The shoulder collapse stems from insufficient dam end restraint and uneven stress. The internal anchoring strategy, through "pulling onto the bank wall, locking it inside the wall, and smooth transition", transforms the ends of the dam bag from suspended in air into continuously and securely anchored inside the wall, thus completely solving the problem of wrinkles and collapse.

I. Why Does Dam Shoulder Collapse?

End shoulder collapse mainly occurs at the junction of the dam bag and the pier/bank wall, manifesting as: 
- Insufficient bulging of the dam bag ends after filling with water, insufficient height, and excessive internal pressure.
- Rounded corner collapse, wrinkling, overflow.
- Root causes: Insufficient end restraint, excessive friction, unreasonable anchoring lines, and weak end cap stiffness.
Common contributing factors:
1. Anchorage shoulder collapse: End cap folding, uneven stress, local pull-out.
2. Resistance shoulder collapse: High side wall friction, obstructed end expansion, increased internal pressure, and deformation collapse.
3. Geometry and stiffness: Insufficient end perimeter, excessively sharp corners, and poor side cap stiffness.

II. How Does In-wall Anchoring (Bank-Wall/End-Wall anchoring) Solve Shoulder Collapse?

The core idea is to "pull the end of the dam bag up to the wall, lock it inside the wall, ensure a smooth transition, and distribute the force evenly," changing from "plugging and squeezing for waterproofing" to "full-length anchoring + wall-surface bonding for waterproofing".
1. Anchoring lines are moved from the "base plate end" to a continuous arrangement within the wall and base plate.
- Traditional: Anchoring is only done at the base plate end, leaving the plug suspended under pressure and prone to collapse.
- In-wall anchoring: The anchoring line extends upwards along the base plate wall surface, forming an L-shaped/zigzag continuous anchoring.
– Effects:
 - The end tension is distributed to multiple rows of anchors within the wall, not concentrated at the base plate end.
 - The dam bag adheres tightly to the wall surface, preventing bulging and collapse.
 - Sufficient end circumference and controllable deformation during filling. 
2. End dam bag "wall-wrapped + in-wall anchoring" eliminates suspended end cap.
- The dam bag end bypasses the wall corner and adheres to the inside of the end wall/bank wall, firmly fixed with pre-embedded bolts/pressure plates/wedges within the wall.
- The plug changes from a "free pressure-bearing body" to a tension-bearing edge adhered to the wall surface, eliminating suspension, folding, and localized high pressure. 1. Waterstopping changes from "plugging and squeezing" to full-length, seamless sealing, resulting in low friction, easy expansion, and no collapse.
3. Multiple rows of anchors within the wall + gradual transition ensure uniform stress and prevent wrinkles.
- Multiple rows of anchors are installed within the wall, with increased spacing, releasing tension step by step.
- The anchoring line transitions smoothly at the wall base (rounded/oblique angle), avoiding right-angle wrinkles and stress concentration.
- The dam bag fits smoothly and seamlessly against the wall surface, without bulges or collapse.
4. Increased end perimeter + reserved length within the wall compensates for deformation.
- Sufficient dam bag length is reserved in the anchoring section within the wall, and the end perimeter is increased by 10%~20%.
- Sufficient extension space is provided at the end during water filling, preventing tension, collapse, and ensuring the correct height.

III. Summary in One Sentence

In-wall anchoring transforms the dam bag end from a "suspended plug at the bottom plate end" to a "continuous, close-fitting anchor within the wall." By moving the anchor line upwards, securing it within the wall, using multiple rows of gradual changes, and increasing the perimeter, it eliminates suspension, reduces friction, and distributes stress evenly, fundamentally solving the problem of shoulder collapse.

IV. Comparison (Traditional Anchoring vs. In-wall Anchoring)

- Traditional Anchoring: Bottom plate end anchoring, suspended plug, high friction, prone to shoulder collapse, water overflow

- In-wall Anchoring: Continuous anchoring between wall and bottom, close to the wall with no suspension, low friction, no shoulder collapse, good water-tightness