Seepage Patterns in an Earth-Rock Fill Dam Evaluation using Electrical Resistivity Tomography (ERT) Method

Seepages in the earth-rock fill dam are usually monitored by pore pressure, seepage water table, and seepage discharge. However, those monitoring are difficult to describe the seepage patterns because they are installed only in certain points. This research evaluated the seepage pattern resulting from Electrical Resistivity Tomography (ERT). The resistivity was measured by installing electrodes upstream of the Dam at every 10 m and downstream at 20 m distances. The seepage pattern was analysed from the resistivity 2 Dimension distribution using the RES2DINV program. The results showed that the seepage pattern resulting from the ERT method’s resistivity data, which was compared with data of surface dam deformation, pore pressure, and seepage water table, could explain the seepage discharge data. Based on those confirming data, the resistivity data of the ERT method was appropriate to explain the seepage pattern in the earth-rock fill dam and can be further utilized for dam stability analysis.

Effects of core characteristics on seepage through earth dams

In this research, SEEP2D and SEEP/W numerical models are used to simulate seepage through earth dams with internal cores. In order to evaluate the two models' performance, they were compared in cases with no, vertical, and wedge-shaped cores. SEEP/W was then used to study further cases due to its accuracy in drawing the phreatic line within the core zone. The effect of the core's characteristics on the amount of discharge, and the phreatic line's levels at the core's upstream and downstream faces were investigated. Four core types – vertical, wedge-shaped, upstream inclined, and downstream inclined – were considered. Different hydraulic conductivities, upper widths, and core slopes were also evaluated. The wedge-shaped core is the most effective of those investigated in reducing seepage discharge and the phreatic line's level at the core's downstream face, the vertical core came second. Design equations are provided for all the core shapes considered in the study.

Angka Keamanan Piping di Bawah Tubuh Bendungan dengan Metode Harza

Dams have many benefits such as irrigation, flood prevention, power generation and even tourism, especially in areas where the dam is located. So that the benefits received can last a long time, in the planning, it must be analyzed for stability, seepage discharge that occurs and the safety of the piping. The piping hazard safety figures in this study were calculated using the Harza method for maximum water level conditions, normal water levels, fast receding and empty dams at sta 0 + 150, sta 0 + 200, sta 0 + 250 and sta 0 + 300. Based on the calculation results, it is found that the safety of piping hazards without filters with the grouting method do not meet the requirements safety factor, especially in conditions of maximum water level, normal water level and fast receding. In order for the safety of piping hazard in order to meet the requirements, a filter is applied under the dams. The filter is applied so that the piping hazard safety figure meets the requirements of all water level conditions and all station is 80 cm deep. Keywords: safety factor, piping, Harza method, filter ABSTRAK Bendungan memiliki banyak manfaat seperti irigasi, pencegah banjir, pembangkit listrik bahkan pariwisata khususnya pada wilayah dimana bendungan tersebut berada. Agar manfaat yang diterima dapat berlangsung lama maka dalam perencanaannya wajib dianalisis terhadap stabilitas, debit rembesan yang terjadi maupun keamanan dari piping. Angka keamanan bahaya piping pada penelitian ini dihitung dengan menggunakan metode Harza untuk kondisi muka air maksimum, muka air normal, surut cepat dan bendungan kosong di sta 0+150, sta 0+200, sta 0+250 serta sta 0+300. Berdasarkan hasil perhitungan didapatkan bahwa angka keamanan bahaya piping tanpa penggunaan filter dengan metode grouting tidak memenuhi persyaratan angka keamanan khususnya pada kondisi muka air maksimum, muka air normal dan surut cepat. Agar angka keamanan bahaya piping memenuhi persyaratan maka diaplikasikan filter dibawah tubuh bendungan. Filter yang diaplikasikan agar angka keamanan bahaya piping memenuhi persyaratan diseluruh kondisi muka air dan seluruh sta adalah dengan kedalaman 80 cm. Kata kunci: angka keamanan, piping, metode Harza, filter Abstract Dams have many benefits such as irrigation, flood prevention, power generation and even tourism, especially in areas where the dam is located. So that the benefits received can last a long time, in the planning, it must be analyzed for stability, seepage discharge that occurs and the safety of the piping. The piping hazard safety figures in this study were calculated using the Harza method for maximum water level conditions, normal water levels, fast receding and empty dams at sta 0 + 150, sta 0 + 200, sta 0 + 250 and sta 0 + 300. Based on the calculation results, it is found that the safety of piping hazards without filters with the grouting method do not meet the requirements safety factor, especially in conditions of maximum water level, normal water level and fast receding. In order for the safety of piping hazard in order to meet the requirements, a filter is applied under the dams. The filter is applied so that the piping hazard safety figure meets the requirements of all water level conditions and all station is 80 cm deep. Keywords: safety factor, piping, Harza method, filter ABSTRAK Bendungan memiliki banyak manfaat seperti irigasi, pencegah banjir, pembangkit listrik bahkan pariwisata khususnya pada wilayah dimana bendungan tersebut berada. Agar manfaat yang diterima dapat berlangsung lama maka dalam perencanaannya wajib dianalisis terhadap stabilitas, debit rembesan yang terjadi maupun keamanan dari piping. Angka keamanan bahaya piping pada penelitian ini dihitung dengan menggunakan metode Harza untuk kondisi muka air maksimum, muka air normal, surut cepat dan bendungan kosong di sta 0+150, sta 0+200, sta 0+250 serta sta 0+300. Berdasarkan hasil perhitungan didapatkan bahwa angka keamanan bahaya piping tanpa penggunaan filter dengan metode grouting tidak memenuhi persyaratan angka keamanan khususnya pada kondisi muka air maksimum, muka air normal dan surut cepat. Agar angka keamanan bahaya piping memenuhi persyaratan maka diaplikasikan filter dibawah tubuh bendungan. Filter yang diaplikasikan agar angka keamanan bahaya piping memenuhi persyaratan diseluruh kondisi muka air dan seluruh sta adalah dengan kedalaman 80 cm. Kata kunci: angka keamanan, piping, metode Harza, filter

