We have been asked via NTC 146 to provide a cost for concrete and for steel H pile supported sewer pipe bridge supports. At the time this request was made we had expected that the steel H piles would be driven but subsequent design work has shown that driving is not possible in most of the bridge pile locations due to the marl being close to the surface and too hard to drive the piles to the required depths.

【翻译】对方已经通过NTC 146，要求我们提供混凝土和H型钢桩支撑的下水管桥式支架的成本。在这一要求提出时，我们此前预计H型钢将被打桩进入，但后续设计工作已经表明，由于泥灰靠近表面，在大多数桥梁桩的位置上打桩是不可能的，很难把钢桩打到所需的深度。

【结构分析】

第一句：We （主语）have been asked via NTC 146 （谓语）to provide a cost for concrete and for steel H pile supported sewer pipe bridge supports（主语补足语）.

这句话的主动语态是：ask sb. to do sth.

1. via NTC 146：通过NTC 146，方式状语。

2. for concrete and for steel H pile supported sewer pipe bridge supports：作定语，修饰cost。

3. steel H pile supported 作前置定语，修饰sewer pipe bridge supports。

第二句：At the time （时间状语）this request was made （定语从句，修饰time） we （主语）had expected （谓语）that the steel H piles would be driven （宾语从句） but subsequent design work （主语）has shown （谓语）that driving is not possible in most of the bridge pile locations due to the marl being close to the surface and too hard to drive the piles to the required depths.（宾语从句）

1. this request was made： 定语从句，修饰time，省略了关系副词when。

2. but 之后的部分是个并列分句。

在but 这个分句的宾语从句中：

3. in most of the bridge pile locations ：地点状语。

4. due to the marl being close to the surface：原因状语

5. too hard to drive the piles to the required depths：too...to...结构，“太难了，不能......”。