城关区地质灾害防治规划.doc

城关区地质灾害防治规划
several group number, then with b ± a, =c,c is is methyl b two vertical box between of accurate sizrrors, specific method is from baseline to methyl vertical box center line distance for a,, to b vertical box distance for b, list can measured
several group number, then with b ± a, =c,c is is methyl b two vertical box between of accurate size. Per-2~3 measurement, such as proceeds of c values are equal and equal to the design value, then the vertical installation accurate. For example a, b, and c valueswhile on horizontal vertical errors for measurement, General in iron angle code bit at measurement level points grid errors, specific method is from baseline to methyl vertical box center line distance for a,, to b vertical box distance for b, list can measured22
several group number, then with b ± a, =c,c is is methyl b two vertical box between of accurate size. Per-2~3 measurement, such as proceeds of c values are equal and equal to the design value, then the vertical installation accurate. For example a, b, and c valueswhile on horizontal vertical errors for measurement, General in iron angle code bit at measurement level points grid errors, specific method is from baseline to methyl vertical box center line distance for a,, to b vertical box distance for b, list can measured
%；泥石流是城关区最为发育的地质灾害类型，涉及的区域面积大，危险性高，%；地面塌陷相对影响范围较小，%。
（二）地质灾害成因机制

城关区地处陇西黄土高原的西部边缘与青藏高原的交接地带，区内山高坡陡，沟渠纵横，地质条件复杂，加之坐落在黄河谷地，周围群山环绕，地形复杂多变，明显受地质构造控制。尤其在黄土梁区，滑坡比其他单位发育，规模也比较大，而黄河以北的黄土丘陵区则滑坡较少，多形成崩塌灾害。

城关区地处陇西黄土高原西部，区内地质构造复杂，断裂、褶皱十分发育，除变质岩分区岩石强度较大，滑坡不发育外，岩土体主要有黄土、薄层半坚硬至软弱沙砾岩夹粘土岩岩组（K+E）、层块状软弱粘土岩岩组（N），极易遭受暴雨和水流的侵蚀，形成崩塌和滑坡，为泥石流的形成提供一定数量的松散固体物质。广泛覆盖于基岩风化层和泥岩层上的黄土厚度大、结构疏松、垂直节理发育、空隙大、持水性差、透水性强，地表水极易沿空隙和垂直节理下渗至基岩顶面风化层或泥岩层，使得强度大幅度降低，斜坡稳定性急剧下降，呈现出一系列崩塌、坍塌、塌滑以至滑坡，并以灾害链的形式诱发泥石流等其他地质灾害；第三系泥岩和白垩系的砂泥岩具隔水性，胶结程度低，遇水易软化，甚至泥化，导致强度降低，不仅自身易于滑动，而且其顶面常成为黄土滑坡的有利滑动面。
several group number, then with b ± a, =c,c is is meth