Investigation and Practical Application of Silica Nanoparticles Composite Underwater Repairing Materials

Repairing materials are well-known to play an important role in rehabilitating and extending the service life for hydraulic concrete structures. However, current underwater repairing materials possess several problems, including insufficient bond tensile strength, inconsistency with the deformation of the old substrate, and insufficient underwater self-sealing ability. In the present paper, an experimental study was carried out to evaluate the influence of silica nanoparticles (SNs) on the properties of underwater composite-repairing materials. The underwater deformation, impermeability, bond tensile strength, and compressive strength of the SN-modified underwater composite-repairing materials were used as the properties’ evaluation indices. The results show that, within a certain range, the performance of the repairing material increase with increased SN percent. The deformability, impermeability grade, underwater bond tensile strength, and compressive strength of the SN-modified composite underwater repairing materials are 2.2%, 8, 2.91 MPa, and 115.87 MPa, respectively, when the mass ratio of the mortar, the curing agent and the SNs is 8:1:0.002. The proposed material is employed to repair the dam for a hydropower station in Guizhou province, China. Results show the seepage discharge is reduced by 8.6% when the dam is repaired. The annual average generating capacity is increased by 1.104 × 105 kWh. Meanwhile, CO2 and NOx emissions are reduced by 1.049 × 105 and 220.8 kg annually, respectively.

