天然应力比系数<img src="https://static.zxtiku.com/wangke/imgs/topic/24dd3b0fe0631cc83707b2e591e8631f.jpg"/>中( ) A. <br/> <img src="https://static.zxtiku.com/wangke/imgs/topic/0693caa99b8981b8cb864940950281a5.jpg"/>随深度增加而减小, B. <br/> <img src="https://static.zxtiku.com/wangke/imgs/topic/0693caa99b8981b8cb864940950281a5.jpg"/>随深度增加而增加 C. <br/> <img src="https://static.zxtiku.com/wangke/imgs/topic/0693caa99b8981b8cb864940950281a5.jpg"/>不随深度变化 D. <br/> <img src="https://static.zxtiku.com/wangke/imgs/topic/0693caa99b8981b8cb864940950281a5.jpg"/>与深度Z成正比