Mosul Dam between the threats of imminent collapse

This research deals with the state of Mosul Dam since first filling of the reservoir, studying the salt measurements and quantity of grouting materials consumption against drilling bore holes lengths. Based on those measurements, the conclusion made that, the state of the dam had been passed prior periods more dangerous cases than it is now, specially before fixing 319m level as threshold level in which the Reservoir level not admitted it be higher. The conclusion made that the state of the dam currently is not the worst case as claimed by USA side the research also explained the most important methods of maintenance and controlling which needs to follow according to design and guidance of treatment. The most important conclusion that this research raise is the necessity of construction of the Diaphragm Wall as a permanent solution which can be considered as a unique solution to solve the Mosul Dam problems permanently.


. History of the dam
Project was planned since 1950 under the name of (Askikalak Dam) by the Iraqi Development Board. Mosul dam was designed by a Swiss consultant (a group of Swiss consultants) and implemented by (GIMOD) (German Italian Mosul Dam JV). Start construction at 1980 and Tigris River was closed in 1984 while filling the reservoir started in spring of 1985 until completion in 1985. The grouting Gallery was constructed during the implementation of the dam to be ensure the dam foundation grouting and constructed according to design, and start grouting of the foundation before the main structure was built, No negative signs have been reported concerning the dam body and its function construction within more than 30 years. Dam construction has been completed in 1986 [1].

. The main purposed to be constructed Mosul dam
The main purposed to be constructed Mosul dam are Flood control, to prevent the areas located south of it from the danger Water Regulation of the irrigation uses provide drinking water to the urban dwellers. The dam also serves to generate hydroelectricity with maximum1050 MW Environmental improvement and developing fish resources. Also, the collect water during the time when the resources is available and release it during the dry period, in order to provide a cost-effective method of storing larger volumes of water for livestock or irrigation [1].

Location
Mosul Dam is located on the Tigris River 50 km north of Mosul city in Nineveh governorate [1].

Site Geology
• Changed several times, and several geological investigations and preliminary designs were conducted and not decided until 1974 [3] . • At 1978 the location of current site of the dam axis were subjected to a new of extensive and detailed geological investigations. • All the consultants who worked on that investigations and designs agreed on the difficulty and complexity of the foundation in all the investigated sites because of the presence of highsolubility gypsum rocks in the water .

Beginning of the Problem
a) The beginning of problem starts since the construction of the dam and its operations, it has been shown that dam was constructed on a foundation of soluble gypsum, and that require continuous treatment by grouting deep [4]. b) The Seepage from the foundations of the dam appeared during the first storage in 1985 . c) In 1986, also, the Seepage appears near the spillway and increased more than 800 liters / Sec. d) It was recommended to start grouting within the foundation before the superstructure was built.
Blanket-grouted 25 m deep around the foundation and a curtain 150 m directly below the dam. e) The Grouting was carried out several times to reduce the seepage which still at this point, and its quantity changes with the changes of storage level. This seepage does not represent the leakage through the body of the dam, or the total leakage of the dam foundation. f) Grouting started with beginning of storage and implemented by a secondary contractor (Keller -Rokem Radio). g) Several parts of the dam such foundations, D/S the dam and spillway which grouted had been well-considered and conform to design requirements according to depth of water storage [4]. h) A hole was discovered in a curtain in one of the areas that take so long time to be closed by grouting, in 1987, a decision was made to deepen the curtain and change the grouting mixture with the injection and changing pressures with it. i) In 1988 the Iraqi staff began receiving all grouting work of the injection, filling, mixing and operating and maintaining of the machines. [4].

Analysis of the large loss that appeared in the tourist city in 2003:
• Feb 2003: Big sink holes appeared in the tourist area and was closed by earth fill material but was developed and a settlement of buried material noticed. Continuity of settlement led to concentrate the grouting work [5].
• To prevent the continuity of settlement development, the drilling and grouting machine Shifted from the left side to the right side were the sink hall appeared. Because of less efficiency's and shortage of the machineries and with shortage of grouting material, the efficiency of grouting work as a total has been affected negatively. • In July 2005, another land settlement in the downstream of the dam between the area main spillway and the Fuse block 60m from the edge of the dam are take place and was treated by increasing the grouting work effort.

