diff --git a/B06_Section/B06_Section_UI_Cross_Design.ts b/B06_Section/B06_Section_UI_Cross_Design.ts
index 900f9c2c5..47e973173 100644
--- a/B06_Section/B06_Section_UI_Cross_Design.ts
+++ b/B06_Section/B06_Section_UI_Cross_Design.ts
@@ -24,7 +24,10 @@ import type {
   SectionMode,
   SectionSample,
 } from "./B06_Section_Api_Fetch";
-export { appendPavementOverlay } from "./B06_Section_UI_Cross_Design_Surface";
+export {
+  appendPavementOverlay,
+  appendRockBoundaryOverlay,
+} from "./B06_Section_UI_Cross_Design_Surface";
 
 const SVG_NS = "http://www.w3.org/2000/svg";
 
diff --git a/B06_Section/B06_Section_UI_Cross_Design_Surface.ts b/B06_Section/B06_Section_UI_Cross_Design_Surface.ts
index cf6419403..b35b73912 100644
--- a/B06_Section/B06_Section_UI_Cross_Design_Surface.ts
+++ b/B06_Section/B06_Section_UI_Cross_Design_Surface.ts
@@ -2,6 +2,33 @@ import type { CrossDesign } from "./B06_Section_Api_Fetch";
 
 const SVG_NS = "http://www.w3.org/2000/svg";
 
+export function appendRockBoundaryOverlay(
+  svg: SVGElement,
+  samples: Array<{ offset_m?: number; elevation_m?: number | null; valid: boolean }>,
+  offsetM: number,
+  x: (offset: number) => number,
+  y: (elevation: number) => number,
+): void {
+  const segments: string[][] = [];
+  let current: string[] = [];
+  for (const sample of samples) {
+    const elevation = sample.elevation_m;
+    if (sample.valid === false || elevation === null || !Number.isFinite(elevation ?? NaN)) {
+      if (current.length > 1) segments.push(current);
+      current = [];
+      continue;
+    }
+    current.push(`${x(sample.offset_m ?? 0)},${y((elevation as number) + offsetM)}`);
+  }
+  if (current.length > 1) segments.push(current);
+  for (const points of segments) {
+    const polyline = document.createElementNS(SVG_NS, "polyline");
+    polyline.setAttribute("points", points.join(" "));
+    polyline.setAttribute("class", "b06-chart__rock-boundary");
+    svg.append(polyline);
+  }
+}
+
 export function appendPavementOverlay(
   svg: SVGElement,
   design: CrossDesign,
diff --git a/B06_Section/B06_Section_UI_Cross_View.ts b/B06_Section/B06_Section_UI_Cross_View.ts
index 85343d197..8ae48e147 100644
--- a/B06_Section/B06_Section_UI_Cross_View.ts
+++ b/B06_Section/B06_Section_UI_Cross_View.ts
@@ -26,6 +26,7 @@ import { appendRevetmentOverlay, computeRevetmentLayout } from "./B06_Section_UI
 import {
   appendCrossDesignOverlay,
   appendPavementOverlay,
+  appendRockBoundaryOverlay,
   type RockBoundaryControl,
 } from "./B06_Section_UI_Cross_Design";
 import { appendCardFooter, appendCardHeader } from "./B06_Section_UI_Cross_Card_Chrome";
@@ -488,6 +489,16 @@ export function createCrossSectionCard(
       // 사토장(유용토운반작업장) — 교본 6장 3절이 횡단도 표시를 요구한다. 값은 설계 결과에서
       // 그대로 오고 여기서 다시 세지 않는다. 선 종류는 터파기 파선과 갈라 둔다.
       appendSpoilFillOverlay(plotLayer, section.design, x, toDisplayY);
+      // 암 경계선 = 지면선 복사 + 오프셋(계획선 기준 아님).
+      if (rockBoundary && section.design.geometry_preset === "rock") {
+        appendRockBoundaryOverlay(
+          plotLayer,
+          drawSamples,
+          rockBoundary.offsetFor(section),
+          x,
+          toDisplayY,
+        );
+      }
       // 배수관 세트 — 조정창이 쓸 카드 상태를 받아 둔다(2026-08-19) · 링크 카드도 채운다(2026-08-24).
       culvertInletIsBasin = !!culvertLayout?.basin;
       culvertHiddenPipe = culvertLayout?.culvert.hidden_pipe === true;
diff --git a/B06_Section/B06_Section_UI_Style_Cross_Areas.css b/B06_Section/B06_Section_UI_Style_Cross_Areas.css
index 4e6925180..146e3a085 100644
--- a/B06_Section/B06_Section_UI_Style_Cross_Areas.css
+++ b/B06_Section/B06_Section_UI_Style_Cross_Areas.css
@@ -168,6 +168,16 @@
   pointer-events: none;
 }
 
+/* 암 경계선(설계선 복사 + 오프셋): 리핑암·발파암 구간 점선 */
+.b06-chart__rock-boundary {
+  fill: none;
+  stroke: var(--color-warning);
+  stroke-width: 1.6;
+  stroke-dasharray: 6 4;
+  stroke-linejoin: round;
+  opacity: 0.9;
+}
+
 /* 포장층 박스: 노면 양 끝점 기준 두께만큼 하향 채움 */
 .b06-chart__pavement {
   fill: color-mix(in srgb, var(--color-text-secondary) 30%, transparent);
@@ -291,6 +301,13 @@
   fill: var(--color-text-secondary);
 }
 
+/* 유입 보호공 공간 확보 절토선 — 말단에서 표준단면 절토경사로 지반까지 */
+.b06-chart__culvert-cut {
+  stroke: var(--color-warning);
+  stroke-width: 1.4;
+  stroke-dasharray: 5 3;
+}
+
 /* 기슭막이 돌 해칭 — 기운 띠 안에 한 줄로 쌓인 큰 돌(실무 도면 형상) */
 .b06-chart__culvert-stone {
   fill: none;