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Register a new userEffect of a stiff thin Foundation soil layer’s depth on dynamic response of an embankment dam
دراسة تأثير تغير عمق طبقة تربة عالية القساوة ذات سماكة قليلة في أساسات سد على استجابته الديناميكية (حالة سد زيزون)
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Tishreen University ورقة بحثية
Publication date
2015
fields
Geotechnical Engineering
and research's language is
العربية
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Shamra Editor
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حدث انهيار سد زيزون في عام 2002 و هو سد ترابي يتوضع في الشمال الغربي من الجمهورية العربية السورية. و كان لهذه الحادثة وقع كبير في زيادة الوعي لأهمية و حساسية اجراء التحريات الجيوتكنيكية اللازمة لمواقع انشاء السدود خاصة و ان هذه التحريات لم تعطى الاهتمام الكافي في مراحل السابقة اضافة الى الدراسة الزلزالية والظروف الجيولوجية لموقع السد. يقع سد زيزون في نطاق نظام فالق البحر الميت مما يشدد على اهمية تحليل استجابة موقع السد و بالتالي دراسة تأثير التطبقات الليتولوجية في أساسات السد على استقراره في الحالة الديناميكية. هذا البحث يعنى بدراسة تأثير طبقة تربة عالية النفوذية تتميز بمواصفات ستاتيكية و ديناميكية مختلفة عن طبقات التربة المحيطة بها و تتواجد على أعماق متغيرة ضمن أساسات السد كما في حالة سد زيزون مع الأخذ في الحسبان أن هذه الطبقة تصل إلى عمقها الأصغري عند الموقع الذي حصل فيه انهيار السد [Rehabilitation of Zeizoun dam and the appurtenant structures. 2005]. تم اعتماد برنامج GEO-STUDIO في إجراء الدراسة التحليلية لهذا البحث ، و هو برنامج جيوتكنيكي يعتمد على طريقة العناصر المحدودة و التحليل الرقمي للنماذج التحليلية للرشوحات و الاجهادات و الاستقرار بالحالتين الستاتيكية و الديناميكية. بينت نتائج التحليل الديناميكي ارتفاعا في منسوب خط الرشح في جسم السد, تضخيم في الاستجابة الديناميكية, زيادة في ضغط الماء المسامي المتولد بتأثير الحركة الزلزالية (excess pore water pressure) و انخفاضا في عوامل الامان على الاستقرار, تمت دراسة و رصد كل النتائج السابقة من خلال بناء عدة نماذج تحليلية يختلف كل منها باختلاف عمق الطبقة النفوذة عالية القساوة ضمن اساسات السد.
In 2002, Zeyzoun Dam failure, that is an embankment dam located at the northwest of Syria, made a big Awareness of the effects of the lack of Geotechnical investigations and concern given to seismic design, geological conditions and location of the dam. Zeyzoun dam location, in the vicinity of the Dead Sea fault system, emphasizes the importance of analyzing the effects of lithological stratum in dam foundations on dam seismic stability. This paper is concerned with the influence of a high permeable soil layer that has different static and dynamic properties, and exists at different depths in dam foundation. Geo-studio software, a Geotechnical program that applies the finite element method and can consider analysis like seepage, dynamic analysis and slope stability, used to build and analyse numerical models. The results of dynamic analysis showed rising of phreatic line level in dam body, amplification in dam dynamic response, increasing in pore-water and excess pore water pressure and decreasing in stability factors of safety, along with decreasing of the thin layer depth.
References used
Rehabilitation of Zeizoun dam and the appurtenant structures. AGROCOMPLECT, PLC. Sofia, Bulgaria. 2005
BATHE, K.J. Finite Element Procedures in Engineering Analysis. Prentice-Hall. 1982
KOKANEH, S.P. et al. Seepage evaluation of an earth dam using Group Method of Data Handling (GMDH) type neural network: A case study. Scientific Research and Essays Vol. 8(3), pp. 120-127. 2013
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It was found in this research that the seismic response of the
structure increases with the decrease in the shear waves velocity in
the soil, and the seismic response of the structure increases with
soil layer thickness between the foundations of the structure and
bedrock depth.
Therefore in this paper we will present the stability analysis carried out on the
Dwesat dam with vertical core, its high is 33m, the downstream slope of 1V:2.75H and the
upstream slope of 1V:3.0H. Thickness of the vertical core was varied from 1V:
0.25H to
1V:2.0H, and also present the effect of the varied thickness on slope stability for both
upstream and downstream under three design conditions i.e. during and end of
construction, steady state seepage and rapid draw down by General Limit Equilibrium
Method using GeoStudio software.
It was observed from the analysis that by varying the thickness of vertical core of
earth dam, thinner core up to 1V:1.30H gives more stability and further increase in
thickness of core tends to sharp decline in factor of safety for both upstream and
downstream slope under different design conditions.
In this research, a study of full tank case is carried out. The water
contained in the tank was modeled as two masses following the
recommendations of Eurocode.
This research includes analytical study by Finite Element Method about the effect of
earthquakes in the stability of ALBASEL DAM, so we have set a numerical model suitable
by using programs Slope/W, Quake/W. We run the model and we got the results
of the
simulation, which summarized in calculation factors of safety for verification the final
stability of the dam under the effect of different intensity earthquakes. And then were
compared between the two cases static and dynamic model showing the effect of the shear
variables of the soil angle of internal friction and tendency of slops dam and the different
situations of the lake water levels and the high of dam in addition to the effect of the
construction material of the dam on the stability of the body of the dam.
After the study each case depending on the parameters, that are entered, and based
on the resulting factors of safety, the diagrams are painted to appear the positive or the
negative effects to increase or decrease any variable of the dam variables in each of the
static case and the dynamic case. And then we studied the effect of seismic Amplification
resulting from the body of the dam on both the two horizontal and vertical component of
seismic acceleration. The results will help us in a perfect choice for variables of
Embankment dams for design.
The stability of the upstream shell of the dams is changed under the rapid drawdown
condition where the pore water pressure has a different values according to the soil
permeability. This paper considers the stability of the upstream shell of the "
Braddon" dam
with many types of soil and analyses each type under two rapid drawdown programs, the
first program is when the discharge happens, according to the irrigation outlet by 25 m3/s,
and the second program is when the discharge happens according to the tunnel conversion
of the river by 500 m3/s. The obtained results show, that the stability of the upper slope
under considered boundary conditions changed according to the soil type. Some soil have
good stability factor while other soil collapsed .Accordingly, we can conclude that the
type of soil of the upper dam slope is important and we could chose the appropriate type
which does not cause dangerous during the rapid drawdown. Also the study shows that:
the highest values of the safety factors result when the slopes are formed of high
permeability soils as well as the slopes of homogeneous soil, while the soils formed of
materials between them appeared decreasing values of safety factors.
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