【Daily Discussion】Water Resources and Hydropower Engineering-20200714

The waterproofing is not properly done, and the dam lacks sufficient strength and stiffness during construction

1.1.1 Porous seepage: Seepage that occurs as water flows through the pore spaces in soil and rock materials; it is generally a uniform flow within the pores, and the amount of seepage depends mainly on the particle size distribution of the soil and rock materials as well as their permeability coefficients. Such as loess, sand layers of various particle sizes, and gravel, etc. 1.1.2 Fractural leakage: Leakage that occurs as water passes through the joints and fractures in soil and rock materials. When joints and cracks are complex, fractured seepage approaches a uniform flow regime ； When joints and cracks develop irregularly, fracture seepage exhibits a non-uniform flow pattern. The amount of fissure leakage depends on the degree of development of joints and fractures. 1.1.3 Pipe-type leakage: Leakage that occurs when water flows through cavities in soluble rocks. The magnitude of the pipe-type leakage depends on the size of these underground cavities. For example, in reservoirs located in karst areas, water seeps through caves of various sizes.

①The filling quality does not meet the standard requirements; the compaction is not sufficient, and at the joints, inadequate compression or leakage results in poor bonding between the layers. ②The construction soil has poor quality, high water permeability, and a mixed composition. ③Damage caused by external factors, such as destructive animals. ④The dam body is not sturdy enough, and no effective water retention measures have been implemented.

The main reasons may be: ① The filling quality does not meet the standard requirements; the compaction is not sufficient, and the joints between layers are not tightly bonded due to incomplete or insufficient compression at those areas； 　　②The construction soil has poor quality, high water permeability, and a mixed composition ； 　　③Damage caused by external factors, such as destructive animals ； 　　④The dam body is not sturdy enough, and no effective water retention measures have been implemented.

The reasons are: (1) Due to factors such as the small size and thinness of the dam body, the seepage line escapes from the dam slope above the downstream drainage area, resulting in scattered seepage.   (2) Due to an unreasonable design of the impermeable barrier, permeation failure occurred in it.   (3) Concentrated leakage occurred due to unreasonable design and construction of the culverts embedded within the dam body. (4) The dam fill contains too much sand and gravel, resulting in high permeability; or the fill is not compacted properly, leading to a large seepage gradient and thus seepage erosion.   (5) When the dam body is filled in layers, the soil layers are too thick, resulting in inadequate compaction; moreover, the joints between these soil layers are not properly compacted.   (6) Animals such as termite badgers and rats dig holes inside the dam to build nests, creating concentrated pathways for surface seepage. (7) Vibrations such as gunshots on the mountains near the area where fishing was being done prior to the earthquake caused penetrating transverse cracks in the dam body or seepage layers, resulting in leakage.   (8) If the dam foundation or the slopes on both sides are not properly treated, lateral cracks can form due to differences in settlement levels, allowing water to seep through. Backflow of floodwater downstream can block the drainage system, raising the level at the points of overflow and causing water to seep out along the dam slopes.  

First, the soil used for dam construction is of poor quality; for example, it contains impurities and has high permeability. As a result, it cannot be compacted properly during construction； Second, the thin dam body results in an excessively short seepage path ； Third, the drainage system below the dam is blocked and ineffective, or no drainage system is provided at all ； Fourth, water leakage from the originally sealed gaps below the dam ； Fifth, termites build nests within the dam structure, causing damage.

The main reasons may be: ① The filling quality does not meet the standard requirements; the compaction is not sufficient, and the joints between layers are not tightly bonded due to gaps or insufficient compression at those areas. ② The soil used for construction is of poor quality, highly permeable, and has a mixed composition； ? ③ Damage caused by external factors, such as destructive animals ； ?④ The dam body is not sturdy enough, and no effective water retention measures have been implemented.

The main reasons may be: ① The filling quality does not meet the standard requirements; the compaction is not sufficient, and the joints between layers are not tightly bonded due to gaps or insufficient compression at those areas. ② The soil used for construction is of poor quality, highly permeable, and has a mixed composition； ? ③ Damage caused by external factors, such as destructive animals ； ?④ The dam body is not sturdy enough, and no effective water retention measures have been implemented.

The reasons are: (1) Due to factors such as the small size and thinness of the dam body, the seepage line escapes from the dam slope above the downstream drainage area, resulting in scattered seepage. ? (2) Due to an unreasonable design of the impermeable barrier, permeation failure occurred in it. ? (3) Due to unreasonable design and construction of the culverts embedded within the dam body, concentrated leakage has occurred. (4) The dam fill contains too much sand and gravel, resulting in high permeability; or the fill is not compacted properly, leading to a large seepage gradient and thus seepage erosion. ? (5) When the dam body is filled in layers, the soil layers are too thick, resulting in inadequate compaction; moreover, the joints between these soil layers are not properly compacted. ? (6) Animals such as termite badgers and rats dig holes inside the dam to build nests, creating channels through which seepage occurs. (7) Vibrations such as gunshots on the mountains near the area where fishing was being done prior to the earthquake caused penetrating transverse cracks in the dam body or seepage layers, resulting in leakage. ? (8) If the dam foundation or the slopes on both sides are not properly treated, lateral cracks can form due to differences in settlement levels, allowing water to seep through. Backflow of floodwater downstream can block the drainage system, raising the level at the overflow point and causing water to seep out along the dam slopes.

1) Due to reasons such as the small size and thinness of the dam body, the seepage line escapes from the dam slope above the downstream drainage structure, resulting in scattered seepage. ? (2) Due to an unreasonable design of the impermeable barrier, permeation failure occurred in it. ? (3) Due to unreasonable design and construction of the culverts embedded within the dam body, concentrated leakage has occurred. (4) The dam fill contains too much sand and gravel, resulting in high permeability; or the fill is not compacted properly, leading to a large seepage gradient and thus seepage erosion. ? (5) When the dam body is filled in layers, the soil layers are too thick, resulting in inadequate compaction; moreover, the joints between these soil layers are not properly compacted. ? (6) Animals such as termite badgers and rats dig holes inside the dam to build nests, creating channels through which seepage occurs. (7) Vibrations such as gunshots on the mountains near the area where fishing was being done prior to the earthquake caused penetrating transverse cracks in the dam body or seepage layers, resulting in leakage. ? (8) Poor treatment of the dam foundation or the slopes on both sides