5.3 Water Retaining Structure
5.3.1 The types of water retaining structures shall be determined after techno-economic comparison on the basis of topographical and geological conditions，dam height，building material，operating conditions，construction conditions，construction duration，construction quantities and investment，etc.
5.3.2 The layout of gravity dams shall meet the following requirements:
1 Gravity dams should be built on rock foundation，but low dams may be built on solid sand and gravel foundation or soil foundation.For a low gravity dam built on a weak foundation such as soft clay，reliable measures must be taken for foundation treatment.
2 The layout of flood discharge，water diversion，power generation and sediment releasing structures in the dam body shall avoid interferences with each other.
3 For a rolled concrete gravity dam，the layout of dam structures shall be favorable for construction of roller compacted concrete.
4 To meet the requirements for strength，stability against sliding，permeation resistance and durability of dam foundation，the foundation treatment measures shall be designed such as consolidation grouting，curtain grouting and water drainage，etc.
5 According to different working conditions and local climates in various zones of the dam，concrete construction of the dam shall be designed by zones，so as to meet the requirements for the strength，permeation resistance，frost resistance and abrasion resistance of dam body.
5.3.3 Analysis and computation of the stability against sliding and the stress of dam foundation shall be conducted for gravity dams.For a gravity dam not located on a rock foundation，analysis and computation of seepage and settlement shall also be conducted.
5.3.4 The layout of arch dams shall meet the following requirements:
1 Arch dams should be built on the site with relatively narrow valley and good geological conditions.
2 The axis of an arch dam should be fixed upstream of thick and stable rock mass on both banks of the river valley.
3 The shape of arch dam shall be designed with full consideration of the dam body stress and the stability requirement of arch abutment.Priorities shall be given to the arch shapes with variable curvatures，such as parabolic，elliptical or log spiral shapes，while the maximum central angle of horizontal arch ring should be 75°-110°.
4 If there are local deep grooves on the riverbed of dam site，the arch dam should be designed with abutment.If the upper part on both banks of dam site is an open area or the engineering geological condition is relatively poor，a gravity pier or thrust pier should be set up to connect with the arch dam.(https://www.daowen.com)
5 The stress and stability of arch dam shall not be unfavorably impacted by the layout of any structure of the project.
5.3.5 For arch dams，the stress of dam body and the stability of arch abutment shall be calculated and analyzed.
5.3.6 Earth-rock fill dams may be built as homogeneous dam，zoned dam or artificial anti-leakage material dam depending on the following conditions:
1 Types，properties，quantities，locations，excavation and transportation conditions of dam building materials and usage of excavated spoils.
2 Layout of project，topographical and geological conditions，method of foundation treatment，connection of dam body with water releasing and diversion structures，and seismic intensity，etc..
3 Construction diversion，flood prevention，meteorological condition，construction condition and progress schedule.
5.3.7 If the storage or quality of natural impervious material cannot meet requirements or its use is uneconomic，artificial materials such as asphalt concrete，reinforced concrete and geo-textiles may be used in the anti-seepage works of the dam body.
5.3.8 For earth-rock fill dams，computation and analysis shall be made on the stability against sliding，seepage and settlement according to the type and height of dam.
If a thick toe slab（thicker than 2m）or a high toe wall is used in a concrete face dam or there is weak intercalation in the foundation rock under the toe slab，the stability and stress of the toe slab shall be analyzed and calculated.
5.3.9 Rubber dams should be built on river reaches where the river course is smooth and straight，the riverbed and bank slopes are stable and there is little sediment，and the dam should not be higher than 5m.Rubber dams should be designed jointly with sluices.
5.3.10 For water retaining structures to be built on rock foundations，the design of foundation treatment and their connections with bank slopes shall meet the requirements for strength，anti-slide stability，stable seepage，bypass seepage and durability.
5.3.11 For water retaining structures to be built on non-rock foundations，in the design of its foundation treatment，the engineering measures such as blanket，cutoff wall and foundation replacement should be taken.For the foundation treatment of deep overburden strata，measures such as high pressure jet grouting，concrete cutoff wall and vibro-flotation may be taken，so as to meet the requirements for strength，deformation，anti-seepage，drainage，reduction of differential settlement，and anti-scouring，etc.