Actions taken after 2003
The measures below have contributed significantly to the monitoring and maintenance and development of injections and grouting and then the safety of the dam up to date: In the first years after 2003, many important steps taken: • Provide the grouting materials and repair the idle machines and provide spare parts.

Evaluate the efficiency of the Grouting
It is concluded that the geological nature of the foundations of the dam is complex and contains layers of gypsum and anhydrite with a high solubility in water. Therefore, in order to strengthen the foundations, it is necessary to create a deep curtain and install a wide network on both sides of the curtain for the purpose of monitoring and evaluation, to take necessary actions for its restoration and maintenance to ensure dam safety. Method of evaluation according to the following equation: Note: Mainly if the degree of efficiency is less than 50% means the curtain needs to be treated and re-injected, the above evaluation has helped greatly in continuing to carry out the treatments in a timely manner and in order to ensure the safety of the foundation of the dam and thus the safety of the dam.

Discussion -Analysis of the results of measurements for Seepage and soluble Salts:
The table below shows the quantities of grouting material injected into foundation for sections points ( 1,3, and grouting tunnel) shown on the image below , which representing from year 1986 until 20o5, the information of which is also included in the final report submitted in 2005 by the (Washington international .inc ( group [2].   The total consumption of grouting material (ton/m) of drilling during the period  indicates that the cavities for 2015 are lower than in previous years, whereas in 1998 it was the largest consumption of grouted material from all other years. This shows that the dam is currently not in the most dangerous cases as pointed out in the report of the American side, and even more serious cases in previous years have been overcome by treatment with grouting materials injection [5] 9  • It can be deducted from available data and charts which available, that the years (2015, 2014, and 2013) founded the greatest consumption of grouting material and then the more dangerous than the current material even that the continuous grouting overcome the risk. • In order to study the consummation in relation with drilling quantities: • If the drilling is equal to or less than the consumption means there are few cavities.
• If the drilling is equal to or more to the consumption means there are more cavities. From above quantities we can concluded when the risk was greater and when the dam threatened the possibility of collapse.
• By studying the charts and using the relation mentioned above, it deduces when the dam has a high probability of collapse • Also noted from the above charts that the grouting work during in 2014 as was relatively reduce by 42% Each a large dam should has monitoring system, including Cameras, geological investigation drilling, permeability test for grouting holes, grouting consumption visual inspection, seepage measurement in addition to chemical mater test. All these test and monitoring measurements can give impression on state degree of any emergency alerted by measurements of these devices and thus indicate the need for immediate treatment by the grouting and this is what happened and happens since the beginning of operation and so far and can't collapse suddenly without prior indications. 3. The presence of experts and special machines for drilling grouting and pumps is necessary to implement the program of grouting and overcame the emergency situations. Continuous grouting is necessary to avoid accumulation of cavities and the occurrence of irregular settlement in the dam as a result of the occurrence of the collapse. The grouting does not represent a permanent solution to avoid the risk situation, but the implementation of a concrete cut-off (Diaphragm) required with depth till end of gypsum layers (About 180m depth). 4. Minister of Water Rescuers Signed a contract with a foreign company to construct the grouting work because of the lack of financial possibility to implement the concrete (Diaphragm), which represents a permanent solution to the Problem. 5. The construction of the concrete diaphragm represents perm ant solation which will finish al Mosul dam problems. 6. Till the starting of construction of diaphragm requires the following must be done • Assess and identify risks and set standards for this.
• Evaluate the reduction of the reservoir level and the action diaphragm taken previously.
• Increase monitoring and inspection based on the operation and maintenance manual and the instructions of the designer and consultant. • Update the emergence plan of Mosul dam. 7. Important phenomena that require focusing and considering their appearance require an immediate response, whether need reduction of the level, as well as an emergency grouting process: a. The sudden changes in the reading of measurement of the piezometers and the monitoring of advises and also check the chemical analyzes of the water of the reservoir and the piezometers and taking periodic, all these will indicate geodetic. Survey and gives indications of the development of a state of cases.