The Influence of Damage to the Geomembrane Layer on the Seepage Pattern and Discharge at the Homogeneous Embankment Dam

Placing the geomembrane layer on the upstream slope can control the seepage in homogeneous dams. Poor geomembrane design, construction and maintenance caused damage to the geomembrane that caused a leak through the dam body. This study discusses the effect of damage on the geomembrane layer at the homogeneous embankment dam on the seepage pattern and discharge. The study location is in the Sianjo Anjo dam, Aceh Singkil district, a homogeneous dam with a geomembrane layer located in the dam body's upstream part. The damage of the geomembrane layer is assumed caused by the various defect of locations and size. The results show that the seepage pattern (phreatic line) tends to be weak in the geomembrane layer without damage. Meanwhile, if the geomembrane layer is damaged, the larger the defects' width, the higher the phreatic line. However, the seepage pattern that occurs shows insignificant or almost the same. The seepage discharge increases with increasing defect width and decreasing defect location

Fluctuation Effect of Reservoir Water Level on the Seepage of Earth-Fill Dam

Lots of dam failures are the result of uncontrolled seepage. The collapse of the Situ Gintung Dam in Tangerang, Banten-Indonesia in 2009 due to heavy rains caused the dam structure to collapse. This is due to increased pore water pressure in the landfill. To anticipate collapse due to uncontrolled seepage, it is necessary to monitor it based on the behavior of changes in rainfall and reservoir water levels. Seepage within the dam body is often monitored using instrumentation tools such as standpipe piezometer (standpipe piezometer) or electric piezometer. But often the piezometer cannot work properly because it is clogged, so it cannot monitor the condition of the seepage. Other instrumentations such as V-Notch are also used to measure seepage discharge. This study aims to determine the behavior of changes in the reservoir water level caused by changes in rainfall and its effect on body seepage of the earth-fill Type dam. By knowing the phenomenon of the behavior of the relationship between reservoir water infiltration and rainfall, it will obtain information on rainfall that endangers the dam which will affect the downstream. In this study, a case study of the Selorejo Dam was taken which has a large enough reservoir capacity of about 31 million m3 which is included in the Brantas River Basin. The results showed that 5 piezometers devices were damaged (SL 1, SL 2, SL 4, SL 6, and SL 7) where they could not read the phreatic water level properly, and 2 piezometers were less sensitive to reading fluctuations in reservoir water levels. namely SL 10 and SL 11 which showed R2 values of 29.78% and 39.4%, respectively. While the maximum seepage discharge is recorded at 1474 liters/minute, this is still below the critical discharge of 1630 liters/minute allowed for this dam, but this needs to be a concern, especially the discharge from toe drain from the left side seepage and C-area which is the leakage from the left support pedestal also contributes a larger discharge than other observation points.

Analysis and Estimation of Seepage Through Earth Dams with Internal Cut Off

The study of seepage through earth-fill dams is very important for the constructed dams to ensure that the control of seepage is sufficient for the safe and sustainable operation of the dam. It is also important in the design and construction of new dams to ensure that the seepage through and under the dam will be well controlled. Construction horizontal, inclined, trapezoidal or pipe filters one of the dam protection methods. Cut off also can be constructed to minimize seepage discharge directed to the downstream face of the dam. Seepage through an earth dam with internal cut off is experimentally studied in the laboratory of Irrigation Engineering and Hydraulics Department, Faculty of Engineering, Alexandria University, Egypt on a Hele-Shaw model. Also, using computer program SEEP/W (which is a sub-program of Geo-Studio). The experimental and numerical analyses of seepage through earth-fill dam with internal cut off is conducted. Results from solutions are compared with each other.

Seepage losses from trapezoidal earth canals with an impervious layer under the bed

Seepage of irrigation water from earth canals is one of the most significant causes of water loss. It should be carefully studied and controlled. This research aims to study the effect of the presence of an impervious layer under the bed of trapezoidal earth canals on the amount of seepage discharge. The finite element numerical model SEEP2D is used in the study. Different scenarios for the canal's dimensions and side slopes are considered. Various values for the vertical distance between the canal's bed and the impervious layer are also studied. The numerical model's results are verified using Vedernikov's equations. The results show that the presence of an impervious layer can reduce the amount of seepage discharge by up to 82.7% compared to that calculated without it, depending on the depth of the pervious layer, the ratio between canal's bed width to water depth, and the side slopes. It is recommended to have boreholes at canal construction sites in order to investigate if an impervious layer exists under the canal's bed. This helps to estimate the correct amount of seepage discharge based on the vertical distance from the canal's bed to the impervious layer under it. Design charts are also provided.