021
Accepted:
24 March 2021
Published:
23 April 2021
Abstract: Guder watershed is one of the watershed found in Blue Nile basin, central Ethiopia, mostly eroded area due to the widespread of agricultural land. This study is based on the Soil and Water Assessment Tool (SWAT) model interface of GIS environment to simulate sediment yield of the watershed at outlet. The stream flow was calibrated for ten years (1996-2005) and validated for seven years (2006-2012) at Guder gauging station using SWAT-CUP to check performance of the model. The model performance has been evaluated by using statistical parameters of coefficient of determination (R²) and Nash-Sutcliffe simulation efficiency (NSE) 0.92 and 0.80 respectively for calibration. Model validation results 0.83 and 0.65 for R² and NSE, respectively. Both calibration and validation results indicate that the measured values show good agreement with simulated flow. Sediment yield from each sub watershed were determined and prone soil erosion areas has been identified for management planning.
Abstract: Guder watershed is one of the watershed found in Blue Nile basin, central Ethiopia, mostly eroded area due to the widespread of agricultural land. This study is based on the Soil and Water Assessment Tool (SWAT) model interface of GIS environment to simulate sediment yield of the watershed at outlet. The stream flow was calibrated for ten years (19...
Show More
-
Experimental Study on Interface Strength Between Hardened Cement Paste-Aggregate
Wenliang Han,
Hongfa Yu,
Haiyan Ma
Issue:
Volume 9, Issue 2, March 2021
Pages:
47-54
Received:
9 March 2021
Published:
26 April 2021
Abstract: The interfacial transition zone (ITZ) is a weak part of concrete, which is the main reason that the mechanical properties of concrete are far lower than those of hardened cement paste and aggregate itself. In order to improve the mechanical properties of concrete ITZ, the effects of cement varieties, water-binder ratio, mineral admixtures and aggregate types on the strength of hardened cement paste-aggregate ITZ were studied by orthogonal test. A linear regression model between interfacial bonding splitting tensile strength and splitting tensile strength of hardened cement paste was proposed. The results show that the water-binder ratio has the greatest impact on the mechanical properties of ITZ, followed by aggregate. The interfacial bonding splitting tensile strength of five kinds of aggregate and cement paste is in the order of marble > coral > granite > basalt > quartzite. The optimal interface test combination is as follows: water-binder ratio 0.25, aggregate is marble, P•O52.5 cement, slag content 15%, fly ash content 20% and silica fume content 10%. The optimal cement slurry combination is: water-cement ratio 0.25, basic magnesium sulfate cement, slag content 15%, fly ash content 20% and silica fume content 10%. The linear regression model between interfacial bond splitting tensile strength and hardened cement paste splitting tensile strength is established by dividing aggregate, which is of great significance to study the law of interfacial strength.
Abstract: The interfacial transition zone (ITZ) is a weak part of concrete, which is the main reason that the mechanical properties of concrete are far lower than those of hardened cement paste and aggregate itself. In order to improve the mechanical properties of concrete ITZ, the effects of cement varieties, water-binder ratio, mineral admixtures and aggre...
Show More
-
Cause of Construction Material Wastage on Public Building Project in Western Oromia
Garba Wokjira Fayisa,
Shiferaw Garoma Wayessa
Issue:
Volume 9, Issue 2, March 2021
Pages:
55-62
Received:
13 February 2021
Accepted:
29 March 2021
Published:
26 April 2021
Abstract: In the construction industry, construction material is one of the major cost components and it is 50% to 70% of the total construction cost. However, the industry generates 30%-65% of wastage for landfill. Effective use of construction material is profitable in the industry as well as in the economy of any country. However, material wastage management in construction are rarely studied by Ethiopian context. Hence, this research is aimed to investigate cause of construction material wastage and rank highly wasted construction material wastage on public building projects in western Oromia. The Study uses both primary and secondary data by structured questionnaires and case study (interviews and site visits). The research has covered a population of General and Building contractors from level one to three and their supervisor’s that are employed in western Oromia on public buildings. The purposive sampling techniques were used to collect the data and Analyzed and presented by mean score by using statistical package for social science (SPSS) and excel worksheets. The result of the study analyses, mostly causes of construction materials are; Changes made to the design while construction is in progress, Lack of attention paid to dimensional coordination of products, Damage during transportation, Improper planning for required quantities, Designer’s inexperience in method and sequence of construction. In addition, causes of construction material wastages are presented under seven attributes causes. As well as wastage of material on eight key construction, material are ranked as concrete, wooden formwork, block, and steel are most wasted by asking respondents based on their experience in the construction industry. Generally, wastage of material is highly occurred in every activity i.e. during design, construction and during the production of the material.
Abstract: In the construction industry, construction material is one of the major cost components and it is 50% to 70% of the total construction cost. However, the industry generates 30%-65% of wastage for landfill. Effective use of construction material is profitable in the industry as well as in the economy of any country. However, material wastage managem...
Show More
